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I’m going to spend some time this coming Tuesday with one of the founding members of my local woodworking club, watching him spray finish on some wooden toys. He is a big proponent of catalyzed finishes. I was hoping to get some information from folks here on the OLF about catalyzed urethane finishes that you feel are good choices for acoustic guitars. Then I can pick his brain a bit about those finishes. Thanks for any suggestions.

Don, I found this intro to Jeff Jewitt’s urethane course last weekend during my Jeff Jewitt rabbit hole. I’m sure you’ve already seen it, but it’s worth sharing here. It’s a 10 minute overview of the course, and he talks about the products he uses.

https://youtu.be/osIGqddhQy0

I finished my first guitar using catalyzed polyester in 2008 or 2009. I’m not sure what kicks catalyzed urethane, but the polyester was catalyzed with small amounts of cobalt and MEKP. It was really helpful to have a few glass syringes to measure it all out.

Setting yourself up with 3M’s PPS system is going to make life really nice. The PPS system uses disposable cub liners and lids, so you won’t have to worry about cleaning the cup, and you can run solvent through the gun as soon as you’re done shooting a coat. You definitely don’t want this stuff setting up in the gun. You can set your used liner aside while the finish kicks in it, pour some solvent into a spare liner, and clean things out really fast. The liners are flexible, so it’s easy to pour the leftover solvent right back into the can. Just squeeze and it turns itself into a funnel. Alternatively, you can get a spare cup for the system to make things that much more convenient.


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Thanks, James! Yep, I had already viewed Jeff Jewitt's free intro to the catalyzed urethane online course. I have purchased other online courses on Robbie O'Brien's website, including Jeff's course on applying a nitro finish. They are very well done, and I expect this one to be, as well. I haven't pulled the trigger yet on this particular full course, but I probably will at some point (if my local spraying mentor completely sells me on the virtues of catalyzed finishes). $85.00 for 3 1/2 hours of content that I can watch whenever I want is a pretty good deal, and I really like Jeff's approach to things. And he builds guitars, so the content is even more relevant than his general finishing books and videos (which are pretty cool, anyway).

The thing that freaks me out is how dangerous the chemicals are during the mixing and spraying stages. But, once cured, it sounds like this finish is safer and less hassle than nitro, and has superb characteristics for the end user. I just need to gain familiarity, so I can take the right precautions.

Just in case others are looking for the products Jeff Jewitt references in the free video linked above, the better website to visit here in the USA is: www.ics-ilva.com.

I'm glad you mentioned the PPS system, James. I need to look into that. Thanks again.

Rick Turner got me started out right with the PPS system, and it’s a small investment.

I started out in the deep end with the polyester finish. Thankfully mixing the components wasn’t that big of a deal. Joe White gave me the tip on glass syringes, and that went a long way towards keeping everything safe. I also sprayed outside. (I’ve always sprayed outside).

It really wasn’t that bad, but nitro turned out to be so much simpler. You’re so thoughtful about everything that I don’t think you’ll have any trouble whichever route you choose.


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Definitely get the 3M PPS system no matter what you decide to spray. It makes the job so much easier.

_________________
Steve Smith
"Music is what feelings sound like"

Regarding PPS: Done! Really not a huge buy-in for the adapter and a starter kit of supplies. I can place a larger order for the consumables once I test it out. That’s a great tip; thanks!

Does anyone have any suggestions about catalyzed finishes, other than the Ilva products Jeff Jewitt uses? I’m meeting with my finisher friend tomorrow morning, and I want to ask him about specific products, if possible. Thanks for any suggestions.

I can’t wait to hear more about your experience.


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James (and all)--

I had a very informative session with my local finishing sensei this morning. He has an incredible shop; I can't describe in adequate detail how upscale his stationary machinery is. Huge, European versions of everything. The man takes his woodworking seriously.

But his spray operation, while well done, was not on the same "professional" level. Given all of the insane tools he has, I expected him to have a full regulation commercial booth (like a Binks) somewhere in his walkout basement shop. Nope; he has something much more accessible. Honestly, it wasn't that different from the setup that you see in Jeff Jewitt's videos. Sensei opens windows on the far side of the basement (it's a very large, sprawling basement) to provide make-up air. The spray booth is just a section of the basement, not completely walled off, but three sided, with a doorway to the outside. He has placed a 24" Dayton explosion proof fan in that doorway via a plywood panel that is temporarily clamped in the doorway during a spray day. When he is done, he takes out the plywood panel (with the fan) and closes the door. He has hung clear tarps from the walls, ceiling to floor. He has replaced the trough lights in the drop ceiling with LED versions. As I plan to do, Sensei runs a huge amount of air through his booth, so the vapor concentration stays very low. So, he fights explosions by using an explosion proof fan (which sees the most action) and doesn't give the vapor much of a chance to touch anything that could set it off.

This morning, Sensei (I don't have permission to share his name) used a DeVilbiss gun with a pressure pot, because he HATES stopping to refill. He uses smaller guns for smaller projects, but this morning was a large run of toys. Sensei loves the 3M PPS system on smaller guns for the smaller projects, but for this sort of project, he wanted to keep things moving, so the pressure pot was the tool of choice.

He is currently using ML Campbell products. The specific finish we were spraying this morning was Krystal satin. Sensei walked me through the process of measuring out the two parts, stirring, etc. He showed me the companion products for isolating oily woods and sealing/filling pores. I got to spray a little bit. We talked a lot about why he loves this product (not just the brand, but the idea of a catalyzed varnish). Yes, it is dangerous while you are mixing it, and it is dangerous while you are spraying it. Not so much because of an explosion risk, but in terms of breathing the product. You just have to make sure you are not breathing the product. Organic vapor masks are mandatory (obviously). Sensei used a positive pressure, full face mask, fed with air by his compressor. That was cool. I and the other folks helping with the finish line (it was a lot of toys to be moved through the booth) all just wore organic vapor masks, and we were fine. So, the stuff is dangerous, but manageable. But the upside is that, a few hours later, the product is cured and everyone (including the end user) is perfectly safe. There is none of this "wait for a month before buffing" stuff, during which the finish stinks to high heaven. Cleaning up is important and more urgent than with other finishes; Sensei soaks parts in solvent, even when using the PPS system. But for him, it is well worth that hassle.

Sensei and I talked about the Ilva products (he had not used them, but figures they are fine) and Royal Lac (same thing) and waterbornes. He has never liked waterbornes. He just doesn't like how they look, even under the best of conditions. In contrast, even regarding the catalyzed products I brought up that he had never used, he was optimistic that I would have a good experience. He thinks that, once you take the proper precautions for mixing and spraying, catalyzed finishes are just simply superior to solvent based or waterborne anything.

I'm still a bit more "big tent" about it (I see so many good looking guitars using so many types of finishes). However, Sensei has gotten my attention. I think I should look harder at the catalyzed finishes.

I see from a stroll through old OLF posts that a few people have used ML Campbell products, and specifically Krystal, with success on guitars. If anyone wants to update their experience, I would love to hear about it.

A cabinet shop I worked in didn't have the best set up for spraying (not the worst either) and decided to try krystal which is a good durable product for kitchen cabinets. The shop backed up to a residential development. The fumes that escaped from the shop killed the neighbors bushes. Krystal is not a great product for the average hobbyist. Krystal has all the nasties as nitro plus a few more - study the MSDS. Personally I feel much safer shooting nitro than I would spraying Krystal.
If you like M.L.Campbell products and want a catalyzed finish Magnamax pre cat lacquer might be a better choice.

Good to know, Clay! Thanks.

Just as an addendum to the story - the finisher ( someone I know personally and have great respect for his abilities) told the shop manager he would not spray krystal with the set up they had, so they found someone else to do it. The spray area was a separate room from the wood shop and the fan exhausted the air out the back of the building. The neighbor had complained about the smell of the other finishes they had used but after the Krystal killed his bushes he called the authorities.
After the authorities viewed the problem and the lack of an adequate spray booth, they required that a booth be installed. That situation, combined with some other areas of mismanagement caused the business to fold.
I am lucky in that the run down bungalow I have a "shop" in is a couple of hundred feet away from my house and any of the neighbors. I spray a relatively small amount of material at any given time, and if I were to blow myself up or burn the shop down it wouldn't impact the neighborhood very much. Much like your sensei I run a large industrial fan in the doorway to remove any fumes before they can build up. Also using a high pressure jamb gun with the air turned down I get less overspray (at the expense of less atomization). and a better transfer rate. I spray most things flat so I can shoot wetter coats and get reasonable flow out. It's certainly not the perfect setup, but I feel O.K. with it.
Aside from the color shift I am reasonably happy with brushing Enduro-var and will use that in the winter months when I can't spray in the shop.
We all picks our poison and takes our chances.

Understood, Clay. There are other products I am more interested in using than Krystal, simply because I have heard/seen more good things about the other products when it comes to putting them on guitars. This process of gathering info is valuable, particularly when I learn of reasons why a particular product might not be ideal. I appreciate your insight on Krystal.

I share your view of Enduro-Var. I’m happy with the result (pre-buffing) of the one guitar I have brushed it on. I’m just not wild about all of the level sanding I had to do to get to this point. I now have the ability to spray, which gives me some choices I didn’t have before. I want to gather info on those choices. Thanks for sharing your experience.

Hi Don,
I may try spraying Enduro-var at some point. On some woods the "ambering" it imparts may not detract from the end result. After I first mentioned the possibility of using a barbeque rotisserie I started digging around in my shed to find the one I never really used for the grill. I finally found it and at some point may build a rotisserie if I find it necessary to spray Enduro-var.
I don't know the particulars of your situation, but from previous posts I gather that you are very health conscious and want to avoid the deleterious effects of woodworking and wood finishing - a smart thing to do, and that your shop is in close proximity to your living spaces.
If that is the case then spraying a low odor waterborne finish, or spraying shellac with the last couple of coats french polished might be two options to consider. Unless you use some of the nastiest finishes (polyesters and catalyzed urethanes, etc) it doesn't seem like there are any "fast" finishes. At least that has been my limited experience.
The statement "A finish that’s fast,easy, non-explosive, won’t kill you (immediately), doesn’t turn blue in bright light on dark wood." calls to mind a sign you see in some shops that ends in the statement "pick any two".

Agreed, Clay. There's no perfect finish. I'm very hopeful regarding Royal Lac Post Catalyzed. I have used the original formula for French polishing, and I liked it. The Post Cat version sounds like it is very promising for someone in my situation. We'll see. I just received some. I should have a chance to experiment with it in a few weeks (too busy with work at the moment).

I’ve been using McFadden’s L4108 (two part cat Urethane Lacquer) for 20+ years. I’ve experimented with nearly every finish on the market and keep coming back to McFaddens as it’s the best product for my needs. My typical final film thickness is 1.5 - 2 mils. It’s durable, flexible, repairable and one of the clearest and most transparent films I’ve used. It’s not inexpensive and there is a 5 gallon minimum order.

_________________
tim...
http://www.mcknightguitars.com

1.5-2 mil by spraying?

Yes, spraying. It’s a matter of knowing exactly what your gun is laying down with each coat and also knowing precisely how much you remove in your sanding and buffing schedules. Then verifying it using Frisket film on the FB and bridge masking locations.

_________________
tim...
http://www.mcknightguitars.com

I don't suppose you take in finish work, lol...

I am dying to hear one of my guitars with a 1.5 gloss coat...

LOL, I’d never get any building done then. I literally spend as much time finishing a guitar as I do building one.

_________________
tim...
http://www.mcknightguitars.com

That's the truth of gloss...and why I do satin, lol.