finish bah humbug

pb+j · #1 06-19-2014, 10:08 AM

I'm far from a professional or expert but over the years I've made a few solid body instruments from scratch and refinished many more.

It seems to me that finishes aimed specifically at luthiers are finicky and dangerous or problematic and expensive. I've used pore-o-pac filler, that other behlen filler, shellac, nitro sanding sealer and CA glue as a filler. As a topcoat I've tried Nitro, and acrylic lacquer, and Qualisol, no longer available, and tru oil, now I'm using KMT9 with a shellac undercoat. They all have different serious liabilities.

Years ago I remember a post from Rick Turner where he said he was using "oil modified urethane" meant for floors. He said it was cheap, readily available, and did everything you want in a finish--cured fast, cured hard, leveled well, looked good. Could be applied thin.

Recognizing that it takes time to master the skill of finishing, and it's probably better to stick with a single method and make it work, I think next time I try this I'm going to go with something like that. Something commonly available at Home Depot or the paint store.

Alan Carruth · #2 06-19-2014, 10:29 AM

A friend of mine points out that, when there are a lot of ways to do something, it's a sign either that all of them work, or none of them do. I'm convinced that guitar finishes are a case of 'none'. We're all trying to find the 'perfect' finish when none of them are even 'good' for our use.

Up until they discontinued it, I used the old 'Rock Hard Table Top' varnish from Behlen's. It took me some years to figure out how to deal with all the problems, especially 'witness lines', but I got it to work pretty well. Then they stopped making it (the new formulation is a polyurethane).

When I run out of the Behlen's, I'm planning on moving to 'Murdoch's Ure-Alkyd 500' floor finish from Sutherland-Welles. It's slower drying than the Behlen's, but clearer, and seems almost as hard as nitro while still being flexible. It also seems to have fewer witness line issues. It's expensive, though.

In the end, I think the 'best' finish is the one you can get to work best for you.

Frank Ford · #3 06-19-2014, 10:32 AM

Some time ago, a luthier pal told me that the biggest problem is the name:

It shouldn't be called "finishing."

It SHOULD be called "BEGINNING."

I think that sums up the situation concisely. . .

pb+j · #4 06-19-2014, 10:39 AM

LOL I love both these replies!

So far KTM9 is not working for me. But this is my first time with it. It's a real pain to brush. Its going to take a LOT of sanding and polishing.

What percentage of finish applied ends of being sanded off again?

LouieAtienza · #5 06-19-2014, 10:58 AM

Best stuff I used so far is from Sherwin Williams automotive, called Finish1. It's a 2-part urethane that dries fast and hard and very clear. It's almost a no-brainer to spray, and it levels beautifully and polishes to a deep wet gloss if desired.

I have done quite a bit of on-site brush finishing with oil-based finishes. Using Penetrol can really help an oil finish flow out and level off nicely - so much that I even used it when finishing floors. Might be worth a try...

redir · #6 06-19-2014, 12:11 PM

yup takes me jsut as long to finish a guitar as it does to build one, least it seems that way. I'm almost exclusively French Polish these days. After ten years of trying various water based including KTM I gave up. It's just not consistent enough. I enjoy FP and it's about the most harmless finish there is especially if you get good drinkin' grain alcohol.

I do want to try the hard FP which I thought was called Table Top but maybe I'm thinking of something else.

Quickstep192 · #7 06-19-2014, 12:29 PM

Just to throw another wrench in the works, there's now KTM 10. I like that it is totally clear and seems to impart no bluish cast. In fact it is so clear that I had to tint it with some TransTint dye to amber it up a bit. It wets the surface much like nitro or oil based finishes and gives incredible grain pop and depth. I think the depth is greater than nitro. Like most waterbornes, it requires good technique to spray and that is made worse by the fact that I am a lousy sprayer. I was never really able to get an "off the gun" finish and spent a lot of time sanding and polishing. It cures SO hard that if you're not polishing within a certain time of spraying it's very difficult to polish. (keep in mind I'm polishing by hand). But once polished, the depth is insane. I tried sealing with shellac and then topcoating with KTM 10 and using KTM 10 with no sealer and saw almost difference in depth and grain pop.

I've also experimented with General Finishes Enduro-Var. It doesn't wet the surface as well as KTM 10, but I'm compensating for this by using epoxy as a filler/sealer. I had never thought of epoxy as a coating, but wetting the surface out with one coat of low viscosity epoxy, sanding, then a second coat of slightly thinned low viscosity epoxy does a terrific job of popping the grain and filling the pores. It almost feels like cheating. Unlike the the KTM 10, the Enduro Var is very amber right out of the can. I'm Ok with that, but some might not like how that looks over things like white bindings. The Enduro-Var seems to spray more easily than the KTM 10 (although I might just be getting better at it) and it seems to polish more easily (which means it might not be as hard).

All this Experimentation help me understand why most folks keep going back to nitro for it's ease of use and predictability, but for me the health and explosion risks just aren't worth it.

Please keep this debate going!

pb+j · #8 06-19-2014, 12:42 PM

I saw they were close to releasing a KTM-10--but I could not find it for sale. Is it available?

Ned Milburn · #9 06-19-2014, 01:53 PM

Quote:

Originally Posted by pb+j

LOL I love both these replies!

So far KTM9 is not working for me. But this is my first time with it. It's a real pain to brush. Its going to take a LOT of sanding and polishing.

What percentage of finish applied ends of being sanded off again?

If you are brushing on, I recommend using a retarder and a quality synthetic bristle brush. The smoother you can brush it on, the less sanding you have to do. You'll be looking at sanding 25% to a third of what you put on (caveat - this is a guess-timate).

WaddyT · #10 06-19-2014, 05:55 PM

Add to all that a new Shellac finish that is now competing with U-Beaut from Down Under. The new one does not contain plasticizers like U-Beaut, which may be an advantage. I do not know what it does have in it, but it is sold as being water and alcohol proof when cured. It can also be laid on with pad or brush and leveled and buffed out to a gloss, either by hand or machine. Sounds good. I have some on order. Comes from Shellac Finishes dot com. Not inexpensive, but no more than the competition.

B. Howard · #11 06-20-2014, 05:40 AM

The easiest finish for you to do is to send it to me.

But you will do better if you pick a product and a process and stick with it long enough to start to climb the learning curve. Finishing is a whole other discipline from building.

redir · #12 06-20-2014, 07:52 AM

Quote:

Originally Posted by WaddyT

Add to all that a new Shellac finish that is now competing with U-Beaut from Down Under. The new one does not contain plasticizers like U-Beaut, which may be an advantage. I do not know what it does have in it, but it is sold as being water and alcohol proof when cured. It can also be laid on with pad or brush and leveled and buffed out to a gloss, either by hand or machine. Sounds good. I have some on order. Comes from Shellac Finishes dot com. Not inexpensive, but no more than the competition.

Excellent thanks for the tip. Looks like Robert O'Brien gave it a positive review too.

arie · #13 06-20-2014, 10:12 AM

i'm going to repost this from your thread (pb+j) on rosettes:

understandable.
-for pore fill try glaire/glare/glair? it's made from egg whites, non-tox, very old school. google it.

-not a fan of KTM myself. it kinda has a blue tint to it imo. not for me.

-on my next we're going to use polywhey. the water based floor finish. very thin, very hard, and tintable. wipe on/body-up, cut, repeat, then buff/polish to final. imo their furniture stuff is too soft. they make a "luthier" version but i haven't tried it myself. per california specs., they claim "0%" voc but ca permits "some" voc's., so they are in compliance to the ca standards, but not truly "0% voc". read the fine print. the olf forum has posts claiming glue joint separation with water based products but no real facts or pictures yet that i've seen.

-afm safecoat is next on my tryout list. they claim true "0%" voc. they make all sorts of green household stuff, caulking, paint, etc... we'll see.

WaddyT · #14 06-20-2014, 10:35 AM

The last verdict I saw on PolyWhey was that it was pretty soft. Not saying it's bad, but that it didn't solve the hardness problem some are looking for.

pb+j · #15 06-20-2014, 11:53 AM

I'm liking the KTM a little more, but that's up slightly from "not at all."

So far it's a pain to brush, and does not get very hard. It has an intense gloss and looks "deep" but there is a plasticy feel to it I don't like. Does that go away?

Advantages, though, are clear--no toxic fumes, water clean up. Did I mention no toxic fumes?

I don't think I'll use it again. But I'm going to leave it to cure for a week starting tomorrow, before I work on the top. See how it looks then. Does it cure to something closer to nitro?