I have fabricated canvas frames out of 2 x 4 Douglas fir with a 1/4 “ skin wood front. I am in need of a solid surface due to the weight of the mediums that I will be applying in addition to the hardware I want to use to mount the metal. It is my plan to stretch and adhere a cotton canvas over the wood. My question is….how should I treat the wood to ensure that the acidity of the wood does not damage the canvas. Do I need to treat both sides of the wood? I have considered painting the wood with gesso and then using either Gel medium or paste to act as an adhesive before stretching the canvas over the wood and gessoing the canvas. Do you have any suggestions for applying the canvas to the medium and stretching? Do you suggest using staples as well as medium?
Any concerns with drilling screws thru the canvas and into the wood? Thanks, Lisa
You are doing all the right things. You definitely want to seal the wood so that the acid does not travel into the canvas and thru to the painted surface causing support induced coloration (SIDS). I wrote an article about that a while back (Nov/Dec 2003). Gesso won’t do the trick to seal the wood as gesso is very porous. Instead, you can use wood shellac (preferably white shellac) from the hardware store to seal the wood first. The other option would be to apply a couple of coats of Golden’s GAC 100 medium or even Acrylic Matte medium first. If it is hardboard or a wood product with a smooth surface, before adding any size (shellac or acrylic medium) you should sand it first so that the canvas adheres well to it.
Once the board is sized use the gel medium to adhere the canvas to the board, then you can go ahead and gesso the canvas. you do not need to treat the other side of the wood because of SIDS but it would be a good idea to put a coat of size there too to prevent the wood from absorbing excess moisture (which will cause swelling and cracking). This will also help prevent mold from attaching itself to the back.
Cut the canvas a couple of inches larger than the board. To glue the canvas to the board apply a generous amount of the gel medium all over the surface of the board, at least 1/8” thick. Then lay the canvas on and start smoothing it out from the centre towards the edges. Use a trowel or flat piece of word or stiff plastic for this. Some of the gel medium will squeeze off the end of the board, use this to attach the excess canvas to the back and you can reclaim the rest. There is no need for staples.
I would do a test with the screws to see if they would rust under the medium. Just cover some screws with gel medium and check back in a couple few weeks. You can also buy galvanized screws that have a rust-proof coating.
Good luck Lisa, it sounds like a fun project. David
A: When you paint on a surface with oils, acrylics, tempera paints, or various collage techniques, be it a canvas, panel, or paper, you must first prepare that support with a coating that has the ideal properties to hold onto the paint. This coating keeps the paint from coming into contact with the support. This insulating layer is called a “ground.” Paintings should not be done directly on a canvas or panel without a ground because if the support deteriorates it will damage the painting. Sometimes a conservationist is required to separate a painting from its support if the later is no longer stable. If the painting is attached directly to that support you can see how this would be problematic. This does not apply to watercolor paints or pastels which are attached directly to the paper. There is the issue of the various names for the different types of grounds, and sometimes this can create some confusion…
“Gesso” is the name of the traditional ground made of Calcium Carbonate (chalk) and Hide (animal) Glue. It is not flexible and can be only be used on rigid supports. Its use dates back hundreds of years and was a favorite of Tempera painters who loved to have a very smooth finish. Some artists still use it for this reason and it can easily be made at home with materials available in most art stores. It can be built up and sanded between layers (as many as 30!) to create a painting surface that is almost a smooth as glass. In recent years manufacturers of acrylic paints have been making Acrylic Polymer Gesso and this product has all but replaced the original variety. It too is called simply “Gesso” most of the time. It uses polymer resin as a binder instead of hide glue so is more flexible and can be used on either rigid or flexible supports.
”Primer” is the name used to denote a lead-white-in-oil ground used for oil paintings. For centuries painters used the Hide Glue Gesso on wood panels, or a Lead Oil Primer on canvases. Now the Acrylic Polymer Gesso has replaced both for most artists. Most art supply stores will sell an oil based primer and some manufacturers have changed the original formula by substituting Titanium and Zinc for the lead white pigment and Alkyd Resin for the Linseed oil. Still others have simply used zinc and/or titanium instead of the lead white and useSafflower Oil instead of Linseed oil. This last formula would not be as flexible or durable as either of the other two. It helps to check the ingredients of the various products before you buy.
So “gesso” refers to the water based grounds, that is, the traditional hide glue/calcium carbonate or the modern acrylic polymer variety, while “primer” is the name reserved for an oil based ground for oil painting.
opinion about linen glued to hardboard (such as Masonite) as a support for
oil painting? I haven’t tried this yet – I was thinking of using Lascaux 498 HV Adhesive (from Prochade). However, I understand this glue has
water in it and must be treated with Xylene before adhering canvas to wood.
Can you recommend a glue?
Yes linen glued to hardboard is a good permanent support for oil painting -provided the right adhesive is used. Once to linen is attached it can then be prepared like any other surface to receive the paint.
I would use PVA (polyvinylacetate). The ph neutral archival variety can be bought in most art supply stores. I would then put a coat of the PVA on the front of the linen and then two or more coats of acrylic gesso.
Is it sound, from an archival point of view, to seal a hard wood panel or masonite panel with acrylic gesso, if you intend to paint in acrylics? I’m wondering about water molecules getting into the board.
Hardboard is an excellent, permanent, rigid support for oil, acrylic, tempera, or mixed media work. Yes it is sound from an archival point of view to use acrylic gesso as a ground. But there is more. You do need to first seal the board with a size so that the water from the gesso does not get into the wood. The water will often come back through the gesso later bringing with it acidic impurities from the wood. These will change the color of the gesso/paint (brownish/yellowish). This phenomena is known as SIDS (Support Induced Discoloration). See my article on SIDS in the Nov/Dec 03 FCA Magazine.
You can use a thin coat of pure resin Shellac to seal or ‘size’ the board first. Pure White Shellac diluted 3 parts Methyl Alcohol (Hydrate) to one part Shellac is a good formula. You can actually purchase both the Shellac and the Methyl Hydrate at most hardware stores. You can also use the Golden GAC 100 as an alternative size before applying the gesso. Although the GAC 100 is a water based medium, it is quite impermeable when dry.
Here is an excerpt from an instructional paper I wrote that describes how to prepare a painting panel:
How to Make a Painting Panel
Supplies you will need:
Untempered hardboard cut to size, White Shellac or Golden GAC 100, Methyl Hydrate, a wide brush, no. 60 or 80 sandpaper, Acrylic Gesso.
1. Buy Untempered Hardboard. You can get smooth on one side or smooth on both sides. Hardboard comes in two thicknesses, 1/8” and ¼”. For paintings up to about 16×20 I use the thinner 1/8”, and for sizes up to 20×30 I use ¼”. It comes in 4×8’ sheets and most hardware stores will cut it for you for a fee.
2. Sand the smooth surface before sizing. No.60 or 80 sandpaper is good.
3. Size both sides of the panel with a mixture of 3 parts Methyl Hydrate to 1 part White Shellac. Apply the shellac in a thin layer in one stroke of the brush or roller. If you apply too much size the surface will become too shinny and smooth and the gesso will not adhere well to it, then you will have to sand it again. If you are using the GAC 100, put 1 coat on the back and 2-3 on the front, you can thin it with a bit of water (up to 20%) to help it spread if you need to.
4. Apply the Acrylic Polymer Gesso on each side of the panel, one coat on the back and at least two on the front. If you want a very smooth finish you can sand with fine sand paper, 200 grit or higher, between each coat after it has dried. You can use an inexpensive gesso on the back since its only purpose there is to keep the panel from warping, and a premium quality gesso on the front. You will find the best gesso will have more covering power and better adhesive strength.
I read your answer to Esmie’s question re: priming canvases in the latest edition of Art Avenue. I went to Golden’s website as you suggested but now I’m confused. You state in your reply to coat the back of the canvas with GAC 400, and to put one or two coats of GAC 100 over the gesso on the front of the canvas. On Golden’s website they say that GAC 400 can be applied to the canvas to stiffen the support before gesso application but don’t say that it should be applied to the back of the canvas, and they go on to say a two coat application of GAC 100 is recommended before applying gesso indicating that the GAC 100 is under the gesso while you said the GAC 100 is applied over the gesso.
Currently I am applying two coats of gesso to my canvases but after reading your article I think I should take even more care to practice sound archival techniques. I want to be sure that I’m doing it the best way possible and was wondering if you could clear this up for me.
Yes I can clear it up for you. Esmie’s question was about what to do with commercial ready made, primed canvas that already has a coat of gesso.
In your case you are preparing your own canvas so you can follow the instructions on the Golden web site: the GAC 100 would go on the front of the canvas before the gesso. I prefer to apply the GAC 400 on the back because it gives the fabric added protection against environmental pollutants and moisture.
Thank you for your recent advice in Art Avenue about oil painting on cotton canvas. My question is what do you recommend to prepare linen surfaces for oil painting? I have stretched linen over Masonite and over stretcher bars and have coated the front of the canvas with rabbit skin glue or Gamblin PVA (Polyvinyl Acetate) before applying an oil painting primer (Gamblin Oil Painting Ground). What do you think of these methods? Do you recommend others?
Thank you, John
The methods you describe are standard practice for preparing linen for oil painting and have been proven reliable by the test of time.
The PVA is a modern, upgraded substitute for the traditional hide glue (often called ‘rabbit skin’ glue). I say upgraded because it will not become brittle over time as the hide glue does.
I would not hesitate to recommend the method I described for preparing cotton canvas, using Golden’s GAC 100 and 400 mediums that is, for painting in oils. And as anyone who has stretched both cotton and linen canvas will know, stretching cotton is easier than stretching linen. Linen is much more expensive than cotton as well. The method described above gives cotton all the desirable qualities that have traditionally made linen the fabric of choice for permanent painting in oils.
As for attaching canvas to Masonite (hardboard) I am also comfortable using acrylic mediums and gesso for oils. Because you are painting on a rigid surface the problem of the oils separating from the ground/fabric are not an issue as they would be with a flexible support (canvas).
I read with interest your art techniques column (Sept– Oct of Art Avenues) and have a further question. If you use a commercial canvas from the store and coat it with gesso and then coat it with acrylic paint will it be satisfactory to paint with oils on it? I have painted for a long time and have not come across artists who are
using your method with the GAC unless I am unaware of it.
I would appreciate a reply.
You are right, I haven’t come across any either. Artists are not often taught about materials and techniques anymore.
An extra coat of gesso and/or acrylic paint will help, but only marginally. After the oil paint layer has dried it loses most of its flexibility. If the canvas moves, flexes, expands and contracts, the gesso/acrylic paint, which stays flexible indefinitely, will move with the canvas and the dried oil paint layer will inevitably crack, separate from the acrylic paint or gesso layer, and lift. Many artists use acrylic underpaintings for their oils and I recommend that this practice is best performed on a rigid surface instead of a flexible one like canvas.
If you are already putting two layers on top of the already gessoed canvas before painting then I suggest that you follow the method outlined above.
I read your recent article in ‘Art Avenue’ with great interest. You have provided answers to several questions that I had meant to ask you after your previous article. I have another question related to this very topic:
Is it ‘safe’ and ‘useful’ to apply GAC 400 on the back of the
finished oil paintings? I have painted many oil paintings without
following the detail recommendations you have raised in your article.
No, it is not safe. The GAC mediums, like all acrylic mediums, are water based. If you apply any acrylic medium to the back of the canvas the water will travel thru the canvas and may cause lifting of the oil painting.
A: Yes, it is true. That is, if you want your paintings to last for a few decades at least. Oil eats cotton. Cotton canvas for artist’s is unbleached and is a cream color and has little brown flecks in it. Linen is a darker brown, burlap colored fabric, and is more expensive. Linen is a much more durable fabric for a couple of reasons. The fibers that make up the material are longer and rounded, like tiny ropes. Cotton fibers are short, flat strands of unprotected cellulose fiber and are spun together to make up the fabric. Because the linen has linseed (flax) oil in the fibers (this gives it the dark color) the fabric is more durable and is protected from pollutants and moisture in the air. Cotton readily absorbs moisture from the air. This causes it to expand and contract more than linen. As you can imagine, this would not be good for dried oil paint. The absorbent cotton canvas is also more prone to deterioration from any substance that comes into contact with it, like acidic oils (the paints), sizes, or oxygen and pollutants in the air.
A cotton canvas coated with acrylic gesso (which is also porous and absorbent) will suck the linseed oil out of the oil paints. If you look at the back of most oil paintings done on cotton canvas you will see dark patches of oil that have soaked through to the fabric, especially if the paint is applied thick. This acidic oil will then ‘eat’ away at the cotton fibers and the fabric will become weak and brittle within a few years. Worse yet, now the paint layer has been robbed of vital oil that is needed to keep the colors bright and transparent, and the paint layer flexible and durable. I have seen oil paintings on cotton canvas no more than ten years old that are dried out, dull, and cracked throughout. Many artists like to use the ready-made cotton canvases at the art supply store. These are made with very thin cotton (around 6-7oz.) and are coated with a thin layer of very absorbent acrylic gesso that is spayed on – a quick snack for a robust oil painting… The bad news is if you want to make permanent oil paintings on canvas you are going to have to spend more money and you will have to make the canvases yourself, or have them custom ordered or custom made.
Besides cotton and linen there are also some composite fiber canvases out there that are mostly mixtures of synthetic fabrics like polyester and sometimes linen. These are probably good choices for oil painting.
This next question follows up this discussion:
Q: what type of primer (ground) should I use for painting in oils? Is Acrylic Gesso alright?
A: Oil paints can be safely used on hardboard that is prepared first with a size (a thin layer of White Shellacdiluted 2 parts Methyl Hydrate – 1 part Shellac is a good choice) and at least 2 coats of acrylic gesso. You can buy the shellac and the methyl hydrate thinner at the hardware store. These are the only products that you can use in permanent painting techniques available at hardware stores! Latex house paint is not a good primer! These commercial paints are not designed for artist’s purposes and are specifically engineered to deteriorate after a few years.
Oil paints will probably not adhere well to acrylic gesso on canvas. Imagine what happens to a dried layer of oil paint on a plastic bag that is being stretched. This is an exaggerated example of what would likely happen when the canvas expands and contracts. The best flexible support (canvas) for oil paintings is linen (or one of the newer synthetic fabrics) sized with Poly Vinyl Acetate (PVA) then coated with an oil ground (primer). You must let the primer dry thoroughly for several weeks before painting.
Recent research and development has seen changes, and improvements in the products used to prepare canvases for oil painting. Animal hide glue, generically referred to commercially as Rabbit Skin Glue was the size of choice for hundreds of years. The purpose of a size is to protect the canvas from coming into contact with the oil from the primer/paint layer. The disadvantage of the animal glue is that it absorbs and releases moisture causing it to expand and contract. This of course may cause cracking in the paint layer. Hide glue also yellows and becomes more brittle with time. Its modern replacement is the PH neutral PVA that can be used on both sides of the canvas to both insulate it from contact with the oil and protect it from atmospheric pollutants and moisture. It is available in art supply stores. The other modern innovation is an oil primer that uses an alkyd resin instead of the traditional linseed oil as a base. It dries quicker and is more flexible.
So go to the art supply store and spend some more money! If you want more detailed instructions on how to prepare a gesso panel and canvases for oil and acrylic paintings drop me a line or I may post the info on the FCA website… thanks for the Q’s.
I just read your article on Art Avenue. You mentioned that oils over acrylic paint is safer if done on a rigid surface rather than on flexible surface like canvas. How about painting oils on canvas that has been primed commercially, for example, the kind that DeSerres makes? Is that ok? Also, is layering more gesso on these primed canvases helping the binding of oils to the surface?
Does the same apply for acrylics on gessoed canvases that were previously primed?
Thank you for sharing your wisdom and expertise with all of us.
I will answer your question as a follow up to the last article. I have covered this topic in previous issues over the years but it is a good time for a review – it is the most frequent technical question asked by painters.
Most artists use commercially made pre-gessoed canvases like the one you mention, and unfortunately they are not a permanent support for oil paintings. Oil eats cotton. A cotton canvas coated with acrylic gesso will suck the linseed oil out of the oil paints. If you look at the back of most oil paintings done on cotton canvas you will see dark patches of oil that has soaked through to the fabric, especially if the paint is applied thick. This acidic oil will then ‘eat’ away at the cotton fibers and the fabric will become weak and brittle within a few years. Worse yet, now the paint layer has been robbed of vital oil that is needed to keep the colors bright and transparent, and the paint layer flexible and durable. I have seen oil paintings on cotton canvas no more than 20 years old that are dried out, dull, and cracked throughout.
So adding more gesso to the already primed canvas will not do so much to help the oil adhere as it will protect the canvas from coming into contact with the acidic oil paint – and this is a good thing.
There is an even better solution of artists wanting to paint in oils on ready made cotton canvases. The Golden acrylics company has done much R&D in this department and have come up with some excellent products and strategies for making cotton canvas more permanent for oils. Check out their website (goldenpaints.com) for some excellent technical information.
They recommend coating the back of the cotton canvas with their GAC 400 medium, which is a fabric stiffener. This serves to keep the fabric from flexing under the dried oil paint. It also makes the fabric less absorbent for moisture in the air. The front of the canvas can be coated with the GAC 100 medium that will make the canvas/gesso less absorbent so the oil paint will not soak thru to the canvas.
Here is a step by step procedure for preparing ready-made, pre-gessoed canvas for oil painting:
1. Coat the back of the canvas with one or two coats of GAC 400
2. Put one or two coats of GAC 100 over the gesso on the front of the canvas
3. Add another layer of acrylic gesso on the front for the paint to adhere to.
That should do it. This is the best solution I know of for painting oils on cotton canvas.
By the way, the same does not apply for acrylics on pre-gessoed canvas. You can go ahead and paint right on them with acrylic paints without concern. Acylic will remain flexible and are not acidic so will not harm the fabric.
Very few companies are making an oil based primer for linen these days. The two companies that I know that make it are Fredrix and Gamblin. These products are an alkyd based primer that uses titanium dioxide and zinc white pigments instead of the traditional lead white pigment. These newer alkyd primers actually dry faster, are less yellowing, and are at least as flexible as the traditional lead primer. Also, it has become too expensive for most companies to import lead because of high tariffs for transporting toxic materials. This is probably one reason why it is also harder to find lead white paint (“cremintz”, or “silver” white as it is sometimes called) for oil painting. This is a harder to replace though. Lead white is the fastest drying, most flexible pigment in the palette and it has a rich, buttery texture that is unmatched by any other pigment. It imparts these same qualities to any color it is mixed with. Alkyd based paints, though they make an excellent primer, do not have these same ‘painterly’ qualities when made into tube colors. The concern over using toxic materials in the studio has also discouraged many painters from using this excellent white paint. Remember though that most colors in the palette are toxic and some highly so (cadmium, phthalocyanine, etc), and they all need to be treated with the same care (check out “Toxicity” in the may 2000 issue).
Right. So, back to painting in oils on cotton. The Golden company (acrylics) has been doing some research on painting in oils on cotton canvas. A good thing since that is the common practice of most painters, and a good thing for Golden since they make acrylic products. Here is a quote from the their website:
“To date, the best system to both stiffen the canvas and block oil penetration is to apply 1-2 coats, or a front and a back coat, of GAC 400 to develop the stiffening of the fabric. Once dry, apply 2 coats of White Gesso or GAC 100 to the front to achieve the oil blocking properties, and allow to fully dry.”
Here they recommend the GAC 400 instead of the traditional “Rabbit Skin Glue” or the more modern PVA as a size for the fabric. The reason the fabric needs to be stiff is to minimize movement and flexing of the fabric. This, as we already know, is very disruptive to dried oil paint films. It is just nice to have another option for those who are interested in permanent painting in oils. Thanks for the questions.
A. It is hard to say. These materials are designed for commercial/industrial use and are not made with permanence in mind. Plexiglas does break down, yellow and become more brittle with age, I am not sure about fiberglass. The strong epoxy glues used to make fiberglass may break down in time. The other concern is the permanent adhesion of the paint to the surface. Plexiglas is fairly inert but paint (oil or acrylic) will not adhere well to it unless it is treated to give it more ‘tooth’, sanded or etched with a sand blaster for example. Fiberglass is more porous than Plexiglas as a rule but I am not sure I would want my paint coming in direct contact with it (because of the unstable nature of the epoxy mentioned above). You might consider some isolating varnish that would adhere well to the fiberglass before painting on it. The Golden paint company makes a medium that is designed specifically for this purpose, it is their GAC 200 medium.
I received the new issue of FCA magazine which had an article by you regarding oil painting supports. I am quite disturbed by this as I wonder if all the paintings I have sold will soon disintegrate!! Please help me figure out if I am still okay. I paint with water miscible oil paints on pre stretched canvases that are gessoed with acrylic gesso three times. Once from the factory and twice by me. I paint in very thin layers, even the first layer. There is no impasto. I see no leakage to the back on any of my paintings. Question: If I buy the pre-stretched canvases with the one layer of gesso and add my own layers of PVA and oil ground on top, will this be okay? Can the PVA be used on canvas as well as linen? Can you buy pre-stretched linen canvas? Where? You also say that there is an alkyd resin available- does this take the place of the PVA or is it in addition to? Please send me as much information regarding supports, especially those already made up – I am not prepared to start making my own. Thank you!!
I am sorry to be bringing the bad news to you, and to many others who are concerned about the permanence of their paintings. It is unfortunate that such basic technical information is not common knowledge with artists. We are trying to fix that problem.
Your paintings, as you describe them, will be as permanent as any oil paintings could be on cotton canvas. I am sure they will last a long time. It is a good idea to put the extra coats of gesso on the front. I think that your other ideas may be a further improvement as well…
I have seen pre-stretched linen on canvas in stores. You can ask at your favorite art store if they can get it in for you. Have you considered painting on hardboard instead of canvas? It is more stable and permanent than cotton or even linen for oils. I know that some painters prefer the texture and surface tension of canvas better for their style of painting. They sell ready cut and primed pieces of hardboard (sometimes called ‘door skins’) at opus I believe. An extra coat or two of acrylic gesso, just like you do with the canvases, would make a permanent painting support for oils.
Yes you can use PVA on cotton as well as linen. It is a good idea to coat the ready-made canvas, front and back, with the PVA, then add the oil ground on top. Putting a coat of size (PVA) on the back will protect the fragile cotton fibers from deterioration from exposure to the elements and it will make it less hydroscopic (water absorbent) so that it will not flex as much. Dried layers of oil paint become brittle and hard and don’t really like to sit on flexing surface as you can imagine. The alkyd resin primer IS the oil ground and it replaces the acrylic gesso ground, not the size (PVA). For those who are concerned about using lead white oil grounds you can check the ingredients on the can. Most oil based primer using alkyd resins don’t use lead white anymore.
I hope you feel better Donna, if you have any more Q’s please drop me a line.
I’m trying to get started painting on hardboard, so today I went to Home Hardware and got some 1/8″. I asked for the kind that did not have oil in it ( you said it was the light kind), and the clerk said that the 1/8″ stuff I bought was not tempered. It’s still bugging me, though, because it looks dark to me (and it was darker than the 1/4″). What do you think? I don’t want my painting to peel off in a year or something!
If the clerk says that it is untempered then it mostly likely is. Hardboard comes in different shades of brown depending on the source. If you are still uncertain, ask to see some ‘tempered’ hardboard (with oil in it) so that you can compare. That way you will see how different it looks and feels and be better able to judge for yourself in the future.
Seems I have a little dilemma with my older works, when I started to paint. I used hardboard for the support WITHOUT applying any gesso. Therefore I have acrylic paints directly applied to the hardboard. My question is in regards to some sort of final coat, should I apply medium as an isolation coat and then a varnish over this, as the process which you’ve taught. My paintings these days are properly executed right down to the Golden MSA Varnish. Also whether there will be any longevity with the acrylic onto the hardboard. I have sold some of these early works, without any sort of finish and have another five in inventory, which I’d love to still show in hopes of selling. Do you suggest I apply the medium and varnish front and back? I don’t feel great about selling artwork below a professional level but I do need to include these paintings in my body of work to sell.
The problem of putting the paint, or gesso, directly on the hardboard without first sizing is that the acidic properties of the wood will migrate into the paint layers. This can cause some brownish discoloration called SIDS (support induced discoloration) that may be visible in the light areas of the painting. I don’t think it is a big factor with regards to the permanence of you work but i don’t know for sure if any conservation research has been done on the long term effects. I would varnish just like any other acrylic painting (isolation acrylic gloss medium varnish, then a layer of acrylic solution varnish like the Golden MSA). I would put a coat of Golden GAC 700 or White Shellac on the back.
Hi Again David,
Thank you for your reply David, the information is useful, particularly re other artists selling works in a worse state than the ones I speak of. Nonetheless, it is precisely the professional longevity
and quality of producing works I am interested in and your advice and knowledge base, which you generously share, is very much appreciated. May I add that I am unclear when you refer to sizing. Is this different from gesso? Also, the GAC 700 on the back, I had been applying the same base as the isolation coat on the face. Is the GAC a better sealant, less costly or ?. Thanks for your clarification on these questions.
Hi again Denise,
A size and a primer (acrylic gesso in this case) are different. They serve two separate purposes. A size is for sealing a surface to prevent physical and/or chemical interaction from happening between the gesso/painting and the support. The hardboard is acidic and you don’t want it to come in direct contact with your work so you size it, or seal the surface. The gesso serves as a ‘ground’ that provides an ideal physical surface (the paint adheres well to it), and optical surface (usually white) for your painting to be applied upon. Most paintings supports require both a size and a ground (gesso) because you rarely want your painting to be permanently affixed to a support, it makes future restoration more difficult for one thing.
I recommended the GAC 700 as a size for the back of the panel because it is a better sealant, less absorbent that is, than the regular gloss medium that you are using for the isolation varnish – though it is more expensive. For the back of the panel the difference is not important however, I would use white shellac that you can purchase at the hardware store.
Q: What does “permanence” mean?
A: If a painting maintains its original appearance for 100 years without cracking, fading, sagging, and so on, it is considered permanent. If the canvas or panel that you paint on deteriorates, the painting itself will also suffer.
Q: Should I paint on a flexible or rigid support?
A: Oil paint becomes harder and more brittle with age and is therefore more prone to cracking. For this reason a rigid support is a good idea for oil paintings. Acrylics have not been around for hundreds of years like oils but scientific analysis and accelerated aging tests show that it will likely remain flexible indefinitely, like most plastics. For permanent results, acrylics can be painted on a rigid or flexible support, like canvas or paper. For sizes larger than about 20×30″ rigid supports made of wood or wood fibers are quite heavy and more subject to warping. It is recommended that you glue a wooden frame (cradle) to the back of large panels to prevent warping.
Q: Do I need to size the canvas or panel before putting on the gesso ground?
A: Yes. Except for painting with acrylics on canvas or paper where it is not essential for permanence. Wood or wood products are acidic and the fibers will swell when a water based ground (gesso) or paint is used on them. A coat of sizing is designed to create an isolating barrier between the wood and the paint or ground and to regulate the absorbency of the wood. It is a good idea to put a coat on both sides. For any type of painting or collage on panel a thin coat of white shellac (diluted 3:1 with Methyl Hydrate) is a good size. You must be careful not to put it on too thick or the surface will become too smooth and the ground will not stick well. Oil Paints are also acidic and will cause canvas to deteriorate if it comes in contact with it. Here again the size acts as a protective barrier. The best material for sizing canvas for oil painting is hide glue. For Acrylics a coat of acrylic gloss medium is best and a coat on the back of cotton canvas will protect the fibers and make them less absorbent.
Q: Why is the ground important?
A: The ground, called a “Primer” for oil paintings, provides the ideal surface and absorbency for the paint to adhere to. The white surface of the ground ensures that the colors retain maximum luminosity as well. This is particularly important for oil paints which become darker and more transparent with age.
Q: Is acrylic polymer gesso a good ground for oil paintings?
A: It is difficult to say if the oil used to make the paints and the acrylic resin in the gesso will form a permanent bond since they are so different in their chemical and physical properties. When used on a rigid support like hardboard the oil paint will probably stay put. On canvas that moves it is more risky. Imagine how dried oil paint would react on a plastic bag that gets stretched. Because the acrylic gesso is more absorbent the oil in the paint seeps through to the canvas and will cause it to rot. The oil deprived paint also becomes more brittle and dull looking. This principle also applies to the common practice of painting in oils over an acrylic underpainting. For permanent painting on a flexible support the best choice for oils is linen canvas with the traditional hide-glue size and an oil based lead primer.
Q: What is the difference between the traditional gesso and the new acrylic polymer gesso?
A: For hundreds of years artists painted on panels using a simple gesso made of hide glue and calcium carbonate. It is the same hide glue used to make the size. This gesso is very absorbent and can be applied in very thin layers and sanded between coats to achieve a very smooth painting surface, more so than with acrylic gesso. The traditional gesso is very absorbent and needs to be sized before applying paint or it will absorb too much of the binder from the paint. The acrylic gesso substitute is made of acrylic polymer emulsion with calcium carbonate and some titanium dioxide and zinc oxide to make it whiter and give it more covering power.
Q: How about using Latex house paint as a ground instead of gesso?
A: This is acceptable for any painting that you don’t want to last. Artist’s materials are made with artists’ purposes in mind and for permanence. Industrial or commercial materials are made for other purposes and will have unpredictable results. Most house paint is specifically engineered to deteriorate within a few years so that is can be replaced.
Q: What is the difference between cotton and linen?
A: Unbleached cotton for artist’s canvas is a cream color and has little brown flecks in it. Linen is a darker brown, burlap colored fabric. Linen is a much more durable fabric for a couple of reasons. The fibers that make up the material are longer and rounded, unlike cotton fibers that are short and flat. Because the linen has linseed (flax) oil in the fibers, this gives it the dark color, the fabric is protected from pollutants and moisture in the air. Cotton is composed of unprotected cellulose fibers so it readily absorbs moisture from the air that causes it to expand and contract more than linen. This is not good for dried oil paint. The absorbent cotton canvas is more prone to deterioration from any substance that comes into contact with it, like acidic oils, sizes, or oxygen and pollutants in the air.
Q: Can I paint in acrylics on cotton and get permanent results?
A: Yes. Acrylic polymer mediums, paints, and gesso will even act as a plastic protection for the cotton canvas. Because acrylic paints remain flexible they will move with the canvas. A good practice is to coat the back of the cotton canvas with gloss medium to protect the fabric and make it less absorbent.
Q: What is the best product for a rigid support?
A: Untempered Hardboard. Masonite is a brand name commonly used to refer to this product. It is inexpensive, very durable and easy to work with. Hardboard is wood fibers compressed under pressure with the natural glue of the wood (lignin) serving as a binder to hold it together. When properly sized it is very permanent. The temperedhardboard has oil added to make it water-resistant so it not recommended for use as a support because the ground and paint layers will not adhere well to it. To prepare the hardboard panel, sand the smooth surface and put a thin layer of White Shellac on both sides. Then at least 2 layers of gesso on both sides. Other wood products like Chip Board and Melamine are heavy. Plywood is likely to warp, crack and separate as the glue between the layers dries out and all of these products are more expensive than hardboard. Hardboard panels are easy to ship and frame as well.
Q: How about a summary of some good choices for permanent painting?
A: For oils, acrylics, tempera paints, collage and mixed media, hardboard panels are excellent. Size them on both sides with White Shellac and at least two coats of gesso. In sizes up to about 16×20 1/8″ hardboard is good unless you are doing very thick acrylic paintings or collages. 1/4″ hardboard will be stable without warping too much up to about 20×30.” For oil painting 24×30 or larger linen canvas sized with hide-glue and coated on with a lead white ground on the front only is the best choice. For acrylics or mixed media on canvas, use cotton, linen or synthetic fabrics sized on both sides with acrylic gloss medium and gesso on the front.
MDF & HARDBOARD
I realize that it’s almost sacrilegious, but I prefer using MDF boardrather than Masonite for both direct gesso and painting, and for wet mounting paper. Liquitex literature seems to condemn both the tempered and un-tempered versions of Masonite and suggests MDO board as a better alternative.
I’ve used MDO board (sign painters plywood) for a while now but havebeen put off by the fact that it’s availability in one sided or doublesided paper backing (I prefer double sided) is totally random from thesupplier in my area.
MDF board due to it’s construction properties (smooth both sides) seemsto have less warpage problems that Masonite, and it’s lighter colourrequires less gesso coverage.
The additives in the tempered version of Masonite is why Liquitex warnsacrylic painters against this product. I’m wondering if the same warningshould be given for MDF board because of chemical properties that it mightcontain.
Tempered Masonite (hardboard) is impregnated with oils to make it more suitable for outdoor construction use. Because of this, paints won’t adhere well to it and the oil is very acidic and will discolor the gesso/paint. Regular hardboard is the only wood product made with pure cellulose material (wood) with no other additives, so it is the only one I would recommend as a support for permanent painting. MDF is made with synthetic glues and resins and although it does not warp as easily as hardboard I question the permanence and chemical stability of some of these products. If the hardboard panels are not too large (18×24 and smaller) they will be not warp once they are in a frame. Plywood panels, sometimes called ‘door skins’ are made with thin layers of veneer held together with glue. The glue will eventually dry out and cause cracking and separation of the layers.
Hope that helps, David
I have done my first ‘real’ painting on hardboard and I hung it on our office wall and I noticed it is ‘lifting’ at one corner – bottom right (not laying flat any more). I glued basic braces at the back to start before painting – 1by2 strips around the edges and one cross piece. Is there any easy way for me to now flatten it out without framing it? Overall painting is 48 inches high and 44 inches wide. I thought you might know the easy answer (and a way to avoid it in the future).
And I must once again thank you for inspiring me to begin painting w/ your great workshop. I don’t think I will ever stop now!
I am very happy to hear you are a non-stop painter now! Well done! I love the paintings.
Hardboard does have a tendency to warp, especially when they are larger. Here are some guidelines:
-for large paintings on hardboard you need to use the thick 1/4″ board, not the 1/8″.
-for paintings more than 30 inches, braces on the back like you describe are essential if they are not framed, but the braces have to be thick enough. You can screw another 1by2 strip to the one already there, that should help.
-the back of the board can be treated with wood sealer, like shellac, to help prevent it from absorbing moisture, which will cause it to bend.
-do not hang a heavy painting using a wire, too much pressure. Instead use two hooks on the wall, one for each side.
first, thank you so much for being so generous with your knowledge and experience – I really appreciated finding the answers to many of my questions on your website.
I’ve been a fulltime printmaker for the last 13 years (etchings) and am just turning to oil painting. My questions are around the painting supports. I don’t like canvas or MDF – and really want to paint on wood. I’ve been doing my practice work – value studies etc on pine planks primed with acrylic gesso. However for work I intend to sell and from reading your site it seems I really need to move to hardwood. I live in New Zealand and can get hold of recycled rimu – a very slow growing and straight tree – so hopefully the same quality as the hardwoods you suggest.
We need to be very clear about what hardboard is. It is not ‘hardwood’ and certainly not MDF. Hardboard, the most common brand name is Masonite, is a wood product made from fine wood fiber (sawdust) compressed under enormous pressure. The natural glue in the wood, lignin, is what holds it together. It is just cellulose fiber (wood) with no added glues or waxes like other wood products you find at the hardware store.
Hardboard is durable and structurally stable. If you like painting on hard surfaces then hardboard is much more permanent than almost any product available to artists, certainly much more so than cotton canvas, particularly for oil paintings (see the Q&A page on my website for more info on this).
It comes in 4×8 ft sheets at the hardware store and usually 2 thickness, 1/8 and ¼ inch. Do not use the ‘tempered’ hardboard as is suggested by one of the writers on the forum you linked, the tempered variety is impregnated with oil to make it more water resistant for outdoor construction use and the oil will cause serious problems for you painting.
See below for answers to your other questions:
1 – I’d like to use shellac as a size – but have come across contradictory advice on the internet.
Shellac is a good product for sizing wood panels. You have to make sure it is pure shellac and not a commercial, industrial product that has various additives. Dilute the shellac with Mythyl Hydrate (alchohol), also available at the hardware store where shellac is sold, 3 parts to 1 part shellac.
2 – What is the difference between using amber (yellow) shellac and bleached shellac?
The yellow stuff is the natural color of the resin and is more suitable for our purposes, they use heat to bleach the shellac and that makes it less usable for artist’s purposes. That said, the Golden GAC 100 medium is an excellent product for sizing.
3 – If a hardwood panel has been sized on all sides with shellac – does it still need a primer coating on all sides or just the painting side and the edges?
Remember, hardboard, not hardwood. Hardwood panels made from thin layers of wood have resin canals and are often laminated (like Plywood) and the glue holding the laminates together is not permanent. Yes, prime both sides of the hardboard panel to keep it from warping.
4 – Would you recommend oil primer over acrylic gesso for oil painting – and are there problems with getting the oil primer to bond securely to the shellac which is smooth and shiny?
This is very important – the size layer, be it shellac or GAC 100, should only be applied thick enough to seal the wood, it should not be thick enough to create a smooth shinny layer or the gesso will have no ‘tooth’ to adhere to. Acrylic gesso will always adhere better to the GAC 100.
You don’t need to put both acrylic gesso and oil primer, one or the other will do.
5 – In terms of hanging I’d like to use just the board – they are 2.5cm thick – without a frame – however if I simply screw in hanging triangles to the back won’t that allow moisture into the wood? What would you suggest?
Again, you are talking of hardwood laminated panels (plywood) so if you choose to use those then yes you can hang them without a frame. If you size the back, moisture will not be a problem.
Painting over old oil canvases
The following is an exchange that raises a couple of common concerns for oil painters:
I have many old oil paintings over which I would like to begin new oil paintings. I prefer to start with an all-white canvas. Is it OK to paint over the old painting with an oil-based alkyd ground?
Thanks for your attention to my request,
I have a question for you. Have you found any oil/alkyd ground for artists? I would like to know if there is any other source cuz I have only found one so far. As for your question, it is an ok idea but not a great one if you are concerned about permanence. Oil paintings that are simple, relatively thin layers painted over a flexible ground/primer (like the oil modified alkyd primer you mention), and preferably on a rigid support, or linen, have the best chance of avoiding cracking or flaking as they age. The different layers that you are proposing, however, primer/paint/primer/paint, may not be as stable.
As well as questionable adhesion of the new painting on the already used canvas, there is the concern of the old painting showing through.
All colors are transparent in varying degrees and oil paint becomes more transparent with age (and darker and more brownish in hue) so your new painting would get darker with age as the first painting shows thru more and more. This phenomenon is called ‘pentimento’ and it can be seen in old paintings where the artist painted a subject on top of an already painted background thinking they would be covering it up. Also, the brush strokes and texture of the old painting may interrupt the new picture’s surface.
Having said all that, here is the best way to go about it to minimize later troubles:
- Scrape off as much of the old paint strokes and impasto as you can with a palette knife. Use a flexible razor or blade to remove as much of the old paint as possible without scraping the ground itself. You may need to place a board under the canvas to keep it from sagging while you scrape.
- Rough up the surface with sandpaper to give it ‘tooth’ so the next layer will adhere better.
- Dust (vacuum) the surface and wipe it clean with a solvent like turpentine or mineral spirits.
- Apply a thin coat of white or light gray paint, or primer.
It is very important to remember that when you are scraping, sanding and cleaning the surface, that pigment particles that are potentially highly toxic will be stirred and you must contain these and not breath them. I recommend using a vacuum cleaner and dust mask.
hope that helps Louise. cheers, david
Thanks a lot for your reply. Perhaps I should not have called the alkyd primer “oil based.” What I have is “Beauti-Tone Alkyd Primer Sealer Undercoat” from Home Hardware. It is cleaned with mineral spirits.
Alkyd appears to be a major ingredient in many oil paint mediums, but using the primer mentioned above over old oil paintings does not follow the rule of ‘fat over lean.’ Perhaps this doesn’t matter, if the old paintings are thoroughly dry and the primer is considered like a glaze. What do you think?
Also, what about using Gamblin Ground instead? It too is alkyd-based. The bottom line is that I’m just trying to get the canvases back to ‘white,’ without the expense of using oil paint from the tube.
Thanks again, Louise
You are right, the fat over lean rule only applies to undry layers of paint. The rule also says it is not good to put a brittle layer on top of a more flexible layer, you can imagine what would happen. But the alkyd primer is quite flexible.
As for the alkyd sealer undercoat from Home Hardware I would not advise that you use it if you want your paintings to last. These commercial products are not made with permanence in mind and usually contain several ingredients that may have unpredictable results when used in conjunction with artist’s materials. In the case of painting over old canvases, however, permanence is not usually a primary concern and you may want to go ahead and try the commercial primer. The Gamblin alkyd primer is a good product but it is expensive too, about $80 Canadian a quart! – but that will go a long way… hope that helps, bye for now, David
>I was reading your article on painting to insure permanence (100+ years) Applying paint on canvas or hardboard. I am considering painting on plastic or Plexiglas/fiberglass. How long will it last? Acrylic? Oil?
it is hard to say. these materials are designed for commercial/industrial use and are not made with permanence in mind. plexiglass does break down, yellow and become more brittle with age, I am not sure about fiberglass. the strong epoxy glues used to make fibreglass may break down in time. the other concern is the permanent adhesion of the paint to the surface. plexiglass is fairly inert but paint (oil or acrylic) will not adhere well to it unless it is treated to give it more ‘tooth’, sanded or etched with a sand blaster for example. fibreglass is more porous than plexiglass as a rule but I am not sure I would want my paint coming in direct contact with it (because of the unstable nature of the epoxy mentioned above). you might consider some isolating varnish that would adhere well to the fibreglass before painting on it. perhaps an acrylic solution varnish available at the art store. good luck!
I am an FCA member. I like to do an acrylic underpainting (grisalle then basic color), then finish the painting in water soluble oils. I like to use acrylic for the under-painting because of the fast drying and ease of correction. As per your advice, on multi media board I use 2 coats GAC 100, 2 coats gesso.
I have several canvases from the art store that are gesso primed. Your last letter said these are no good with oils as the oil will figure out a way to get to the canvas. Can I coat these with GAC 100, and then re-do with gesso and expect longevity? Maybe I should reserve these canvases and stick to acrylics alone on them. If I am to use canvas as a support for H2O sol oils, should I start buying canvas in the roll and stretch it, then use the GAC and Gesso? I assume that “gesso” means acrylic gesso.
When you buy a wood panel, I assume the masonite panels at the hardware store are not acceptable as they are either tempered, or untempered,
one of which is wrong. I would think the way to go is to buy the panels at the art store and coat them. Do these need the GAC 100? Once again, I thank you for your time and patience.
Good questions and valid concerns as many painters like to use acrylic underpaintings with oils.
Your method of preparing the panels is fine with two coats of Golden’s GAC 100 (this acts as a size/sealer on the wood panel) and then the gesso. You can buy untempered hardboard at the hardware store and prepare in the way described above without a problem. You can also buy the hardboard panels from the art supply store already primed and ready to paint on for your convenience. Some art supply stores sell the unprimed hardboard that still needs to be coated in the way you describe – GAC 100, then gesso.
Longevity is always a concern when painting oils on canvas, they will endure better on a rigid surface like hardboard, especially with an acrylic underpainting. Still, the best option if you prefer to use canvas is to prepare the ready made and primed canvases by first applying two coats of Golden’s GAC 400 on the back of the canvas, this acts as a fabric stiffener and helps minimize movement and flexing of the canvas which is not good for the dried layer of oil paint. Then proceed, as you describe, by adding two coats of GAC 100 on the front, over the gesso, then add another coat of gesso on top of that. This is the best possible option for painting oils on canvas and is accepted as such by most conservationists now. No need, therefore, to stretch your own canvases if you don’t want to do that. And yes, I always mean acrylic gesso, unless I state otherwise.
Be sure to check out my website, davidlangevin.com, where you can find an archive of technical Q&A’s.
Have fun painting, David
What in your opinion/experience is a professional finish to a painting?A finish that a collector would consider a sound investment? Specifically:If a Gallery wrap, with edges Gessoed in black, is it important to have therear gesso edge (closest to the staples) clean, or can it show stray brush marks or does it matter? What information do you put on the back of the painting? Title, your name, date, copyright, medium, inventory number, size? Is this info written on the canvas or on the stretcher bars? If on the canvas, what is used to write it? Pencil, paint? What should an artist avoid doing?
Thanks so much, M
The backs of my paintings are often a total mess, streaks, brush marks and splotches… so no, I don’t think that matters. If the painting has the sides finished with paint, or compositional elements, and perhaps will be hung unframed or in a floater frame, then of course those sides should be well presented.
– On the back I put my name, the title of the painting and the medium (oil, acrylics), and sometimes varnish information. I usually write the size too. Things like inventory number may be part of an artists way of managing and keeping track of their inventory, that is fine, I just go by title. I got out of the habit of putting the date on the painting a few years ago, unless it is relevant to someone who is buying the piece. I have images of my paintings cataloged by date so it is easy for me to figure out when they were painted if the need arises.
– I usually write on the part of the canvas that is attached to the stretcher frame, along the top and bottom, where there is normally enough canvas overlapped. I use an india ink (pigment based ink) marker, or acrylic ink, or sometimes I use acrylic paint and a brush to write the info. It is OK to write on the canvas behind the painting, which I sometimes do, but I would not do that with any kind of marker or ink that is dye based and can seep thru (bleed) – acylic paint and a brush would be the best option for that imo.
– I think it is a good idea to coat the back of canvases with acrylic medium. It protects the fabric from moisture and gives it increased flexibility and durability. Golden’s GAC 400 is the best option but regular gloss medium will do. If the painting is done on in oils then this process is a must for permanence and the GAC 400 would be the optimal choice as it also stiffens the fabric, and dried oil paints don’t like the canvas moving around under them.
– Museums and major art galleries generally protect the backs of the canvases with a material like foamcore or coroplast which is attached to the back of the stretcher bars. This protects the back of the canvas from damage during shipping and handling and keeps it clean as well. They will usually make small holes to allow moisture to dissipate as well so the back of the canvas is not completely sealed.
-The practice of sticking brown paper to the back of paintings that is commonly practiced is not a good idea for valuable art work. There are a couple of reasons why the paper is not recommended. First, it tears easily and is not sturdy enough to protect the back of the canvas from physical damage during handling; it is acidic and therefore deteriorates and falls apart within a few years and there is a chance of paper getting caught between the canvas and stretcher bars; because it is paper it absorbs moisture, which is not good for canvas as it causes flexing of the fabric and mold.