Official Luthiers Forum!

For sure, a great thread(good eough that it made me sign back up... <g>)

  I thought that it was worth taking a moment to let those who had read

it know that this should never occur when you sand a top and should

never be an issue.

Actually, this has been done for centuries, and still today, on purpose, on  violins. It won't occur if you don't want it to, as in your case, but it can if you wish it to. Simply use a softer backing for your abrasive and go to at least 320. There are many ways to go about anything. Another example: I have freaked out a cabinet making buddy when he dropped by one day; after I had finished fine sanding the entire guitar to 320, I took a hard block with fresh 80 grit paper on it, and ran it with the grain, on the top, and without touching it('cept for blowing the dust off) shot a sealer coat of shellac. He lost it! He thought I was pulling his leg, and would go back and re-do all of this when he left(I did it while he was there because i wanted to finish up and leave), but that -is- how i do -some- tops. If the top has no nothing going for it when sanded smooth(no silk, dead-even color, etc...{you know, wallpaper grade}), doing the above allows light to play in the sanding marks, and adds interest. No, you can't see the sanding marks(if you do this correctly), but the roughed surface is much, much more interesting when struck by light.

Lotsa ways to skin the kitty...

Mario facets his tops!

I shoot an isolator (currently McFadden's Rosewood Sealer) over anything and everything before I shoot poly; I shoot on one mist coat so as not to lift my press-on decals or dissolve and lift stain, and then shoot a decent coat over that several hours later. I do this over Waterlox, over West Epoxy, over stain, over whatever. Oils from rosewood or cedar play havoc with curing polyester, and I just don't want to chance it with anything else, so I use it as my universal sealer. So do some of the big boys like Bob Taylor.

facets his tops!


Hah! There's a name to the technique? Well.... another feature to up-charge for <bg>

Say, Waterlox is rare as, well, rare, up here. As-in, forget finding it.. So, I found some tung oil early this week, and took home a little can and wiped-on a few coats on some random scraps to test with. Stuff won't dry on Cocobolo. Does Waterlox dry on Coco, or dos it remain somewhat gummy???

Waterlox does dry, though slower.

I'm now experimenting with West Systems epoxy pore fill...well, I'm beyond just experimenting and doing it. I just did some ukes that will wind up thusly:
Waterlox, one coat
West Systems epoxy, brushed on, credit card squeegeed off
Sand to wood surface
Waterlox
Rosewood sealer, two coats...that's where I am tonight
3 coats polyester
Sand and then satin urethane or gloss rubout depending on the order

I'll give the tung more time and see where it goes... maybe some japan drier is called-for.

Why the Waterlox under the epoxy? Epoxy "wets" wood like crazy, so it seems like the Waterlox would be redundant?

 Some folks use the polyester as the pore fill, and top coat with nitro, yet you're still using another pore filler? That it fills pores so nicely is another reason to love it, for me. So.... Why the epoxy? Are you trying to minimize  spray booth time, even if it takes a bit more bench time? Just seems, well, unnecessary, but I'm sure you found a reason(that I'm not seeing).

Mario, I'm working through the Waterlox or not Waterlox with the epoxy. I agree that it does not seem necessary, and the McFadden roswood sealer does seem to wet the wood identically to the epoxy.   Yes, I'm epoxy pore filling to try to reduce spray booth time and the total number of coats of polyester from six down to three or four (thin) on natural gloss jobs.   I still think I need the Waterlox on my stain bursts to lock in the metal acid dye.   So I'm really working through to two or three different finish/spray schedules depending on whether I'm going natural or stained, gloss or satin on the different parts. Right now it looks like necks may not need the pore fill...there's something about the contour that accepts coats of polyester differently than flat surfaces. So it's really about how I deal with backs, sides, and tops...and then it also depends on the woods used.

How bout some thanks to the guy who started the thread???

Hello Grumpy,
I'm very interested in getting into polyester (I saw Rick's at Healdsburg and saw the look I like with it). I was wondering - how do you use poly as a pore filler? Do you spray it? If you do, how do you get it into the pores?

Appreciate the help.
Glen

Can you guys tell us more about using polyester as the pore fill? Is this just a matter of spraying it on and letting it flow into the pores... no separate pore filling step?

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

Simultaneous post with Glen, there...

_________________
Todd Rose
Ithaca, NY

https://www.dreamingrosesecobnb.com/todds-art-music

https://www.facebook.com/ToddRoseGuitars/

This thread to me has become a watershed event on the OLF. In all the years I've been reading and posting here and elsewhere, this is THE most informative body of information I've ever seen. Why?...because the pros with experience have weighed in with their comments AND questions. To me it was an example of how serious and unselfish discussions based on experience and facts always advance the state of the art.

And while I personally will never be equipped to spray the Poly finishes it's the mechanics and spirit of the way the discussion has evolved that has impressed me so much. It showed how serious experts put aside their biases and emotions and both ask and answer questions in a respectful and factual manner. Many thanks to Rick, Mario and Kevin in particular on this for the treasure that they give back to this craft.

We're lucky to have more than one maestro in our midst!   

_________________
JJ
Napa, CA
http://www.DonohueGuitars.com

Heh, I'm not interested in Poly, nitro or whatever, I'm a dedicated French polisher with no booth or buffer, but I have found this thread fascinating as well.

To me knowledge is an end in itself, and my knowledge base has been enhanced by Mario, Kevin, Rick etc, so yes thanks to all who have participated great stuff.

Colin

_________________
I don't believe in anything, I simply make use of a set of reasonable working hypotheses.

For pore-filling, just shoot more coats. The stuff is like, 90% solids... Surprisingly, thinning it further than necessary when spraying fills pores better(perhaps allows it to flow -into- the pores).

On all but the largest pores, 4 coats total usually is enough, though I'm  cutting-through quite often(necessitating 2 more coats). I guess 5-6 total would be ideal on those. 3 coats on tops, with a 4th going around the outer edge for safety..

I've also noticed that necks 'fill' faster. 4 coats and done, there, often looking like it was a filled surface. That's where  got the notion to thin further to let it flow -into- the pores better on flat surfaces.

Is there any way this thread can be added to the tutorial page? I'm not ready to do any more spraying at the moment, but I can assure you that I will be hunting this thread up later on for reference and supplier info.

 Is there any difference in buffing between poly and nitro? Is it even necessary to buff out the poly?

_________________
Reguards,

Ken H

great thread. this is way it was when i first started, which is pretty much at the beginning and these kind of talks and lessons were the norm. love it.

from what i have been exposed to not much difference in buffing. may not buff through as easy as nitro, but need to keep watch and do it with some caution as would. can buff sooner and get out the door. only thing i noted, was of course immediate gas off stinks in one of finishes, and we didn't take them into assembly room to do that until end of day. think of bad perm smell. Next day nothing and buffed out. same wheels, compounds etc that i am aware of

One way to use poly as a pore filler (this thanks to Bob Taylor) is to shoot rosewood sealer, then the next day brush on and squeegee off a coat of full strength polyester. Wait overnight, and sand back to flat wood or nearly so. Shoot one more coat of rosewood sealer to get the isolation and to wet the wood equally. Wait 24 hours. Scuff and shoot three to four topcoats of polyester.

BTW, I thin the polyester 23% to 25% with MEK. I've tried acetone and also butyl acetate as thinners, and the MEK helps bond coats and flow out better than anything else.

DO NOT CONFUSE MEK WITH MEKP!

My current thought for most natural finish instruments is epoxy pore fill, sand, two coats rosewood sealer, scuff, three coats of polyester, cure, sand, buff.   That gets it to a two or three day finish schedule, then a two day cure would be nice.   So you can to a finish in a week. For four of the instruments I brought to Healdsburg, I compressed that into three days total. I started the finish process on Monday and set the instruments up on Thursday and brought them to the show on Friday morning. They looked fine and they still do. So really you can do a complete finish in three days from white wood start to final buff out.

Bear in mind that this is without going to the expense or hassle of UV cure.   So why go to UV cure unless a three day finish is too slow?

BTW, I'm writing all of this up and taking pictures for a Guitar Maker Magazine article. I'll have all the product numbers, etc., etc. for everything from chemicals to paint to stains to sand paper.

Rick, you are the man. I have a feeling this particular issue is going to sell very well.   

OK, question to either you, or Grumpy, or Mr. Gallagher: for a one-man shop, this stuff is sprayed with a typical HVLP type set up? Anything special to the hardware?

Thanks again.

Bill

_________________
Eagles may soar, but weasels don't get sucked into jet engines.

Too cool i can't wait

I hope you go into Personal protective equipmnt as well.

Rick,

Do you know when the article will be coming out?

Let me finish the article first!

Yes, full protective gear and a "real" spray booth for me.

HVLP Sata NR-95 gravity feed gun modified with the 3 M PPP system for quick change and disposable cup liners.

The next thing I want to design is a good cleaning solvent recycling system where I can spray acetone through the gun and instead of blowing it into my overspray filters, it would trap the atomized acetone and collect/condense it back to liquid on a set of metal louvers.   I think the catalyzed material would sink to the bottom of a bucket and we could reuse the reclaimed acetone for cleaning.

I'm not sure if I missed it in this voluminous thread,
but -What is "rosewood sealer"?
Thanks,
Brad

McFadden's Rosewood Sealer