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PostPosted: Thu Jul 18, 2019 12:41 am 
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Mahogany
Mahogany

Joined: Tue Jan 15, 2013 10:00 pm
Posts: 68
First name: Josh
Focus: Build
Status: Amateur
My favourite finishes for acoustic guitars are wiping varishes; tru-oil is great, although I prefer Liberon Finishing Oil and even some wiping polys. Thin, beautiful protection for the instrument, with a hand-rubbed look, lightly buffed out to a smooth satin. Necks feel incredible. Don't even need to porefill. It feels relatively safe to use. Relatively quick process. If I was only building guitars for myself, I'd never use anything else.

However, most people who are interested in paying me for a guitar want high-gloss. So it's back to the spray rig, and epoxy pore filler and buffing machine and a can of Mohawk and I give 'em what they want. Spray outside, wearing a respirator. Luckily I live in a warm climate so I can spray year-round. I swear I can feel the nitro fumes melting my brain cells during off-gas. Instant headache.

As Alan says, there's no perfect option. Except maybe anti-gloss reeducation camps for the guitar-buying public.


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PostPosted: Thu Jul 18, 2019 1:18 am 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Sun Mar 30, 2008 8:20 am
Posts: 3530
" I swear I can feel the nitro fumes melting my brain cells during off-gas. Instant headache. "

I used to get a headache from the fumes, but over the years that quit happening. You might want to find a different place to let things off gas and save a few brain cells.


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PostPosted: Thu Jul 18, 2019 9:09 am 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Fri Aug 19, 2005 4:02 am
Posts: 2110
Location: The Woodlands, Texas
First name: Barry
Last Name: Daniels
I installed a low-powered bathroom vent unit in my spray booth that runs for a week or two during the off-gassing. No more fumes in the house. Makes my wife happy.



These users thanked the author Barry Daniels for the post: Joe Beaver (Sun Jul 21, 2019 12:36 pm)
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PostPosted: Thu Jul 18, 2019 1:21 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Sat Jan 15, 2005 12:50 pm
Posts: 3303
Location: United States
I've been using the Murdoch's 'Ure-alkyd 500' floor varnish made by Sutherland-Welles in Vermont since they stopped making the original Behlen's 'Rock Hard Table Top ' varnish a few years ago. The Murdoch's is actually significantly harder, and also much clearer and lighter in color. I'm told that make the resin from the waste from the Cabot cheese factory, and they use citrus solvent rather than mineral spirit for the vehicle, so it smells nicer. It's slower drying than the Rock Hard. UV light seems to speed that up usefully, and the sooner you get it under the lights after putting it on the better.

The major issue I've had with the Murdoch's is that it dries slowly, or even fails to dry, on some woods. It's not simply the ones that are particuilarly oily: so ar it seems to be OK on Brazilian rosewood, for example, but Indian rosewood, Morado, and Macassar ebony have been more problematic. A puzzling thing is that it works on some pieces of those woods and not on others. Sealing with shellac didn't seem to help; CA works better for that. These days I do finish tests on off cuts of every set of wood, and avoid using problematic ones for things like binding.

I've always brushed varnish. I like a small, soft 'camel hair' type of brush. Get a good one, but don't go overboard with badger or whatever. I would guess this stuff is thin enough to spray out of the can. I've never gotten into the thinning schedule that I used with the 'Rock Hard', using reducer and acetone. It brushes on thin, and shrinks down as it cures, so even using 8-10 coats with very light scuff sanding between with #400 results in a finish coat only .003"-.005" thick, and usually on the thinner side, so far as I can measure.

A somewhat softer varnish that has had a good rep in the lutherie world is Pratt & Lambert's #38. I actually ran some tests with it when I was going to stop using Rock Hard, but heard the P&L had gotten bought out by Sherwin Williams. THey seem to have retained the P&L name and line, though, if that's the case. THe #38 seems to be quite comparable to the old 'Rock Hard', but not as hard as the Murdoch's.



These users thanked the author Alan Carruth for the post: Joe Beaver (Thu Jul 18, 2019 3:31 pm)
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PostPosted: Thu Jul 18, 2019 3:13 pm 
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Contributing Member
Contributing Member
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Joined: Thu Feb 09, 2006 2:35 pm
Posts: 2823
Location: United States
First name: Joe
Last Name: Beaver
City: Lake Forest
State: California
Focus: Build
Alan, That is an interesting product. I was wondering if you fill the pores with anything other than their Hard Sealer? If you do use it how many coats for a rosewood? Sand back with each coat?

_________________
Joe Beaver
Maker of Sawdust


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PostPosted: Thu Jul 18, 2019 7:09 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Wed Feb 20, 2008 7:15 pm
Posts: 5683
First name: Ed
Last Name: Bond
City: Vancouver
Country: Canada
Focus: Build
Status: Professional
Thanks Alan...


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PostPosted: Fri Jul 19, 2019 11:53 am 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Sat Jan 15, 2005 12:50 pm
Posts: 3303
Location: United States
I've used various pore fillers. Probably the best one is the pumice/shellac fill that's used when French polishing. It's labor intensive, but quite durable. The traditional silex/oil filler is a mess, shrinks a lot, and is slow to dry, but other than that... CA works well enough, if you can stand the fumes. I'm not a big fan of epoxy, since it's so allergenic/sensitizing. It's also a pain to sand back, as is CA fill. I've used a couple of transparent fillers that worked OK, and even used latex wood filler tinted with various dyes and pigments. As with finishes, there are lots of ways to do it, and all of them have drawbacks. Yuo pick the one that has the features you need and drawbacks you can live with.



These users thanked the author Alan Carruth for the post: Joe Beaver (Sun Jul 21, 2019 12:38 pm)
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PostPosted: Fri Jul 19, 2019 12:31 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Fri Aug 19, 2005 4:02 am
Posts: 2110
Location: The Woodlands, Texas
First name: Barry
Last Name: Daniels
I have tried lots of new stuff over the years and keep going back to oil based silex filler and nitro. It just works.


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PostPosted: Sat Jul 20, 2019 7:38 pm 
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Brazilian Rosewood
Brazilian Rosewood

Joined: Sat Jan 15, 2005 12:50 pm
Posts: 3303
Location: United States
That's why the factories use it: it works, for now....


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