Studio Notes

I found this interesting article - notes from a talk with a conservator. I have no idea how old it is, nor confirmed all the info - so there's my disclaimer. But this part was of particular interest and I wanted to share:

VARNISH

As mentioned earlier, damar varnish can be difficult to remove from a painting without damage when aged for a long period. This becomes especially true when large amounts of damar have been used in the painting itself.

For safety sake, if one wishes to use damar in one's medium, then a synthetic varnish is advisable. Catherine highly recommended Gamblin's "Gamar" varnish. Other synthetics may still crosslink with the paint film underneath. But Gamar is a hydrocarbon based varnish that does not crosslink and removes easily with mineral spirits (which do not dissolve damar). Also, it does not yellow or crack.

Another benefit is that Gamar is flexible enough to be applied as soon as the painting is dry to the touch, instead of waiting 6 to 12 months. This means that artists can apply a full final varnish before rushing paintings out the door to galleries. Catherine says that no varnish seals out air from a painting, and that immediate varnishing will not hinder oxidation of the paint layers beneath.

Gamar comes as crystal resin and solvent that must be mixed and dissolved by the artist by shaking hourly for 8 hours. This is due to it's limited shelf life. One container of Gamar will cover 80 square feet of surface area, so an artist may want to save up a group of works to varnish at once, or else mix smaller portions for use, since it should be used up within a month of mixing.

The gloss of Gamar is meant to be comparable to damar, but some say that it is shinier. To reduce gloss, add solvent (mineral spirits) or wax medium.

No resin protects against oxidation or atmospheric moisture. Its sole purposes are to protect against dirt and atmospheric pollution, and to even out the sheen of a painting, adding depth to color.

* I don't find a Gamar from Gamsol - they have GamVAR - so I think this is a typo on the author's part. Or they've renamed their product.