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I don't know how hazardous is polyester resin but the MEKP catalyst is apparently an explosive... saw a video where some guy soaked some in sawdust and set it off with a fuse. Makes a really loud bang.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

MEKP is no more explosive than Nitrocellouse Lacquer. ( Added/edit, they're both explosive)

Polyester Resin is EXTREMELY hazardous reguardless of how it's cured. The main ingredient of Polyester is Vinyl Benzene, also called Styrene.
http://en.wikipedia.org/wiki/Styrene

It's really troubles me when someone talks about how bad their UV cured finish smells while they're spraying it. PROPER SAFETY EQUIPMENT, AND SAFE PRACTICES ARE NECESSARY WITH ANY FINISH, EVEN WATERBORNE FINISHES.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Sorry to react to this but...the MSDS of each chemical system you use will indicate precisely how hazardous it is. The fact is...no governing agency has determined any serious health risks to moderate exposures to polyesters.

Let me give you an example:

I had a business wherein we sprayed polyester calalyzed with MEKP every day. The only ventilation was a large door at one end of the room. Often in the winter that door would remain closed all day. Don't get me wrong. I MADE everyone wear respirators...but the State of Washington, after having evaluated that environment using sensors which were attached to several of my employees for the entire day, classified my business in the voluntary category...meaning the employees could decide for themselves whether or not they wore a respirator. As thick as that styrene smell could get in there I would never dream it was safe not to use a respirator....but there you go. Of ALL states, Washington State is the LEAST cavalier about chemical exposure in the work place and they shrugged their shoulders at what I thought to be a fairly high exposure to polyester.

I'm experimenting right now on test panels with a sample of a catalyzed polyester system made by Seagraves Coatings. So far, I'm impressed enough with the processing of it to believe it would be ideal for my electric guitars. The main draw for me is that if I want to go from raw wood to polished finish I can get there in three days. My main problem is that the company samples quarts but won't sell anything but five gallon pails. So...with sealer and topcoat I have to invest quite a bit of cash into the system before I can actually use it on a guitar.

I'll be looking at other polyester manufacturers as well as catalyzed urethanes....but I'm certain now that catalyzed systems are the way to go for me.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

A friend of mine who manages our local autobody supply shop has been advocating this technique to me. I am wondering if or what barrier coat is used between the two (Shellac)?

I was always under the impression that it was the isocyanates that made the 2 part polys have an added danger/health hazard along with the usual danger/health hazards of finishing.

What I do is to put on all the coats of lacquer and not touch it until it has cured. Lacquer will shrink into the pores... that is the reality of the stuff and if customers can't live with it, then they can go with someone else who can finish it in poly. I personally don't like it.. you can't repair it and you need a lot of support equipment to spray it.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

I believe that lacquer can be sprayed over polyester without any barrier coats; just sand the polyester level, and proceed to shoot lacquer.

Polyester can be repaired faster in the shop than any other finish, even lacquer. The "trick" is that we have to re-finish an entire panel, and not just the little scratch or ding(talking new instruments, here). It's very counter-intuitive to strip an entire side, top, or back just to fix one tiny flaw, but in reality, it's all done quickly and ready to buff again in 1 to 3 days. Can't level and buff a lacquer drop-fill in 3 days and not expect it to shrink-back....

On existing instruments, polyester can be repaired, very successfully, using a drop-fill or small brush for small areas/scratches/dings with minimal "witness marks" if you're buffing techniques are up to snuff(most repair-only shops' buffing setups and compounds aren't up to snuff for polyester), or again, an entire panel re-finished or lightly over-sprayed.

The repairability of nitro lacquer is grossly over-exaggerated, because it will shrink forever, and will yellow with age, such that the repair you did today will show a slight depression in a few years, and the thicker "build" of lacquer in that ding or scratch will yellow more than the surrounding lacquer. A nitro lacquer repair only looks "invisible" for a rather short period of time(relative to the actual life expectancy of the instrument).

I have a friend who worked many years in a fiberglassing factory, building canoes, trailers, all sorts of large things. They only wore respirators when spraying "chopped" fiberglass. Otherwise, they didn't wear any breathing protection. Skin contact, on the other hand, must be avoided at all costs, especially with cobalt, MEKP, and MEK. Me, I have a full-coverage, positive-pressure air supply hood and special jacket with long wrist sleeves that I wear for spraying, as well as double-gloving(over and under the wrist sleeves). I leave the entire shop between coats, carrying a simple kitchen timer with me to remind me when it's time for the next coat. Needless to say, I do most of the spraying in the evenings, so that when I return the following day, a 10 minute blast with the booth blower will clear the shop of all remaining nasties and smells. Compare that to nitro lacquer off-gassing most of its nearly 80% solvents in the first two weeks. THAT is how I became sensitized to nitro; working in a small space with constantly off-gassing nitro. I'd spray outside, but hang the instruments inside(of course).

Nothing about my methods have changed; can't speak for others. My only "beef" is still with the barrier coats(IE: rosewood sealers). high costs and uber-short shelf life sucks... Would love to find a supplier who would sell small packaged quantities; I typically only need 1 to 2 ounces of Isolante(barrier) and 1/2 to one ounce of the hardener for a guitar's body and neck, yet as soon as I open the gallon containers of each, they begin their slow march forward to their death.... <lol> I've tried re-packaging a new gallon of each into smaller containers(125ml jars), and even with zero airspace, most of it will still go bad before I can use much of it. Frustrating, and wasteful.

I do the chemical cure; cobalt and MEKP. Plenty fast, plenty safe, and arguably and more "complete" film cure. I can't see the need for a UV system for my requirements, and definitely do NOT want to make my spray schedule dependent upon the weather forecast. Not to mention that full-on exposure to direct sunlight can and will cause a drastic rise in temperature to all darker woods, very quickly...

I'd personally never trust a bridge glued to the polyester; I know it's been done, but....

I swear I've refinished several instruments out there that looked as though the bridge was glued right to the still wet polyester... the glue looked like some kind of a glass like plastic, not unlike the material the finish is made of. Polyester has this sweet smell when you sand it.

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Cat-gut strings are made from kitten guts, stretched out to near breaking point and then hardened with grue saliva. As a result these give a feeling of Pain and anguish whenever played, and often end up playing themselves backwards as part of satanic rituals.

Typhoon Guitars
http://www.typhoon-guitars.com

I've been told that Larrivee used to glue their bridges on top of the Polyester finish,(with CA gel) but no longer do. I'd never do it.

Grumpy, I transfer my isolate to small containers, top the containers off with propane, then put them inside a zip lock bag, also filled with propane. During the Summer I keep the bag on a shelf right next to my AC unit to keep it cool. I'm currently using some that's over a year old. They brand I use has a recommend shelf life of 3 months. You can tell if it's bad (before it turns to a white glob) by holding some, in a clear container up to a light. If it looks like it's got tiny marbles floating around in it it's bad. Propane works just like bloxygen, except (obviously) it's flammable. I've been told bloxygen is argon. I used to use argon, but sold my welder, and no longer have a bottle of argon handy.

_________________
I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

I swear I've refinished several instruments out there that looked as though the bridge was glued right to the still wet polyester...

There are a lot of guitars with their bridges super-glued directly to the polyester; like I said, I know it's done, but... You won't see me doing it!

Woody, thanks for the propane, and argon, tip! Must to try.... What brand of barrier are you using?

The barrier I use is Axon ISC-909/ISB-910. I use their PST-902 top coat. http://www.axonproducts.com/Web%20Pages/ProductList_Wood.aspx

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Thanks Grumpy for the informative reply, and Woody for the tips.

Grumpy - who's the Canadian distributor for Chemcraft? Their website is a bit of a bear to navigate.

Thanks

http://www.akzonobel.com/wood/wood/our_brands/

Or:

Akzo Nobel Wood Coatings Ltd. 155 Rose Glen Rd. N.
Port Hope, ON L1A 3V6
Canada

phone: 905-885-6388
fax: 905-885-7587

Their website is terrible(and currently down...); I just call them and ask to talk to someone in the lab, who will give me the part numbers I need, and I then call the nearest retailer with an order. A bit of a runaround, but methinks their intention is to always have you speak to "an expert" to help you chose the correct product. I still call before ordering, despite having part numbers for what I need now, just in case there's something new or better. Been thinking of giving ICA polyester and their barrier a try...

Thanks Woody; they don't appear to have a presence north of the 49th, though....

I don't know. They're ~60 miles from me.

_________________
I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/