Synthetic Varnish


When I varnish a painting, I don't use damar varnish anymore, I use a styrene resin that has very similar properties, called Regalrez 1094. Unlike damar, it dissolves readily in paint thinner, and doesn't require turpentine. Its main advantage is that it remains soluble indefinitely, rather than bonding inextricably to the paint and changing chemically to be less and less soluble, as damar tends to. That means that if the varnish has to be removed in the future, it can be done easily with a weaker solvent like paint thinner, rather than with difficulty using a stronger one. There are lots of old pictures that have suffered because of this kind of cleaning in the past, especially ones with subtle glazes in the upper layers.

Another advantage to it is that one can varnish a painting sooner. Ideally, one should let a painting harden for six months or more before applying damar, so as to minimize the wrong kind of bond between the two different substances. With this stuff (especially with the proper additives) it is less critical; the painting should be ready when it appears to be thoroughly dry.

They say you can use the resin by itself in solvent, and it still cross-links * with the paint surface less than damar. Ideally, though, it's supposed to be mixed with a rubber compound called Kraton G 1657, which makes it more flexible and very slightly thicker, and a liquid stabilizer called Tinuvin 292, which keeps it from becoming insoluble.

One art supply company sells a partially pre-mixed version of Regalrez, which includes the dry resin and bottle of solvent with the rubber and the stabilizer already mixed in the right proportions. But I buy the separate substances from a conservation supply company, and mix it with paint thinner. I can't imagine why more people don't do this. You get a far greater supply, and the components are separate. This appears to be important, since the stabilizer is supposed to go bad after a couple of years. If this is pre-mixed with the solvent and the rubber, doesn't that mean that the whole bottle has the same limited shelf-life? If you buy the components separately, you might not use up the bottle of stabilizer in time, but at least you won't waste the rubber and the solvent.

                * whatever that means


From left to right: the resin, the rubber blobs, and the stabilizer


How to use Regalrez 1094

You will need:
                -Regalrez resin crystals
                -Kraton G rubber
                -Tinuvin 292 stabilizer
                                you can get these components here, or from a similar conservation supply company
                -Gamblin Cold Wax Medium
                -low-odour paint thinner

                -a glass jar
                -a hot plate or other method of heating something gently
                -a bowl or similar vessel
                -a decent varnish brush

The recommended proportions of the four components are as follows: for the amount of solvent you want to use, you need 20-30% resin by weight. What is more important is the ratios of the other components to the resin; the rubber should amount to 2%, and the stabilizer should also be 2% the weight of the resin. But you can ignore this information and skip to the formula in Step 1.

If you do some tedious measuring and arithmetic, you will discover that each little blob of Kraton G weighs about 0.02g, that the average drop of Tinuvin 292 weighs 0.03g, and that the density of paint thinner is about 0.77g/mL. But you won't have to waste your time with all this stuff, because I already wasted mine.

As you may have noticed, I'm using grams and millilitres rather than ounces and fluid ounces. Although the metric system is pernicious and evil, using it in the studio is convenient and unobjectionable. It also works out very neatly with the little rubber things.

Like damar varnish, Regalrez is very shiny, in many cases unpleasantly so. I used to dissolve a tiny amount of grated beeswax in the mixture to decrease the shine. But this only worked up to a point; if I added any additional wax to the recipe in an attempt to get it more matte, it would end up horribly streaky. I think this may have been because I was using a weaker solvent, but then, I preferred not to use turpentine since it's more damaging to the paint surface.

But now I have a reliable way of making it as matte as I want, by adding Gamblin Cold Wax medium to the mixture. Although it's also made of beeswax, for some reason it doesn't end up streaky, as long you take certain precautions. I have no idea whether other commercial wax mediums will behave the same way. Maybe some day I'll figure out how to do this with raw materials rather than a pre-mixed, Name-Brand substance (as if I'll ever bother), but for now this works really well.


Step 1:

Work out how much you want to make. Here are the final components, in proportion:
                30mL thinner
                6g resin
                6 blobs (0.12g) Kraton G
                1 to 2mL wax medium
                4 drops (0.12g) Tinuvin 292

You can multiply this tiny recipe to get the amount you need. The final volume of varnish will not be hugely greater than the volume of paint thinner. Always make a bit more than you need. I find that the coverage is roughly 0.025mL for every square inch.


Step 2:

Measure out the resin. If you make the above recipe without multiplying it, for small paintings or to experiment with, you will probably want something more sensitive than a kitchen scale to measure the amount in question. Also, Kraton G is sometimes sold in powdered form rather than convenient exactly-2%-of-a-gram little footballs, meaning that you would actually have to weigh it in small quantities.

This is the scale my grandfather used to use for reloading shells.
It's about 80 years old and completely indispensable for accurately
measuring tiny quantities of stuff. So, I'm all right... you're going
to have to buy a lab balance or something.


Step 3:

Pour the thinner into the glass jar with the rubber and the resin, and leave them overnight to dissolve.


Step 4:

The next day, mix the solution very thoroughly. Make especially certain that there are no blobs of rubber left undissolved. Be careful about this, it's often difficult to see.

Add the Tinuvin 292 and the wax medium. Stir them in thoroughly. 1mL of wax medium results in a semi-gloss surface that's about as shiny as I'd ever want, while 2mL makes it very matte. 1.5mL makes a good all-purpose varnish.

By the way, because of the wax medium, you might have realized at this point that you need some relatively accurate way of measuring out 1 or 2mL of a pasty substance. I came up with some weird device made from an old cigar tube and piece of dowel. You'll just have to figure something out.


Step 5:

Heat this mixture very gently on the hotplate, until the cloudiness of the wax clears entirely. If you miss this step of melting the wax, the varnish will likely end up streaky.

Now take it off the heat and leave it until it goes cloudy again. The more wax, the less time this takes; 2mL takes an hour or two, 1mL takes... I'm not sure, but hours and hours. If you miss this step of letting the solution cloud up again, the varnish will end up glossier than it should be.


Step 6:

Make certain the painting shows no signs whatsoever of tackiness or softness in any layers. Just before you varnish it, wipe it with a clean cloth, as lint-free as humanly possible. If the surface has dust and itty-bitty hairs partially fused to it, try removing as much as possible with masking tape or painters tape, or you can wipe it carefully with paint thinner on a clean rag. Both of these should be safe unless there is something really wrong with the paint film.


Step 7:

Even though low-odour thinner is supposed to contain fewer toxic components than regular thinner or turpentine, the space in which you varnish should be ventilated somehow, especially if you are varnishing large paintings. It should be well lit and as dust free as possible. If you can't avoid dust, then at least don't stir it up.

The brush you use has to have stiff bristles, hold a reasonable amount of liquid, and should be as wide as possible. It should be very clean--the standard thing to do is to have brushes specifically for use with varnish and nothing else. I use Chinese bristle brushes which, despite their cheapness and apparent crappiness, have all the necessary qualities once the loose bristles have been knocked out. Some people use those grey disposable foam brushes, too.

Put the painting down flat on an adequately stable surface. If the painting is large, make sure you can easily reach all parts of its surface. The procedure from now on is almost exactly the same as with damar.

Stir the varnish well, and pour it into the bowl. Dip the brush, and tap off the excess on the edge of the bowl. Starting at one end and ending up at the other, methodically cover the entire surface with alternating, overlapping strokes. With each stroke, drag the brush gently across the painting, dispensing varnish in a thin layer which is liquid enough to level out completely, leaving no bristle marks. Reload the brush as often as necessary. Periodically look at the surface from a shallow angle, and use the glare from the lights to check that you aren't missing patches.



Brushing out - no varnish


Repeat this process, but without reloading the brush, and in a perpendicular direction, to ensure an even layer. You can brush it out like this again if you must (perpendicular to the last time), but you have to stop well before the evaporation of the thinner makes the varnish viscous enough to start retaining brush marks. Also, you should leave some time in which you can use a pair of tweezers to pick out any errant hairs from the still fluid and leveling varnish. If I'm not mistaken, this kind of paint thinner evaporates more slowly than the turpentine used with damar varnish, and therefore gives you more time to brush it out and monkey with it.

After half an hour or so, lean the painting face-in against a wall so that it can finish drying without dust falling on it.

Use the rest of the varnish as soon as possible, in less than three weeks, because the stabilizer breaks down in the solution.



Copyright © 2014 by Harry Steen