Painting over Old Canvases

Painting over Old Canvases

The following is an exchange that raises a couple of common concerns for oil painters:

Dear David,

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, Louise

Hi Louise, 

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:

1.  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.

2.  Rough up the surface with sandpaper to give it ‘tooth’ so the next layer will adhere better.

3.  Dust (vacuum) the surface and wipe it clean with a solvent like turpentine or mineral spirits. 

4.  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

Hi 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

Hi 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