Expert: Greg Scholl - 5/5/2009

Question
Thank you for your time, I was hoping to get a second opinion. I have a 7 year old
oil painting on a 1/4" birch panel that has cracked. It seems that the wood
absorbed moisture in the summer and when it dried in the fall it cracked the wood
and even the paint. I spoke with someone in art restoration and they advised
soaking the wood in raw linseed oil. It is my understanding that Raw linseed oil
does not harden/ dry. I was told that it would moisturize the wood and may stop
the cracking. So long as it won't hurt it sounds worth a try, what do you think?

Answer
Hi Tricia, when woods cells have dried out so much that the piece has cracked, there's no way to "moisturize" the piece back to it's original state.Any solid wood panel, be it in a painting, furniture, whatever, has to be allowed to move, as they will expand and contract with variations in humidity and temperature no matter what. It's also imperative to use properly dried wood at the right moisture level when building something from wood that will last. Raw Linseed oil will eventually start to get gummy and harden, although it will take a lot longer than Boiled Linseed oil. Will it keep any more damage from happening?...not likely, as it's possible that now that the panel has cracked, it won't be shrinking much more. Is this mounted in a frame? If so, it's more important to unmount it and remount it in such a way that the panel can move across it's grain....and then to be mindful of where it's kept, and most importantly, what the humidity level is in that environment. It's possible that the crack could be joined together and glued, but without knowing the particulars I can't tell you whether that's an option. In the Winter, especially, with forced air heat,etc., we often don't pay attention to the humidity levels in our homes, and frankly, that helps to keep us Restorers in business, because lack of, and wild swings in, humidity....are damaging to Leather, Wood, Paper, Oil paintings on board, canvas, and even us...our skin, nasal passages, etc...also, any 7 year old Birch panel would likely be plywood, not solid wood, so that would be a bit odd to have that crack....most Artist's would seal the back of a painting on board, as that helps to equalize the stresses and moisture release and uptake of the piece...just like veneering...if you're going to veneer one side of a panel, you have to veneer the other as well, if you hope to have it last. They would have likely used shellac or a Damar varnish to seal it. I suppose it's likely that applying the oil to the panel wouldn't do any harm, but(especially if it IS plywood), I doubt you'd get a lot of benefit from it either unless the other steps are taken as well....hope that helps a little....post back if need be..