Oil and cotton again

 

Oil and Cotton again...

Hi David,

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.

 

Hi,

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.