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Pretty sure I know the answer, but...is there any way to chemically strip a UV finish, or does one need to bust out the 80 grit?

I believe even 80 grit is slow going. I'd remove most (all probably) with a cabinet scraper.

I've used "Aircraft Remover" to strip thick Poly finishes on electric guitars a couple times. I can't say for sure they were UV cured though. But the stuff is evil and seems like it will strip anything. I bet they have a list of finishes that they work on if you Google it.

If you can find a stripper with a high percentage of Methylene Chloride in it and score the finish in several places it may work for you. I think scoring the finish allows the stripper to get under it a little to lift it.
It is getting harder and harder to find solvents that are as effective as the old ones. Even some of the "green" products have been eliminated. The EPA has banned Methylene Chloride for consumer products in the U.S., but Industrial use is still allowed. Maybe you can still find it in Canada.

MEC was taken off consumer shelves beginning of 2019 in the USA so the only option is mechanical removal.

The stuff is tough and a scraper is even slower than paper. Heat gun and scrape is the best solution and even then the stuff is tough.

So why are we removing it?

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

I’m considering refinishing a top in FP for performance improvement...

I understand your pain, Ed. I've done my fair amount of stripping poly this year only to send my work out to someone new - and then strip it off again. I will never trust another soul again to do my finishing work

BTW, you might try an oil varnish. I get the same tonal improvements with varnish as I do with a French Polish. It's a bit easier to apply and a bit more durable as well. Unfortunately, not as easy to repair tho'.

Sorry to hear of your troubles. Gloss finish really is a bore...

The SDS shows aircraft stripper to be 60 to 100 percent Methylene Chloride - it must be good stuff!
If you are an industrial user (and possibly a commercial user) the stuff is still available. I guess they assume those users will understand the associated risks and take reasonable precautions.
I wonder how hard it is to make that stuff? (might be a bad idea - I've read a teaspoon full of pure MeC is deadly)

It looks like it can still be bought by consumers in Canada (just not from Canadian Tire).

Copied and pasted from: https://fscimage.fishersci.com/msds/91858.htm

[i]Appearance: clear colorless liquid. Flash Point: 52 deg F.
Danger! Causes irritation and possible burns by all routes of exposure. Poison! Flammable liquid and vapor. Harmful if inhaled. May be fatal or cause blindness if swallowed. May be absorbed through intact skin. May cause blood abnormalities. May cause central nervous system depression. Potential cancer hazard. May cause liver, kidney and heart damage. This substance has caused adverse reproductive and fetal effects in animals. Cannot be made non-poisonous.
Target Organs: Blood, kidneys, heart, central nervous system, liver, eyes.


Potential Health Effects
Eye: Produces irritation, characterized by a burning sensation, redness, tearing, inflammation, and possible corneal injury. May cause painful sensitization to light.
Skin: May be absorbed through the skin in harmful amounts. Prolonged and/or repeated contact may cause defatting of the skin and dermatitis. Causes skin irritation and possible burns.
Ingestion: May be fatal or cause blindness if swallowed. May cause gastrointestinal irritation with nausea, vomiting and diarrhea. May cause systemic toxicity with acidosis. May cause central nervous system depression, characterized by excitement, followed by headache, dizziness, drowsiness, and nausea. Advanced stages may cause collapse, unconsciousness, coma and possible death due to respiratory failure. May cause cardiopulmonary system effects. Advanced stages of Dichloromethane exposure may cause collapse, unconciousness, coma and possible death due to respiratory failure.
Inhalation: Harmful if inhaled. May cause adverse central nervous system effects including headache, convulsions, and possible death. May cause visual impairment and possible permanent blindness. May cause narcotic effects in high concentration. May cause blood changes. Overexposure may cause an increase in carboxyhemoglobin levels in the blood. Can produce delayed pulmonary edema. Causes respiratory tract irritation with possible burns. Causes irritation of the mucous membrane.
Chronic: Possible cancer hazard based on tests with laboratory animals. Prolonged or repeated skin contact may cause dermatitis. Chronic inhalation and ingestion may cause effects similar to those of acute inhalation and ingestion. Chronic exposure may cause reproductive disorders and teratogenic effects. Laboratory experiments have resulted in mutagenic effects. Chronic exposure may cause lung, liver, and pancreatic tumors. Prolonged exposure may cause liver, kidney, and heart damage.[/i]

Let's see: Blindness, cancer, liver, kidney and heart damage to name but a few. And an alarming property of flash point at 52 degrees F.
I know you asked about stripping UV Poly and my advice has nothing to do with that. If you really feel the sound is being compromised by the impermeable finish and if I were in your shoes I would re-top the guitar.

_________________
Stay with the happy people.
--Reynolds Large

I've successfully stripped polyester off a soundboard while removing a negligible amount of wood from the top (which was my main concern). In my experience, the poly tends to rest atop the wood -- so sand aggressively until you get to the stage where you begin to see raw wood exposed. The wood sands more easily than the poly - so I used a razor blade to scrape just the polyester areas. This takes time but eventually you are left with a surface that you can then clean up with 150 grit. I used a sanding block and was able to fully remove the polyester and then fine sand to 220 grit. It worked perfectly but it was indeed a lot of work. The back/sides/neck are much easier to attend to but the top is challenging because it's easy to eat away at the top and alter the thickness if you aren't super careful. All told, removing the poly from the top took me about 4 hours but it can be done. Personally, I'd prefer doing this Ed than messing with these dangerous solvents/solutions.

Best of Luck !!!

If I could get the stripper I would use it - outdoors with good ventilation. I would use a gel type and stay away from the edges of the top so there is no chance of it dripping over the side. The remaining finish left at the edges I would scrape off and then lightly sand the entire top. Methylene chloride is nasty stuff, but so are a lot of household cleaners we use without giving any thought to it. I wouldn't want to use that stuff to strip furniture for a living as some have done, but occasional use with reasonable precautions is probably no worse than the occasional cigar and shot of bourbon many enjoy.

The stuff killed a co worker of mine years back....It is nothing to be trifled with!

_________________
Brian

You never know what you are capable of until you actually try.

https://www.howardguitarsdelaware.com/

In the early 70s I had a job helping a furniture finisher for the unfinished furniture stores in the SFBay area. He got a 55 gallon drum of the stuff and had me dip dining room chairs in the barrel to strip them. Chemical gloves, goggles and long sleeves were the only protective gear provided. I don't recall any breathing protection. Could have been the start of my lifelong high blood pressure issues. Nasty stuff. It sure burned when splashed on skin.

Methinks it’s more bother than it’s worth...

I was wondering about the flash point data TRein posted because Methylene Chloride generally needs higher temperatures to combust. His data is for a 50% methanol/50% methylene chloride mix. One advantage of MEC strippers is that many of them are listed as non flammable. Many of the health effects listed are those listed for methanol, another nasty compound one should be careful using. They may or may not apply to MEC (but it has plenty of its own).
I wouldn't advocate buying a drum and bathing in the stuff, but for the occasional strip job, used carefully, it works well. You have to be careful who you work for - jobs that are nasty and deadly get passed on to the young callow workers who don't know any better.

The advantage of using a stripper is you aren't losing any wood.

Yes, not losing top thickness was the aim of stripper...

So in other words, to use strippers that actually do the job, you'll need eye protection, and organic respirator, and skin protection...i.e., what non-idiots wear to work with hazardous chemicals.

Buy aircraft stripper...it still contains stuff that strips linear polyurethane and other tough aircraft finishes because it is not an option to sand off aluminum cladding on aircraft panels carrying the paying public. We went through this last year with stripping of Enduro-Var...nothing worked except for methylene chloride.

http://www.kleanstrip.com/product/aircr ... nt-remover

_________________
For the times they are a changin'

- Bob Dylan

What does this stuff do to glue joints - anybody know? It seems hide glue would be susceptible to some deterioration if this stuff got on it.

When I was 20 I worked at a place called Strip-a-way
We had 3 tanks....
The first tank had 300 gallons of Methylene chloride, the 2nd tank had 750 gallons of cold lye and the 3rd tank had 500 gallons of dilute hydrochloric (muriatic) acid.

We stripped doors, woodwork, furniture and radiators etc. We even did a solid body Fender guitar once.

After the item soaked in the methylene chloride for a short while it was scraped and brushed, then weighted down in the tank of lye for an extended period (sometimes hours) depending on how much paint was on it.

The furniture that had varnish or lacquer was quick and after the lye-which darkened the wood the acid neutralized it.

After that it was hosed down(80 lbs. pressure) and left to dry.

The majority of the old furniture were held together with hide glue or other water soluble glue.

They seem to withstand this brutal treatment quite well.

Furniture that was dip stripped had a reputation for eventually coming unglued around here, but that could be a function of how long it spent in the tank, and what was in the tank. I've stripped a few pieces with MEC, but generally that was not a part of the furniture industry I was interested in being in.
I think the long term effects of constant exposure to it are not good and even the short term affects can be bad if it is carelessly used.

Ed, from my inexperienced perspective, I'd be entertaining the idea of retopping the guitar and not considering the mess and toxicity of stripping. But the fun never ceases: what's to do to integrate a new top's finish with the rest of the uv-finished instrument? And if this is one you built, would it be less overall nuisance to build another for the customer and take this one back sell this one yourself as-is?

_________________
Peter Havriluk

I'd rather refinish than retop, but, it really seems more bother than it's worth, especially as it's not something I actually -need- to do...

Didn't someone at Martin once say that they didn't worry about how individual guitars sound, because there was always someone who would like it and buy it?
If the guitar looks nice and sounds O.K. then that is probably the thing to do. And who knows - it may develop a really great sound in time, or it may stay less responsive and sound great amplified. Some people never change their strings because they prefer the sound of dead strings. The guitar may not sound as good as you think it should, but it probably doesn't sound as bad as you think it does. Calling it "done" and moving on might be the best course of action.

There was an interview with Manuel Velasquez years ago in American Lutherie. He had a friend who had success removing this kind of finish with a clothes iron. Obvious issues to consider doing that.