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murray kuun

OIl or spirit varnish?

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11 minutes ago, Michael_Molnar said:

Yes. The low pH phenols in tannin (tannic "acid") can react with normally stable  red ferric oxide changing it to black ferrous oxide. However, if you isolate (encapsulate) the iron, it will remain stabile. 

How would one go about that? Probably not by encapsulating it in violin varnish, which tends to end up with some fissures or porosity.

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13 minutes ago, David Burgess said:

How would one go about that? Probably not by encapsulating it in violin varnish, which tends to end up with some fissures or porosity.

Right. You can only encapsulate a ground pigment. For varnish, I lime it while cooking to raise the pH a tad.  Potash works too. The carbonate acts like a pH buffer.  Any excess settles or evaporates out. 

I also do not mix other metals (lakes) with iron except calcium which is benign. Manganese seems safe too. I forget which is the devil with iron: copper or tin. Organic pigments are safe. Nitrates from nitric acid are ticking time bombs. 

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this is going far from the original question but it is getting interesting anyway!
 I believe that a good spirit varnish is totally acceptable on a violin even today but, if I chose to buy varnish, I would go for oil varnish. Anyway, it seems wise to me to choose a varnish that will develop a nice, good-looking patina over the years. That's the main reason why I decided to try oil varnish and this was the advice some older makers gave to me. A hard oil varnish looks a nonsense to me and I would fear that it does not age well.

I remember discussing this with Gio Batta Morassi years ago, and he had an anecdote about a maker who brought a varnished violin top to a meeting, he showed everyone that the varnish was so tough and he couldn't scratch it, even by rubbing it hard against the bench. This varnish would have obviously turned an instrument sound dead. After some time I started experimenting with Fulton varnishes and I made some terpene resin, but I decided to use natural pine resin instead, and I still have a jar of untreated Fulton resin that is now more than ten years old. But, if I remember well, Fulton wrote that a freshly made resin is necessary in order to prepare the red colors.

I wonder if this old terpene resin can be simply heated (with precautions) and turned into a coloring matter for varnish. Would it turn dark brown or greenish brown perhaps? It would be useful if it gave a transparent, warm dark brown.

 

 

 


 

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14 hours ago, David Burgess said:

Either an oil varnish or spirit varnish can sound and age well. Having used both, I wouldn't suggest going all crazy about selecting one or the other.

I agree. Lots of ways to varnish a violin and many formulations which are useful in some context. While my  experience with Fulton turpentine based varnish was that it was harder than I wanted I did have some success using it as a protective isolating layer under softer varnishes.

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On 6/15/2019 at 1:59 AM, ctanzio said:

...

 Many oil varnishes require light sanding between coats to avoid peeling, but makes them susceptible to a phenomenon called "ghosting" if one sands to aggressively. 

...

May I ask what is  "ghosting" phenomenon?  

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1 hour ago, Kae said:

May I ask what is  "ghosting" phenomenon?  

When you sand through the upper most layer of varnish in some places, not in others, and you get a hazy line where you have gone through.

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On the issue of iron darkening varnish, here is an excerpt from Michelman p, 46.

"It was discovered early in this investigation that if iron rosinate is substituted entirely for aluminum rosinate in the sub-varnish (Preparation No. 3), then the varnish film darkens considerably when exposed to sunlight or over a prolonged period of time. The varnish film first becomes light brown, then darker brown, and finally deep brown. A violin was finished with a varnish in which iron rosinate was substituted entirely for the aluminum rosinate; but the varnish became so dark after six months that it was no longer possible to discern the grain of the wood. This varnish spread on a glass plate was brown by transmitted light, but almost black by reflected light."

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On 8/30/2019 at 4:38 PM, Kae said:

May I ask what is  "ghosting" phenomenon?  

 

On 8/30/2019 at 5:40 PM, duane88 said:

When you sand through the upper most layer of varnish in some places, not in others, and you get a hazy line where you have gone through.

"Ghosting" is another term for "witness lines" that demarcate layers of oil varnish. 

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