Cooking oil varnish.


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I`m giving oil varnish another try after switching to spirit 10 years ago.

In the past I tried the Fulton varnish which as I recall after adding the linseed oil had to be cooked to the point of being very hard when cooled down--almost to a resin.

I`m gathering as much info now on copal,colophony, mastic and sandarac/linseed oil varnishes and find many of the recipes say that at the point of adding the linseed oil to "Bring it to a boil" and then after cooling to a certain temperature to add turpentine as a thinner, cool down, let settle and is then ready for use.

Is bringing it to a boil for a short time enough? It seems cooking it until it is almost as a resin before adding turpentine would make it dry better, not to mention give it much more color.

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Certain resins demand cooking to form a varnish in which the oil and resin are chemically connected, indicated by drops of the hot varnish making long spiderweb fibers when touched; others do not. I think you need to first determine the composition of your varnish, and then decide on the cooking.

Mastic, dammar, and some of the non-fossil copals don't always need to be cooked at all. Amber, fossil copal, rosin and some of the others require cooking to the fine thread stage. Lacking information it's always better to assume such cooking is needed. Just heating does not lead to the necessary chemical interactions. This is done for the physical characteristics of the varnish, not drying.

Additionally, other things happen during cooking to, as you guess, improve drying, including gassing off of various solvents and waxes which slow drying, and advancing the oxidation stage of the oil--giving it a head-start in the drying process--but those are separate issues.

You will find sandarac listed in many old oil varnish recipes, but I've never seen it successfully made into an oil varnish. There's some doubt whether what's listed in the recipes is what we now know as sandarac. I'd be careful with that one.

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I want to comment on the subject sandarac.

I have a copy of a very old German book: Otto, J. A. - Ueber den Bau und die Erhaltung der Geige und aller Bogeninstrumente, Halle und Leipzig, 1817

(On making and maintenance of the violin and all other instruments of the violin family)

Very surprising to me was Otto's comment on the Cremonese varnish: "The old makers used 'Bernsteinlack'". That means amber-varnish. There was no doubt for him, no "we don't know actually, but we assume ...". It was a fact for him, 70 years after the end of the Cremonese golden period.

Maybe this is a mistake of translation: In Venice where spices, wood and resins could be purchased in those days "bernice" was said to be sandarac. Maybe this was mixed up with the German "Bernstein" (amber).

The old makers used sandarac varnish and not amber varnish? I don't believe either. But maybe this hint is useful for some people here at the pegbox.

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Thanks for the feedback Michael. I noticed the sandarac problem in several recipes and will pay attention to it.

I guess I am most concerned with the cooking of the linseed oil to get it to dry faster and think the other resins may have to be cooked at different temperatures before mixing.

I`ll get back to this tomorrow when I have more time.

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Unfortunately, Otto qualifies with most of the characters of his time as having a different attitude than we do about details. Appearing to know was much more important than knowing. The violin literature of the past is littered with garbage from people like him who turned their speculations into fact. The Hills were a real turning point in violin literature...... and that's another subject.....

Gary Baese is the only person I'm aware of who's written much about the origins of the word "varnish", which he maintains was perhaps derived from a ancient city in Africa named, essentially, Bernice, which apparently was important in the resin trade. Since I've never seen this one anywhere else, I wouldn't bet the farm on it, however.

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Michael, you are right ("The violin literature of the past is littered with garbage from people like him who turned their speculations into fact.").

Otto's writing did not impress me very much. The only point is that he was not too far away in time from the decline of the Italian violin making. But this may not have any importance.

The Hills in 1902 appeared to be the first to do real research and their book is still important today.

To Chris: Bernice, barniz, varnish and Bernstein (amber): correlations are very likely. Who knows?

Concerning Bease's book I have another remark: I cannot believe that he found so many recipes from the baroque time which obviously others before him could not find.

And Bease is completely shure that the violin varnish contained amber. Why?

Amber is hard to put into a varnish, it is no soft resin, it cannot be solved in alcohol and so it has nearly the opposite properties of the old Italian varnish components.

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I am away from my studio at the moment, but upon my return I will post a excerpt from an interest early twentieth century varnish formulation book. The technical varnish info is of little relevance to makers, but there is a very complete etymology of the the word varnish that some here might find interesting.

I must second Michael's experience with Sandarac in oil varnishes. Every other resin has been fairly compliant, but Sandarac seems to have a bad habit of clumping in a large stickly pulp (regardless of fusing). This is too bad, as it has a lovely natural color when heated. If anyone has any tricks for getting it to meld with oil, please speak up.

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Michael,

At first I`m planning to make it with linseed oil and colophony as I guess this is similiar to doing the Fultan varnish which I`m familiar with making and I`d like to add mastic and copal as well.

Some fast initial experiments show no problem dissolving the colophony, mastic and linseed oil together but I suppose it`s not neccesary to add the copal until later on as it may not need cooking.

The thing I am wondering about most is if I am fusing a resin into the linseed oil which doesn`t need to be cooked to the fiber stage or maybe shouldn`t be---then should I cook the linseed oil portion first to the fiber stage and than add the other resin(s)?

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Kevin, re:"I must second Michael's experience with Sandarac in oil varnishes. Every other resin has been fairly compliant, but Sandarac seems to have a bad habit of clumping in a large stickly pulp (regardless of fusing). This is too bad, as it has a lovely natural color when heated. If anyone has any tricks for getting it to meld with oil, please speak up."

I had the same problem. But it seems somebody may be doing it somehow. Here`s a site that sells oil varnish with sandarac in it: http://www.violinvarnish.com/varnishes.htm

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here`s a site I came across that has some interesting reading on varnishes, resins and mediums.

I have been wondering about this MeGilp medium since reading about it in the artists handbook the other day and wonder if it would have any possible applications in texturing varnishes for antiquing purposes.

the site: http://www.jamescgroves.com/mediums.htm

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Japes,I`ll take Michael`s advice on the colophony and not use it until I have researched it more, or probably just end up using mastic and or copal---this is what it seems to be getting narrowed down to.

The Fulton terpine resin varnish does however go into detail on how to process turpentine so that it can be cooked into a resin. As I recall he mentions A and B type resins and the one being used in the process is the oppposite of rosin (and colophony?) I used this varnish for quite sometime but it was alot of work and after moving to a much more humid climate gave up on it as it took so long to cure. Otherwise it was ok.

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Hi Kelvin, re: sandarac. I mix sandarac with roughly equal part of balsam (North American equivalent of Venetian turpentine) which I collected from trees around the house. The cooked down resin is very similar to the cooked down amber in terms of varnish making. Sandarac by itself is good for making spirit varnish, but difficult to dissolve in turpentine. (you could use spike oil first, then add turpentine)

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