Several important issues have been brought up in this thread, and I think they bear discussing in maybe a bit more depth for greater understanding of the archival aspects of the various substances and practices involved. As Bill said, damar is not the ideal varnish for oil paintings, for the reasons he's stated.

Damar discolors, which means that it will need to be removed some day, and since it becomes increasingly insoluble with time, stronger and stronger solvents must be used to remove it, which solvents will also probably take off some paint as well as the varnish unless it is done very carefully by an expert conservator who knows the tricks of the trade. Here are some tips for removing old damar varnish from old oil paintings. First, though, do not try this on any but your own paintings, unless you have been trained as a professional restorer. We can always fix our own paintings if we screw them up, but if we "fix" somebody else's painting by painting on it ourselves, we have compromised the authorship of the resulting image as the work of the original artist.

A very important consideration is to start with the mildest solvent, which would be odorless mineral spirits, and keep a container of it, and some cotton balls, at the ready. OMS will not remove damar, nor will it attack oil paint films that are more than two years old. The reason to have it handy is to stop the action of the stronger solvent after it has done what you've employed it to do, before it has a chance to attack the paint. If damar is not too old yet, English distilled or double-rectified spirits of turpentine might soften it, so that should be tried before any stronger solvents. Apply it gently with a cotton swab, beginning in an area of relative unimportance, to see if it will take off the varnish. It will take a bit of time, so do not be too hasty. Never use a solvent that is any stronger than necessary for the procedure, and always have a cotton ball saturated with OMS at the ready to stop the action of the other solvent. If you see color other than yellowed or embrowned varnish or dirt on your cotton swab, immediately wipe the whole area with the OMS-saturated cotton ball, and then follow it with another one. Conservators will have a range of solvents right next to them when they clean old paintings. This will include mixtures of solvents, to adjust the strength of each. They will always start with the mildest one, and then gradually work their way up until they reach the one that will soften the varnish. Different varnishes require different strength solvents. With damar, the older it is, the stronger the solvent required to remove it.

Many of the solvents restorers work with are highly volatile and involve a risk of fire, as well as health consequences from breathing the vapors and from contact with the skin. These things are best used in environments where the risks are lowest, i.e., with good ventilation and a fire extinguisher handy, nowhere near anything that could ignite the vapors. I do it outdoors when I must use a solvent. I have a box of surgeon's gloves handy, and replace one as soon as it develops a hole. These solvents can get through the skin and into the bloodstream, and they are not good for you.

Bill might have been able to dodge the bullet on his painting if he'd had a cotton ball saturated with OMS on it to stop the alcohol/acetone before it ate into his paint. Fortunately, it was his painting, so he could fix it.

Before modern science brought us better resins for varnishes, damar was a necessary evil. It was an improvement over mastic, which shares most of its faults and has an increased tendency to "bloom" in humid environments. Gamvar is better than any of them, and perhaps its greatest asset is the fact that it remains removable with mild solvents that will not eat into dried and cured oil paint films. It is not expected to discolor, either, so the main reason why anyone would want to take it off is probably not going to be there.

Then there is the issue of natural resins in our painting mediums, added to the paint. There are several potential problems involved here. When these resins discolor, as they will, the discoloration is not reversible the way it is with linseed oil. If it's in the paint, it cannot be removed the way it can when it is a varnish on top of the paint. Secondly, these substances become increasingly brittle as they age, and will increase the tendency for cracking. On rigid panels or canvas glued to panel, this is less of a problem than on stretched canvas, but in any case it is unnecessary. And when there is damar or mastic in the paint layer, and one or the other of those resins is also used as a final varnish, the likelihood is greater that the solvent used in to remove the varnish will also eat into the paint and take some of it off, too, as it did with Bill's painting. One might get by with it if the final varnish is a modern synthetic that does not require such strong solvents to remove, but why take the chance? Linseed oil works well as a medium. Rembrandt is a good example of what can be done with oil paints without resinous mediums added. He did pretty well, in my estimation. I don't know if Bill was using Maroger medium back in the 1970s or not, but if there is any significant percentage of it in the painting he mentioned, that could well have been a factor. I know he uses very little medium, whatever he uses, and that is the best way to use a medium -- very sparingly. Most people use too much medium, and that makes for weak, problematic paint films. From an archival standpoint, linseed oil is probably the best medium to use with oil paints, but it's important to not thin oil paints too far with anything, even linseed oil.

Many of the problems that result from ill-advised choices of materials and methods of application in oil painting do not show up until the painting is 50-150 years old, so it can be very misleading to look at a 20 or 30 year-old painting that still looks pretty good and conclude on that basis that it will never develop any defects. The future is probably going to see some fine paintings suffer from various maladies resulting from materials choices made by the artists who created them. I hope Bill Whitaker's work is not not among them, because he's a top-level Master whose work I have admired from the first time I saw any of it. I'm always reluctant to comment on his choices of materials or procedures because of my respect for him, but he asked me in a private e-mail to come here and add my thoughts on this subject.

Virgil Elliott

Gamvar over Damar?
 

Hello,

I was about to varnish my first oil paintings, but then I saw this thread! I see the argument to use something like Gamvar instead, but I am hoping to quickly get a temporary varnish on a painting in order to show it and liven up the colors that dried dull. I bought some damar varnish for this purpose, intending to dilute it with turpentine.

Can Gamvar be diluted to use as a temporary varnish? Can I use the damar for the temporary varnish, and then use the Gamvar later as a final varnish?

Lacey,

You didn't say how recently the picture in question was painted. Oil paint takes a good while to cure, months after it seems to be dry, and it is best not to varnish it until it's fully cured. A premature varnishing interferes with the process of curing, which involves the incorporation of oxygen into the paint layer. Gamvar should be used at the strength that results from adding the precise amount of solvent that's in the bottle that comes with it to the resin crystals in the jar. I wouldn't recommend using it in any other way.

Whether diluted damar used as a retouch varnish would prove problematic in the long run would depend on several things, but if the painting is important to you, it would be best to leave damar out of it, and let it cure for several months before giving it a final varnishing with Gamvar. Don't be in too big a hurry to show it, if it doesn't look good without varnish on it. Six months goes by pretty quickly.

Virgil Elliott

While it's probably better not to fool with retouch varnishes and the like, I can understand why one would want to quickly simulate varnish like conditions particularly where clients are concerned.

I discovered in Gamblin's "Notes of Special Interest" you can in fact make a retouch varnish by mixing "1 part Gamvar Varnish with 5 parts Gamsol or other high quality OMS."

The question then arises whether in 6 months time the Gamvar retouch should be removed or left on before varnishing with the full strength product.

Also in his notes Gamblin mentions using cold wax medium as a matting agent. When I see the word "wax" I think of Reynolds and his questionable practices. Perhaps when wax is used in varnish as opposed to medium it's another story.

Scott,

There would be no reason to remove Gamvar retouch before applying full-strength Gamvar as a final varnish. The solvent in the final varnish would soften the retouch layer and allow it to become part of the final varnish layer. It wouldn't be a good idea to try to remove varnish from an oil paint layer that's less than two years old, anyway. Chances are some paint would come off in the process.

Wax in the varnish, used as a flatting agent, would not be harmful the way it would as an ingredient in the paint.

After an artist has painted his or her heart out on a painting, it seems wrong, to me, to then do something to compromise its longevity out of eagerness to put it out there right away. For people who cannot wait to get rid of their pictures, there is the option of painting in alkyds, acrylic, pastel or watercolor instead.

Virgil Elliott

Agreed Virgil but will using retouch varnish seriously compromise the longevity of a painting? Are Conservators saying this now, because a few years ago it was advocated, at least here in Europe.

Kind of reminds me of the doctors who warned against butter suggesting margarine was a better alternative and then latter olive oil and now no oils. What is the truth? What do you think they will be saying about Gamvar in ten years time? (I won't know because I probably will have died from an olive oil induced coronary.)

Scott,

Many questionable practices are or were advocated by one person or another, and it could be very confusing taking them at face value, since they are not all in accord. What one can do to sort things out is to consider the fundamental principles involved. Vegetable oils "dry" by a process that involves the absorption of oxygen, which takes place over a long period of time. It makes sense that to place a barrier of varnish between the paint layer and the air before this process is complete would surely interfere with the proper drying/curing of the paint. To what extent this would manifest itself adversely is an open question, but why risk harm to our own paintings?

Virgil Elliott

This is something to think about. I'm certain I'm not the only artist who retouches before a painting goes out the door. I appreciate the information.

Thanks to all
 

This has been a great source of information for me. Unfortunately, I learned to paint with oils before I learned anything about oils.

It was only a year ago that I thought it was O.K. to use Turpenoid Natural as a medium! :o

When I want to deliver a recently completed commission that has sunken-in dull areas, I "oil out" those parts of the painting with a 50% linseed/50% OMS mixture, rather than using any type of retouch varnish. That evens out the surface quite well and dries to a nice semi gloss finish.

Virgil, does this seem like a sound practice?