Hi All,
Periodically I need to make some changes to an already dried oil painting. Usually the painting is only a few weeks old, but sometimes a few months. To date I have either scraped the offending bits off (but this can leave a trough); sanded it off (not sure if this is good for the overall painting) or painted over it with thicker paint (only works where the overlayer is compatible with the rest of the painting…in terms of thickness, opacity, etc.).
Would really like to know if there is a better way and, also, what do you think of my 3 methods above?
Thanks in advance,
PS: I usually paint on gessoed canvas panels, although I sometimes use stretched canvases. In the latter case I would usually hold some firm material behind the canvas so that any scraping/sanding did not stretch the canvas in the local area (unfortunatery this dosen’t always work and I end up with a localized backwards depression in the canvas).
Help!
Many thanks for your excellent detailed advice. I will follow this.
I would probably go with sanding, BUT only if the underlying paint is non-toxic (whatever that actually means) or preferably, you create a situation where the sanding can be done without any possible inhalation/absorption of toxic substances. I have used sandpaper soaked in mineral spirits (wearing gloves) to sand offending areas and then scrupulously wiped away the residue before starting to paint. Please dispose of the residue ethically.
Realize that both scraping and sanding will create a surface that is fundamentally different in texture than the original unless the work was painted on a smooth panel or if the work is very smooth in nature. If it is on a canvas, even a very fine portrait linen, the difference will likely still be very noticeable.
Yes, it is necessary that a rigid surface be placed under a sized, primed, or painted canvas that will receive any substantial pressure like that exerted be scraping or sanding.
As to the failure of your sanding/scraping. It is usually best to place the canvas face up on a table and then build up underneath the canvas util there is a planar rigid surface to resist any pressure that you are applying to the surface. We often use hardcover books to achieve this. It is essential that you do not stress the canvas when performing this operation. There should be no give to the canvas surface. If there is any flexing, add thin magazines or even sheets of paper below the books (you need to maintain the rigidity near the reverse of the canvas) to make sure that the surface does not flex in any manner.
It is quite typical that the offending areas occur over crossbars. When this happens, find a rigid, thin material (like a thin metal plate, etc) and place this over the cross bar but under the canvas (with the painting face up). Then build up the space on both sides of the cross bars using books, etc. so that when the painting is placed face up on a table the canvas is planar, well supported, and the whole region can take pressure without being pressed out of plane.
I hope that is helpful. I am sort of worried that some may take this info, and not following it to the full degree, cause damage to their artworks.
