Anyone use gum sandarac?

[Tavy]

I've heard this recomended for mixing with shellac to produce a somewhat harder finish... but anyone use this?

Curiously yours, John.

[Rick Turner]

For another interesting additive for French polish, check out Acryloid B-72, often used in the museum conservation trade.

[sunburst]

I've never used gum sandarac, but if you do some research on violin varnishes past and present, you can learn about myriad exotic sounding additives and what they are intended to do. This stuff goes back centuries, with the results on display on violins that have been around as long, so the risks of using traditional, historic additives are small.

[Austin Clark]

I use about 5-6 grams of sandarac for every 45 grams of shellac flakes in my varnish. There are some gums/resins that work well from historical recipes for varnishes, some not so well. Experiment and see what works for you.

Whatever you decide to add, be sure it is well dissolved and filtered, as most of those resins (and shellac) usually have pieces-parts in them that you don't want in your finish.

[amowry]

I use it too, though I've tried shellac with and without and haven't noticed much of a difference.

I mostly like the smell!

[woodwiz]

To 10 parts shellac, I add 1.5 parts by weight of Sandarac, and 1.5 parts Mastic. Makes a very good spirit varnish, and also great for touchup and French polishing.

For filling cracks, I use shellac and sandarac 50/50, as thick as I can make it and still have it flow into cracks. If you have the right consistency you can run a bead less than 1mm wide, which dries fast (overnight) and is easy to scrape level.

[victor seal]

I use it make a sealer for violins. I don't have the recipe right now, but if you want it I can get it for you. It is easy to make and works great. Vic.

[David Newton]

I have a vague impression that adding sandarac to my polish jobs build slightly thicker, and are slightly harder. I like the smell, and it isn't any more trouble to add it in at about 10% or so. What can it hurt?

Sandarac is listed as the hardest of the natural resins, so it is probably more brittle. Not so good for instruments used alone.
I read somewhere (probably on the internet) that in earlier days it was used alone and was considered the ultimate polish for furniture.

[Tavy]

Thanks everyone: very informative replies as ever!

John.

[David Newton]

Updating this 4 year old thread with a new opinion.
Don't use it.
I have found adding Sandarac doesn't help, and can hurt a French polish job by making it brittle and "flakey"
Much better to use Seedlac or buttonlac, as close to raw, unadulterated Shellac as possible. Filter out the wax, or leave some in, but mixing other resins is a waste of time, in my opinion.

[j. condino]

There is a nice article on the use of sandarac with french polishing mixtures in the current issue of American Lutherie magazine by my good friend Stephen Marchione. Different combinations and proportions with your mixtures will produce very different results, from too hard and brittle, to absoultely beautiful and very durable. Like anything, ask 10 different luthiers and you'll get 14 different answers.

j.
www.condino.com

[Champlin]

Like anything, ask 10 different luthiers and you'll get 14 different answers.
www.condino.com

I had a recent conversation with a luthier who I respect and admire. I was telling him how I wanted to get a more durable finish (I french polish shellac). He suggested adding some copal. I casually mentioned this to another local luthier who I also greatly respect and admire, and he instantly responded.. "Don't put that in your shellac. It will just make it a softer finish."

I guess their opinions cancelled each other out, and I'll just have to experiment and form my own!

[Austin Clark]

FWIW, I no longer use any additives to my shellac. I use good quality alcohol, good quality flakes and FRESHLY mixed product applied VERY THINLY on top of WELL CURED oil varnish. This seems to give the best sheen, durability and longevity I have found for the type of finish process I use. At least for me.....

Most of my builder friends who use shellac finishes are only using straight shellac, too. Some spray and some FP, but they all get good finishes!

But more to the OP's point, haven't really had problems with "1704" type shellac formulations other than sometimes you can get undesired, undissolved solids showing up in your finish. No fun. Lol!

[Bernie Daniel]

To 10 parts shellac, I add 1.5 parts by weight of Sandarac, and 1.5 parts Mastic. Makes a very good spirit varnish, and also great for touchup and French polishing.

For filling cracks, I use shellac and sandarac 50/50, as thick as I can make it and still have it flow into cracks. If you have the right consistency you can run a bead less than 1mm wide, which dries fast (overnight) and is easy to scrape level.

I thought that last point you made about crack filling was very interesting. You did not BTW mention what solvent you used for that. Could you comment on that? Thanks.

I wonder how mixing sandarac with something like nitrocellulose would work as a crack filler? I usually let the nitro evaporate to a thickness of honey to fill cracks. Could a person color or stain the crack-filling mixture the color of the wood finish to make it less visible when done?

Just an addition general question/comment on this natural plant product obtained from a type of Moroccoan cypress tree.

It can mean other things entirely. I first came across the term "sandarac" in a course on inorganic chemistry back undergrad the mid '60's and it was in reference to arsenic sulfides (e.g., As2S3, a yellow mineral historically used as a pigment in paints). So don't buy that when you order! Digression!

Some years later in a course on natural product chemistry in grad school I did come across the name "gum of sandarac" (in fact there was bottle of it in the chemical supply room) as a plant exudate of commercial value as wood finish. It is my understanding that sandarac dissolved with a oil like linseed or tung oil actually cures to a true varnish -- that is when it dries it actually forms chemical bonds -- so it is not re-dissolvable with original solvent. This in contrast to the common evaporative finishes -- e.g., shellac or nitrocellulose.

Is this true? If so if and that is what is meant by calling it "more durable" or harder as a finish is a distinction that might be worth knowing/considering before using?

[multidon]

FWIW Behlen Violin Varnish which is supposed to be a spirit varnish is advertised as consisting of super blonde shellac flakes gum mastic and gum sandarac. I have heard many stories of people trying it once and giving up on it because it dries extremely slowly. One month or even two months later still soft enough to imprint. If sandarac is supposed to make it harder sounds like it doest work in this case.

[Tavy]

FWIW Behlen Violin Varnish which is supposed to be a spirit varnish is advertised as consisting of super blonde shellac flakes gum mastic and gum sandarac. I have heard many stories of people trying it once and giving up on it because it dries extremely slowly. One month or even two months later still soft enough to imprint. If sandarac is supposed to make it harder sounds like it doest work in this case.

Strange - shellac and sandarac French polished or padded on dries hard moderately quickly, certainly within a couple of weeks. Maybe it's the method of application (brushed?) that doesn't let the solvent out? Or else the stuff is sitting around in the jars for too long before folks get to use it. Can't beat freshly mixed up stuff.

[amowry]

I tried the Behlen spirit varnish years ago, and no, it didn't dry hard. It may very well be a freshness issue. I never had similar problems with my own fresh shellac/sandarac mix.

[Frank Ford]

I use sandarac sometimes, but only because it smells so good.

Lots of commercial shellac liquid concoctions don't dry properly because of the wide range of contaminants that are "allowed" - stuff like water, gasoline, wax. And, old shellac undergoes some changes if it sits around too long, losing solubility in alcohol, strength and toughness.