I read a pamphlet from Gamblin Artist's Oil Colors, which says "Conservation scientists
recommend painters use neutral pH Poly Vinyl Acetate (PVA) Glue size on linen and canvas instead of rabbit skin glue." Elsewhere in the pamphlet they talk about grounds for oil paints, recommending theirs. They say, "Formulated from alkyd resin, titanium dioxide, and barium sulfate, Gamblin Ground makes canvas and linen stiffer than acrylic ground and more flexible
than traditional oil primers. Are they telling the
story straight, or are they leaving-out a few facts
I should know?
Acrylic mediums are a good choice because they become water insoluble and the slight swelling and contraction is far less than rabbitskin glues movement, so it's better.
PVA glue, a.k.a. white glue like Elmers, used as a size is done but honestly it makes me a little nervous. Any school artwork people have ever done using Elmers loses its adhesion after it becomes brittle and there is some movement.
Ideally, a size should not be a thick heavy film. It should penetrate the canvas completely so it is not a film on which the gesso/primer wholly rests upon. You still want the primer to penetrate somewhat and attach to the fibers.
With acrylic medium such as GAC 100 or GAC 700 as the size, followed by acrylic Gesso, heavier coats are O.K. because our gesso has the same binder and everything attaches very nicely. Two coats of GAC, followed by at least two coats of gesso is what we typically suggest to oil painters.
One of the concerns that makes oil painters and conservators leery of acrylic gesso is it's more flexible than the oil paints, and this may lead to tacking. So they would prefer to use a more rigid material to stiffen the canvas.
We don't think traditional gessos (solids and hide glue) are a good idea to use on anything but rigid panels, so it narrows the choices on stretched canvas to those with some flex and resistance to cracking. Lead white and oil are mixed and used for this. The lead white pigment does a good job of absorbing the oil and drying relatively quickly. It's usually applied fairly heavily and this thickness offers some resistance to subsequent oil paints but it has a natural tendency to crack as it cures and embrittles. We think the concern is when these layers start to crack, everything on top also cracks.
The new binder for oil painting is Alkyd resin. Commonly, this is a soy bean product, but it can be made from other nuts and things. Supposedly alkyds are a superior resin to linseed and walnut oils because they are designed to remain more flexible over time than linseed oil, and this should improve the aging characteristics.
The use of Titanium Dioxide and Alkyd as an oil painting ground makes sense, so we don't see any problems, and Gamblin is a great company with a dedication to artists. They are heavily banking on the success of the alkyds, as all of their mediums are made from it.
We have been working on developing new products and practices for the oil painter and hope to introduce some in the future. Lots of testing needs to be done. However, one of the things we like to work on when oil painting is our Molding Paste mixed with a little gesso to lighten it up. It has marble dust solids in it which give films a rigidity without a concern for cracking. It may be something for you to consider trying. To sum it all up, we think a lot of acrylics are lumped into one general category and they have no idea of all of the paint lines, gels, mediums and other products.
After building up a texture on a primed canvas, can you paint over it with oil paints?
First, the canvas or support should be coated with 1 or 2 layers of GAC 100. This sizes the substrate to prevent oil penetration. Next apply 1 coat of Gesso, then the Molding Paste as desired. Some artists will apply another coat of Gesso over the Molding Paste, to increase tooth and whiteness, but we do not believe it will be necessary, as Molding Paste is already toothy. Allow several days for the acrylics to cure, perhaps longer if you have applied them very thickly, or if you are working on a wood panel or other support that allows the acrylics to dry through the front.
I paint with oils over GOLDEN High Load Acrylic over gesso on polyester canvas. Is this archival?
I use an oil-based lead white primer on cotton canvas sized with rabbit-skin glue for oil painting,
but am concerned about the hygroscopic nature of the glue size. What can you recommend I use in place of the glue?
I am hoping to use your Matte Medium in place of gesso as a ground for painting in oils over cotton duck. Is there anything I should know about using this method? Will it need some fine sanding as it does with gesso prior to using the oils?
I was wondering if it's possible to add anything to your regular gesso to make it more sandable and less plasticky? It sounds as if your sandable gesso is safe to use only on rigid supports but can it be added in small amounts to the regular gesso for priming canvas and linen?
Can you use acrylic primers under oil paints?
First, it is our belief if the oil painter is concerned with creating artwork that will last for as long as possible, the artist should first select a rigid support such as birch plywood to either paint directly on, or stretch a canvas over and secure it. We don't think anyone will debate an aged oil paint film is going to crack if flexed, so why give it the opportunity? The use of a panel also ensures less exposure to moisture from the backside of the canvas. Not only does this reduce the chance of swelling of acrylic polymer or rabbitskin glue sizing, but it prevents the elements from breaking down the fibers of the fabric. Secondly, The surface should be properly sized according to the kind of paints and how these paints are going to be used.
Rabbitskin Glue is used traditionally as a size for oil painting as it reduces the ability of the acids in the linseed oil from coming in contact with the fibers. If allowed the acidic nature of linseed oil will break down the fabric causing it to crumble.
Acrylic polymer mediums such as GAC 100, have been tested for preventing oil penetration and for a phenomenon called Support Induced Discoloration (SID). When the GAC 100 is applied sufficiently, typically 2 brush coats, it prevents the oil from penetrating and it greatly reduces SID in acrylic paints and mediums. SID is when water-soluble impurities such as dirt or glues in the support are pulled into the acrylic film during drying. This causes a discoloration such as yellowing, that is most pronounced in glazes or straight gel layers. The use of an acrylic size also ensures the beginning of a bond between the support and subsequent priming/paint layers.
Third, use a quality primer. Acrylic gesso comes in many forms. Some artists will skimp on materials at this stage and use either a student grade version, or even house paint. Some gessos on the market may also be too thick or too glossy to be of great benefit to the artist. Others, usually bargain gessos, have an overload of solids and are under bound. The resulting film simply isn't a durable film, and is most likely very susceptible to moisture. If a poor grade of gesso is used, it won't matter how great the paint is; the entire painting layer is at risk of delamination. A proper gesso or primer, needs to have certain qualities to ensure long life of an artwork.
It needs to be thin enough to penetrate the weave of the canvas. It needs to be made with a proper solid to binder ratio. The solids used must generate the proper tooth to sustain a "Lock and Key" effect for the paint layer. If the subsequent paint layer, regardless of whether it's oil, acrylic, or whatever, isn't being applied in a lock and key manner to bond the two layers together, the layers may separate over time.
Additionally, the acrylic priming layer needs to have been fully cured before painting with oils or alkyds. Although acrylics dry very quickly, many people assume they are cured when touch-dry. Acrylics actually can take several days or even weeks to cure to the point where all of the water and additives have escaped the film.
In acrylic paintings, the curing time isn't as critical because the priming and paint layers are similar. But because there are two very different chemistries involved between oils and acrylics, it is paramount you do everything possible to make sure these layers are interwoven, and sufficient time has been allowed for proper curing.
Fourth, oil paint application is important: not only to achieve the proper primer and paint bond, but also because it's vital to the life of the painting. There has been much discussion of the kind of oils used in paintmaking and medium use, but we have not seen much about the proper oil painting fundamentals. Perhaps many have taken these for granted that everyone knows them. Fat over Lean. Slow drying over fast drying. Thick over thin.
The chemistry of oil paint demands these principles be followed, or suffer the consequences. We believe many artists have long forgotten these things, or worse, they have never been taught them. To me, this is just as important to creating long lasting artwork as the priming.
Oil paints have been used for a long time, but there has been a lot of conservation done to keep most of the great works viewable. There is a lot of recent artwork in oil that is only a few decades old and requires great attention. Ask any conservator.
Fifth, varnishing is important. Varnishing isn't just for you to get the final sheen you desire, although it is one function. Varnishing is meant to protect in the long haul of things. A good varnish job does not detract from the artwork and goes on almost invisibly. This layer is going to protect your artwork when we're all long gone. Varnishes are removable coatings and many have Ultra Violet Light Stabilizers to slow fading down.
Finally, paintings need to be in a good environment during their life. If it's meant to last, humidity and temperature fluctuations can spell disaster. You may not notice it in the next couple of years, but in the long haul, this leads to premature cracking, cupping and then delamination well before the materials can endure. This has been long-winded, but we think the question goes well beyond "Can I use acrylic primers under oils?" The answer is not a simple yes or no, as there are many factors to consider.