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-   -   Wipe on polyurethane finish for guitar? (https://www.acousticguitarforum.com/forums/showthread.php?t=125971)

Joel 05-12-2008 11:40 AM

Wipe on polyurethane finish for guitar?
 
Minwax, for example, makes "wipe on" polyurethane finishes - both in oil and water-based formats.
Has anyone here, or any company, used something like this for guitars? I would think this would be a thin finish that everyone wants.
Are there negatives?

nehemiah 05-12-2008 12:07 PM

alternative instrument finishes
 
Hi Joel;

I am by no means an authority on finish applications, but having spent several years as a custom cabinet builder and luthier I would not suggest using any "wipe-on" finish for guitars.
The nitrocellulose lacquer used on wood instruments is designed to "flex" with the woods movement. The best (and only way to apply correctly)
is with a good spraying outfit.
I have had times in cabinet building where I had to resort to a brush or lambs wool application to do touch ups or match finishes, but you can always tell where the sprayer stopped and the brush started.
If you are thinking of re-finishing a guitar with a wipe-on finish, you will no doubt run in to problem areas around the bridge, fret board and neck joint.
The polyurethanes such as Min-wax, olympic and others are designed for use on fixed substrates, not delicate, handled instruments. In my opinion, you would not be happy with the final result. If you want to apply a finish to an instrument, try one of the aerosol cans such as Behlens nitro or Watco's
instrument finish. Just my 2 cents worth.------nic

SteveS 05-12-2008 12:11 PM

Are you building or refinishing a guitar?
There are many ways to finish a guitar. Some have used Minwax wipe on finishes. Usually it is a new builder or hobby builder. No pro shop that I know uses it. The closest I've heard of is a finish called Rockhard that can be brushed or wiped. The thinnest wipe on finish would be french polish using shellac.

nehemiah 05-12-2008 12:12 PM

wipe on finishes....
 
One point I forgot to mention......


I would avoid any finish product that is water based. water will cause cellular swelling of the wood and requires a very careful atmosphere to apply correctly. It's probably best to just avoid them all together.

Joel 05-12-2008 12:21 PM

The project is to take a "cheap" import acoustic - like the Epi EL-00 - and do some extensive modifications to it, for fun and to improve my luthery skills. This will obviously require at least a partial refin.

I've played with lacquer before: nasty stuff, and hard to work with for someone in an apartment situation, without a pro spray outfit. The aerosol canned nitro was a disaster on a warmoth Tele I built. I also don't want to expose my two daughters to any fumes. So the idea of a low VOC water based finish did seem appealing.

Nic - I'm not sure I understand your objections. Is it not flexible enough for a guitar? Poly finishes in general seem to last a long time without any cracking or peeling. I have a 36 year old Fender Mustang, and the original poly finish on it looks brand new.

nehemiah 05-12-2008 12:37 PM

Quote:

Originally Posted by Joel (Post 1477283)
The project is to take a "cheap" import acoustic - like the Epi EL-00 - and do some extensive modifications to it, for fun and to improve my luthery skills. This will obviously require at least a partial refin.

I've played with lacquer before: nasty stuff, and hard to work with for someone in an apartment situation, without a pro spray outfit. The aerosol canned nitro was a disaster on a warmoth Tele I built. I also don't want to expose my two daughters to any fumes. So the idea of a low VOC water based finish did seem appealing.

Nic - I'm not sure I understand your objections. Is it not flexible enough for a guitar? Poly finishes in general seem to last a long time without any cracking or peeling. I have a 36 year old Fender Mustang, and the original poly finish on it looks brand new.

Hi again Joel;
It's not to say that a poly finish will not last, but preparation for it to be applied is the key. Getting thru all the layers and down to the wood (or stain coat(s) evenly) is the improtant part.
Lacquer finishes are very durable and can last a long time.
The type used and the application process is what determines the durablitiy.

SteveS 05-12-2008 04:16 PM

Quote:

Originally Posted by nic36 (Post 1477274)
...I would avoid any finish product that is water based. water will cause cellular swelling of the wood and requires a very careful atmosphere to apply correctly. It's probably best to just avoid them all together.

There may be good reasons to avid water based finish, this is not one of them.
Just seal the wood with shellac before you apply it. I have finished several guitars with water based products.
Joel,
You could probably have good results with a water based product called Crystalac. The advantage of using it is that it burns into the previous coat. There are no nasty fumes and it dries pretty fast.

PWoolson 05-12-2008 04:22 PM

...and while you are sealing with shellac, why not just learn to french polish?
As Steve said, NO professional shops use any type of brush on poly. Some might use varnish but that is usually rubbed on (like french polish) rather than brushed.
French polishing is a good skill to have and is completely non toxic if you do it in the traditional way (beetle wings and everclear).

Gunny 05-12-2008 07:46 PM

I have refinished 2 inexpensive guitars with Minwax wipe on poly with the oldest job now being 4 years. For what you are describing it would be fine. I however would never finish a fine guitar with it as there are so many better choices.

It's rather easy with some good prep and patience. The finish is rock hard, thin and pretty darn glossy! It will amber up a bit. After reading various posts I decided NOT to use the water based product.

I paid almost nothing for this guitar because the finish was shot! It was a great project.

http://home.insightbb.com/~rockhe/pm20f1.jpg

http://home.insightbb.com/~rockhe/pm20f2.jpg

http://home.insightbb.com/~rockhe/pm20back.jpg

Joel 05-12-2008 08:08 PM

Bigmo,

That looks amazing. Exactly what I would be hoping for.
So I assume it had a poly finish on it when you started? Or did you sand/strip it first?


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