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Vernice Bianca using liquid Gum Arabic watercolor solution?


Joe Swenson
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Hi All,

I am ready to finish my first violin and was opting to go with the Sacconi Recipe for Vernice Bianca ground:

25g of gum arabic,

1/2 teaspoon of honey,

1/4 teaspoon of rock candy,

about 100cc of water,

albumen from one egg white.

I went to the local art supply and they only had gum arabic in the liquid form. Windsor & Newton Water Color Gum Arabic. 75 ml bottle. I am assuming this is more concentracted than I would want to use for a ground coat on a white violin.

Does anyone have experience with this form of gum arabic and a sense for how much to dilute this for the ground coat. My gut says I should double the water volume to make 150 ml of Vernice Bianca. But that's just my guess. The starting consistency of the gum arabic solution is like thin hide glue. But not like plain water.

After reading a previous post about someones experience applying gum arabic too thickly and that it remaind tacky, and the respondant stating how it should soak into the wood and not be visible when it dries, I am thinking if its too thin I can always apply a second coat if needed.

And I planned on coating the inside as well as outside with the ground coat. Seems like sealing the wood inside and out makes the most sense.

Thanks!

Joe

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Difficult one if your trying to be exact,as solutions of gum arabic can be anywhere up to 55 % strength,but they are very thick.I think the general artist stuff for watercolours is around 20 %. (14 degree baume is mentioned by some but i dont know about baumes :) )If i were you i would use the whole bottle and only use 25cc of water. If the whole solution when mixed is too thick .Add a bit more water to make a thin solution.

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For the egg white you must beat it to a stiff foam and leave to stand in a sieve. collect the liquid that drips from this called glair. Your gum arabic solution needs to be the same consistency as the glair ie rather dilute. Measure the consistency by feeling the liquid between your finger tips. I'd not use the sugar and honey personally. This is a sealer. Ideally it will seal the wood but once applied and dry it is not visible.

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Any thoughts on the advantages/disadvantages of a water soluble ground, on something which will be exposed to perspiration?

Good point.

I wouldn't advise the use of something like this as a ground in itself. AS weak size it can be useful for part sealing the wood to control the penetration of something that IS more waterproof and more suitable to form the body of a ground.

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Thanks for the link on the old post! I did a search but didn't come up with that one.

Yes this gum arabic solution is fairly thin already so I'm thinking adding the 25 ml of water to make 100 ml is what I'll try.

The back of the bottle lists "Gum Arabic, preservatives, water" as the ingredients.

If the gum arabic plus egg albumin is to seal and provide adhesion for the first varnish layer, plus it being hydroscopic, would it be better not to put it on the inside of the instrument? I read a coat of very thin hide glue also works well as a sealer ground coat. And since no varnish goes on the inside wouldn't that work better in that area?

Is there any wisdom on using ground inside the instrument?

Thanks so much for the advise!

Cheers,

Joe

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Any thoughts on the advantages/disadvantages of a water soluble ground, on something which will be exposed to perspiration?

Certainly outside of instrument making, the use of water based colors and grounds under varnish is well established. Apparently this was still the normal structure for paintings in Andrea Amati's time.

As evidence of its continued and broader use, Watin and others describe Chipolin as kind of royal wall finishing. Chipolin was basically a carefully applied white mineral ground in water based glue, followed by varnishing. Well executed Chipolin was reputedly an extremely durable material, once dried.

None of this necessarily means anything for instrument making. Except that we shouldn't easily dismiss the plausibility of water binders under varnish.

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I thought my post from this morning would go through... SO apologies for repeating my question.

So would that glue be hide glue? That was one of the grounds I read people had used.

And so I was wondering if that were an appropriate ground / sealer for inside the instrument where no varnish would be added.

Is sealing inside a common practice?

Part of the function of the ground is to harden the wood a bit, correct? I felt like the spruce top i am using is faily "soft" between the grain lines...

Cheers,

Joe

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Wouldn't a water-soluble ground be protected from excess moisture by the overlying varnish?

The varnish will protect against liquid water but water vapor won't be stopped anywhere near as well. Since a violin is played underneath a person's face water vapor could be an issue.

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..............

Like we see on old Cremoese..... :)

It's something I've wondered about. Old writing has described Strad varnish as chippy. I've never noticed this, so maybe that description came from the appearance, with abrupt edges, as if it had chipped away? There have also been descriptions of a poor bond between the varnish and the ground, which I've never noticed either. Perhaps that description also was based on the appearance of existing wear, rather than from actually banging the instruments around to see what happened?

What if there was a layer in there somewhere which softened or dissolved with moisture? That might allow pieces to be pulled away, leaving the abrupt edges, even if the varnish was pliable, and not hard and chippy.

I did a few experiments with this on samples, applying a sealer, then a water soluble coating. Part of this was masked, and then varnish applied to the rest. With the masking tape removed, a wet paper towel was left in place for a while, with the idea that moisture might make its way under the edge of the varnish where the masking tape had been, and travel a ways through the water soluble layer.

Interesting results, though not as dramatic as I expected. More experiments could be done.

If this happened at one time, why doesn't it seem to happen today?

Who knows? Maybe susceptibility to moisture has been altered by the application of various polishes and oils over the years, or maybe the vulnerable layer finally changed state into something less vulnerable. I've read that egg white will eventually do that, but don't really know.

Just some thoughts.

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I also thought I understood that it hardens the wood which helps the tone.

I also thought leaving the bare wood exposed would allow moisture to penetrate the wood on one side and cause uneven stresses.

I have a sheet of plywood I varnished on one side and left the other side bare. The bare side is expanded now and the sheet is quite "curved" the varnish side did not absorb moisture and expand. It would seem that leaving the bare wood would precipitate warping and cracking down the road. Is this not true?

If so it seems to make sense to seal the wood inside and out. That is, unless of course there are things still in the wood that over time need to "come out"... as part of the aging process? And I can see that sealing would certainly prevent that process.

I am certainly a beginner at this, but a scientist by training so I have to ask these questions. :D

Thanks,

Joe

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I wouldn't bother. The ground doesn't do much except to help prepare the wood for varnishing. Bare wood on the inside does just fine.

My experience is very limited - just finishing number 6 - but I have always used the sealer inside. I have no idea if it makes any difference and have no way of telling. The only thing I can say is that I don't think if does any harm...

Does Sacconi mention it?

Regards,

Tim

(Now over the acronymitis.)

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Varnishes and sealers are only good at stopping liquid water from reaching the wood (the waterproof ones at least) but they're not good water vapor barriers. The only reason I can think of for putting a sealer on the inside of a violin is to slow down moisture changes in the wood but sealing the inside won't help much with that. One potential problem with putting sealers on the inside is that if they are too smooth they can make the soundpost want to pop out of place.

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Apparently Google is the est way to search this Forum. :lol:

I found this post from 2004:

http://www.maestronet.com/forum/index.php?showtopic=251479

... Jacob once mentioned taking a Chinese fiddle and covering the f-holes, pouring vernice bianca down the endpin hole and sloshing it around to coat the inside, and pouring out the rest. After it dried he said its tone was better.

And many other's commented they do coat the inside, some with propolis, most with Vernice Bianca.

So far no evidence for using thinned hide glue.

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Does Sacconi mention it?

Apparently so: from a posting in the WoodWorkersZone forum (which is where I got the recipe in the first place)

http://woodworkerszone.com/igits/showthread.php?t=7299

"...It is used as a ground before varnish is applied. Sacconi believed that Stratavari also used vernice bianca on the innards of his fiddles too. Simone Sacconi has a book called Segreti di Stradivari or Secrets of Stradivari. You may already have it, if not you may be able get it at your local library. It's quite expensive to buy. Anyway, he talks about vernice bianca in his book."

Cheers,

Joe

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Just finished coating (twice) the instrument front and back and neck inside and out... I'm leaving the sides until I get the top glued back on and I get any glue drips cleaned off the ribs first. I think the solution was a tad watery, as it made the wood look wet. And soaked in the maple back in spots where the grain was more exposed. The gum arabic solution seemed a bit thicker than I originally thought so I doubled the water volume to 150 ml.

I also probably needed to let the meringue sit a bit longer as I ended up using only about 1/2 the volume of the albumen that was produced. But I started with 75 ml of liquid (1/2 the total gum arabic + honey + sugar) and it was a jumbo egg. Might be nice to know the ml of albumen that is recommended for this recipe. Maybe eggs were smaller then?

The second coat on the spruce top seemed to sit on top much better indicating the first coat did seal. Wasn't sure how long to let the first coat dry. Letting it dry overnight. Hoping I didn't get things too wet. Top looks pretty good. Started out a 66 gm, after 2 coats it was up to 80 gm. We'll see what it wieghs in the AM.

Cheers,

Joe

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This morning it was all pretty much dry with a fairly rough feeling surface. Tonight Weight is back down to 70 gm after drying for 24 hours. So I think the process worked pretty well.

It definitely makes the top "crispier" sounding and more rigid when handling under your fingers. Going to measure the tap tones tonight again to see how they changed with the ground coating. Then I'll glue on the top.

Two questions:

Wondering if there is a ml amount of egg albumen to add to the 100 ml of gum arabic solution. I used a jumbo egg and only used part of the total albumen produced since I didn't wait long enough until it all had settled out.

AND Labels... can they go in through the sound hole after the fact or should I wait to glue on the top and make my label tonight?

Cheers,

Joe

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