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PostPosted: Sun Dec 16, 2007 4:20 am 
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Cocobolo
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Has anyone used shellac as a sealer under spirit varnish? I have a violin kit
that I am assembling (last 3 guitars and the current Tele awaiting buffing
were all built from scratch...well the wood parts anyway I am finish
sanding the violin and about to start finishing. This consists of a light
staining then a sealer prior to varnish schedule. Will good ole shellac work
as a sealer under the spirit varnish? Any advise will be appreciated.

Thanks K


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PostPosted: Sun Dec 16, 2007 4:38 am 
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Contributing Member
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A lot of mandolin builders use shellac as the sealer under varnish. Try to find the DIY TV info from "Handmade Music" where Lyn Dudenbostal builds a mando. Killer looking too!

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PostPosted: Sun Dec 16, 2007 4:55 am 
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Koa
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shellac works well as a sealer under many finish including varnish, polyurathane and lacquer. You should use the dewaxed shellac as the sealer under waterbased finishes and polys. Dosent work well under some new epoxy type finishes.

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PostPosted: Sun Dec 16, 2007 5:10 am 
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Koa
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test on scrap! I built myself a violin, and applied a quicky shellac spit coat so's not to dirty it while playing it "in the white". When it turned out to be fine as it was, I disassembled it and began varnishing. It all crackled!

I have yet to strip and re-finish it, it was so disheartening.

Some varnishes go well over shellac, some don't. Test! Always test... Wish I'd have followed my own advice that time <bg>



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PostPosted: Sun Dec 16, 2007 6:29 am 
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Brazilian Rosewood
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Grumpy's advice is good for any finish- or finish combo.

Most spirit varnishes are quite different from the oil-based finishes (Rockhard, etc) that most folks think of as 'varnish'.
In fact, some guitar builders apply spirit varnish mixtures using French Polish techniques- simply calling it French Polish- while others use straight shellac for FP.

So, you will probably be OK with the shellac under spirit varnish, but test first.

Cheers
John


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PostPosted: Sun Dec 16, 2007 9:12 am 
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Cocobolo
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If not will a coat of clear varnish work as well for a "sealer" coat prior to color
or does it amalgamate. Sorry if this is a silly question, I'm just not well
versed in the varnish world.

Thanks, K


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PostPosted: Sun Dec 16, 2007 11:30 am 
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Koa
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I would thin it first with paint thinner or turpentine. Here is a link to site that deals with violins and the likes. They have a forum. I havent joined yet but you might be able to find more info on violins there then here. I have an interest in violins too and own a few old ones but i'm new to the violins too so i'm not one to give you expert advice. Good luck Mike
Maestronet

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PostPosted: Sun Dec 16, 2007 1:11 pm 
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Cocobolo
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Kahle, there are many different ways to seal the violin. Diluted varnish will work. So will thinned shellac, gelatin is also a good sealer. Knox brand from the grocery store will make a nice sealer before you apply a light stain to help even out the stain in the end grain areas.

BIG SUBJECT


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PostPosted: Sun Dec 16, 2007 7:57 pm 
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Brazilian Rosewood
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Traditional sealer is egg white.

Colin

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PostPosted: Mon Dec 17, 2007 3:44 am 
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Brazilian Rosewood
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Spirit varnish should be thinned with alcohol, not paint thinner or turp.


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PostPosted: Mon Dec 17, 2007 6:03 am 
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Brazilian Rosewood
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In essence, shellac _is_ a spirit varnish, and a lot of violin varnishes do contain some shellac. It should be perfectly compatable, althogh it never hurts to do a test piece or two.

I'd bet Mario used an oil based varnish, and it either didn't stick properly to the shellac, or it was harder. The old painters rule, 'fat over lean', says that you should use more oil and less resin in the medium as you build up, so that the surface layers are more flexible than the ones underneath. When the base wants to move, and the surface doesn't, you get crackle. That's the basis of all of these 'antiquing' methods. In theory an oil varnish over shellac should follow the rule, but some modern oil varnishes get pretty hard.

One problem with using shellac as a sealer under oil varnish is that frequently the index of refraction is different. This can give a 'cloudy' or 'veiled' look to the finish. It can be especially problematic if you seal with shellac, build up some oil varnish, sand through when leveling, and then put on more varnish. The finish will look spotty. Ask me how I know.....

No, don't.

You do need to use some sort of clear sealer under colored violin varnish, though. If the color soaks into the end grain the result is a dark and muddy spot. Again, the voice of experience.....

Various makers use different sorts of sealer coats and ground coats on violins, and discussing them is a great way to start a fight at any meeting of violin makers. Within about five minutes they will be breaking chairs over each others heads. A simple one to start out with would be a very thin layer of the same sort of varnish you're going to finish with, but thinned out and with no color in it. Wipe it on with a rag or pad, and get it as thin as you can. If it looks 'dry' on the end grain or on parts of the curl, put on another coat or two. Once it's dry _touch_ the surface with the finest sandpaper you have, just to make sure there are no runs or dust, and then start brushing on the colored varnish. The thinned out clear varnish should have filled the pores in the end grain and will stop the penetration of the color. Since the IR is the same, the result should look nice and clear and 'deep', and the thin coats won't soak in very deeply before they harden, so you avoid too much build up.      


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PostPosted: Mon Dec 17, 2007 7:33 am 
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Koa
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[QUOTE=Colin S] Traditional sealer is egg white.

Colin[/QUOTE]
I have heard this before. I have also heard of using ground eggshells mixed in a way like using pumice to fill grain on french polishing. has anyone else ever heard this? Don't know if the old guy that told me this years ago was pulling my leg or what.

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PostPosted: Mon Dec 17, 2007 7:41 am 
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Koa
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I'd bet Mario used an oil based varnish

You betcha! But it was just a spit coat of shellac. Mostly alcohol, so I didn't expect an issue in the least.

The warning stands. test!

Good info on the thin-thin coats first. I didn't know that "trick", but it makes sense.

Violin makers have their varnish to fight over, mandolin makers bicker endlessly over glue, and guitar makers have CNC as the taboo subject. Someday, I hope to CNC a complete guitar, take it to a mandolin maker to glue it with Titebond, then ask a violin maker to finish it in polyester. That oughta be good for beginning  WWIII



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 Post subject:
PostPosted: Mon Dec 17, 2007 7:42 am 
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Old Growth Brazilian
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I have used egg white as a pore filler before, but I have never heard of using ground egg shell as an abrasive as in a pumice like fill. The problem I see is the shell will deposit in the pores along with the wood fibers it scrapes off just as pumice does. However pumice will go to near clear as it absorbs the shellac and solvent. I really doubt egg shell grinds will. Also FFFF pumice is pretty fine stuff. I doubt you grind egg shell anywhere near as fine in a coffee grinder anyway.


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 Post subject:
PostPosted: Mon Dec 17, 2007 2:41 pm 
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Koa
Koa

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"Someday, I hope to CNC a complete guitar, take it to a mandolin maker to glue it with Titebond, then ask a violin maker to finish it in polyester. That oughta be good for beginning  WWIII "


   


if only it wernt true!



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 Post subject:
PostPosted: Mon Dec 17, 2007 4:46 pm 
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Cocobolo
Cocobolo

Joined: Wed Dec 13, 2006 9:41 am
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Location: United States
Tested the clear varnish over shellac. No bubbles, cracks, or other
associated nastiness thus far (test sample was applied this morning, Mario,
was your reaction immediate or was it like a time delayed grenade type
thing?) If all is well with it tomorrow... On with the show!!

Ken I am curious about the gelatin sealer. Knox gelatin is essentially hide
glue. Would an application of perhaps thin hide glue act as a sealer? That
would certainly make me less maniacal about cleaning every last bit of
squeeze out if that is indeed the case.


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 Post subject:
PostPosted: Tue Dec 18, 2007 2:55 pm 
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Koa
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gelatin will work as a glue but it strength is no where comparable to hide glue. But then your not looking for strength. Gelatin is produced by the rendering of bones and cartilage. Hide is made from the rendering of hides and hoofs. much more colagen rich then just bone and cartilage. Wood workers have used glues as seal coats for years. They call it glue size. Its used to seal end grains and various woods to prevent improper glue joints like gluing two end grain pieces and for sealing woods to prevent splotchy stain jobs in woods like pine and in end grains of other woods. You could thin the hide glue by about 50% or use white glue thined with warm water again with 50% water. brush it on let dry then sand down.

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PostPosted: Tue Dec 18, 2007 6:59 pm 
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Cocobolo
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Link

Check out above link.


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