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Damar Varnish Question
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rs
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PostPosted: Sat Jul 18, 2015 6:53 pm    Post subject: Damar Varnish Question Reply with quote

I have a question about the damar varnish I have made. When I heated it (cracked it really)and cooked it into oil, the result was dirty looking. I have tried instead heating stand oil and adding damar to the hot oil (not smoking but about 200 degrees or so). The damar dissolves in the oil. I use just enough stand oil to dissolve the damar. It ends short oil, that is, more damar, less stand oil. I tried walnut oil, but it gets the burnt flecks when I use it instead of stand oil. After the stand oil/damar varnish cools, I then have a paste that I mix into room temperature walnut/alkyd oil. The ratio is about 50/50 damar paste/walnut oil. That's my varnish.

I love the appearance of the varnish and it is very soft. It works easily and dries in the sun in two days. It wears quickly but doesn't chip, yet anyway. It is very transparent. I have made two instruments with this varnish and although pleased with the results, I wonder: In the future will the varnish cause me problems? I would hate to make the next thirty instruments with it only to find after five years it starts to disintegrate, or worse, to peel. Any suggestions or am I worrying too much?
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DonLeister
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PostPosted: Sat Jul 18, 2015 11:26 pm    Post subject: Reply with quote

What is your walnut /alkyd oil?
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rs
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PostPosted: Sun Jul 19, 2015 7:10 am    Post subject: Reply with quote

The walnut/alkyd oil is M. Graham Artists' Medium:
http://www.amazon.com/M-Graham-8-Ounce-Walnut-Medium/dp/B0006OJAIS/ref=sr_1_1?ie=UTF8&qid=1437303955&sr

I bought it at an art supplies store. The stand oil is Winsor Newton.
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DonLeister
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PostPosted: Sun Jul 19, 2015 10:01 am    Post subject: Reply with quote

All I can do is offer an educated guess, it seems like an overall oil-rich varnish which should stick but as for how it ages is hard to predict. Let us know how it works over time.
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Dave Chandler
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PostPosted: Sun Jul 19, 2015 4:46 pm    Post subject: Reply with quote

You say it wears quickly, what evidence do you have? I agree with Don -- It seems if its already mixed with stand oil, then mixed again with walnut oil, its pretty long on the oil.
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L P Reedy
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PostPosted: Sun Jul 19, 2015 6:12 pm    Post subject: Reply with quote

I don't use any of those components, but two days in the sun is a rather long drying time, indicating that it will not be fully cured for several months. I would be more concerned if it were chippy at this stage.

I've never heard of an alkyd oil. The resins I use fit the definition of "alkyd," so it may be that what you have is some mixture of walnut oil and an alkyd resin. If so, you really don't know what you have. When fully cured your varnish may be perfectly fine, but it doesn't sound like anything I would use, simply because I like to know what I have.
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Dave Chandler
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PostPosted: Sun Jul 19, 2015 6:33 pm    Post subject: Reply with quote

To my understanding -- If your damar resin is cooked with the stand oil long enough, they become one, a varnish. If you mix this varnish with walnut oil at room temp, then you're using the walnut oil as an thinner, which will not form a part of the varnish, but will have to evaporate off. Could explain long drying time. Whether the varnish is too brittle, or too soft, will probably have nothing to do with the walnut oil, which would in time have evaporated, but with the original ratios of resin to stand oil.

As an aside, I went to put a fiddle with a final "volatile balsam oil" varnish in the sun, and within a couple minutes, it started to form very large bubbles. I pulled it inside quickly before much damage was done. I think the warm sunshine made some of the components of the varnish form a gas under the final layer.
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Last edited by Dave Chandler on Sun Jul 19, 2015 6:38 pm; edited 1 time in total
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rs
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PostPosted: Sun Jul 19, 2015 6:35 pm    Post subject: Reply with quote

Thank you for the replies. The long oil final product observation you mentioned, Don, gives me a little more confidence.

Dave, I noticed this when I was French polishing the back of my last instrument varnished with the above recipe. It was, in fact, the first one I made with the varnish. I had grabbed the upper bout and grabbed it kind of tightly while going to town on the back. The edge varnish "pushed back" exposing the underlying ground where my left hand had been gripping it for a couple of hours. The edge of the varnish was dark there, also. It looked as if I had started a wear-pattern. I have never had other varnishes do that just from my working it on my end. Regardless, it looked nice to me. I concluded that it would not take long to wear-in a pattern if I could do so through aggressive French polishing; something I have never accomplished with any other varnish by just working on it, albeit aggressively.

The fastest wearing varnish I ever saw, in fact the best varnish I ever used was some Magister Linea Cremonese varnish I used for a violin that I made for a client in Florida. Within a year, a nice pattern was worn in the upper treble. Granted, she plays a lot playing for a local orchestra in St. Pete. Yet, even with that varnish I never had the varnish start to wear while still in my hands.

I am not sure the above softness is a good thing to others to have in a varnish, but it is very appealing to me, as long as it doesn't fail.
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rs
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PostPosted: Sun Jul 19, 2015 6:41 pm    Post subject: Reply with quote

L. P. Two days is about what I usually get, except on straight commercial stuff. So that sounds ok to me. Your curing time raises a concern for me to think about, however.

"In the multitude of counselors there is accomplishment" Proverbs 15:22
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Dave Chandler
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PostPosted: Sun Jul 19, 2015 6:54 pm    Post subject: Reply with quote

RS, I've done "french polishing" with spirit varnishes, so I'm curious how you french polish an oil varnish. Are you using alcohol to "spirit off" the oil in your varnish?
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rs
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PostPosted: Sun Jul 19, 2015 7:03 pm    Post subject: Reply with quote

Dave, I had been using shellac and olive oil, although the past few months I have been using Qualasole. It cuts the time in about half for me. I used Qualasole on the instrument I just mentioned.
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DonLeister
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PostPosted: Sun Jul 19, 2015 9:00 pm    Post subject: Reply with quote

Uh, walnut oil is a lot like linseed oil, it isn't going to evaporate. It will polymerize and dry just like linseed oil.
I see what you mean though Dave, walnut oil will thin the consistency of a varnish and help it spread and slow the tack time.

You can 'spirit off' a varnish if it has enough alcohol soluble resins in it. It's similar to french polishing but you are not adding shellac or qualasol , just using alcohol and oil to polish.
A high oil content varnish ( long oil ) won't want to soften and spirit off as well as a varnish that has less oil and more resins, or one with a layer of shellac from previous french polishings.
All of that is going to depend on the particular mixture you have.
Going by the varnishes I have made, the leaner ones definitely soften and polish well with alcohol, my Fulton varnish is so tough alcohol won't do much to it.
Actually, except for the Fulton stuff, alcohol is my first choice if I need to strip an instrument, provided the color is not there and going to go into the wood in a bad way.
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Michael Darnton
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PostPosted: Mon Jul 20, 2015 7:30 am    Post subject: Reply with quote

A few things:

When I started, I used a dammar varnish that I made by cooking the resin quite hot for several hours, until it was reduced to around 1/2 of what I'd started with. It has a lot of waxes in it, and this is simply burning them off; it is a VERY smoky process! Then I added pre-cooked oil 1:1 with the resin, and cooked until I got long strands when touching the cold varnish. I also did the same process without all the initial cooking, but the varnish was quite a bit lighter and less interesting. I added turpentine when the varnish had cooled enough so that it didn't immediately boil off. You can't always add turpentine to thin varnish after it's cooled, but this varnish was very amenable to that, also, so I stored it as a putty-like mix. I still have some from 1991, I think.

This varnish worked very well. It dried a bit slowly, but has proven to be extremely durable. It wasn't very clear for the first few years, but when I see it now, I'm pleased. In the long run it's all good.

Oil varnish goes through many phases, continually, through time. At some points it's very alcohol soluble, at others not so much. At certain points it can turn and start to seriously degrade on its own. This is just the way it is. Some people say you can identify an oil varnish by its insolubility, and this is definitely not true. Painting geeks have identified changes in oil over centuries, and it's one of the ways they date paintings.

You need to use clean, good quality oil. Expensive artists linseed oil is the way to go, since you won't need much of it. Many problems can be traced to using bad oil, so don't skimp on that and don't mess around.
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DonLeister
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PostPosted: Mon Jul 20, 2015 8:08 am    Post subject: Reply with quote

Michael, about your dammar varnish, when you say 'extremely durable' does this wear at all, or does it wear in a nice way? Have you seen any craquelure develope or other texture?
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Michael Darnton
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PostPosted: Mon Jul 20, 2015 8:46 am    Post subject: Reply with quote

None at all.
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