I am about to teach myself spray finishing prior to finishing a set of new bathroom cabinets that I’ve built for our house. I’m corresponding with AccuSpray for an HVLP system that should fit all my finishing needs for the foreseeable future.
Question – one of my acquaintances swears by precatalyzed lacquers and enamels that he purchases from the local automotive finish supply house. Have any of you folks experimented with this type of finish for woodwork? If so, what has been your experience?
Replies
Hey Mike,
PreCat lacquers are common in the furniture industry. I'm not sure what differences there are between those finishes and automotive finishes, but if you can get the clarity that you want, it surely will be durable enough.
I'm looking into the subject myself, as I want to use exterior grade PreCat on my next longbow. I'll let you know what I find out.
Tom
Thanks, Tom, I look forward to your report.
Word around the cracker barrel is that, with the advent of plastic bumpers, thinner flexible door panels, etc, that automotive paints have been reformulated to be less rigid and brittle, and more pliable, i.e., less likely to craze and flake off of automotive parts that flex.
On a separate note, I seem to remember seeing an add a couple of years ago in either Fine Woodworking or Fine Homebuilding (or This Old House?) for a finish that the company claimed was so flexible that it was ideal for use as a finish on long bows. I'll poke around in some back issues and see if I can come up with the reference.
My main concern is relative to what special problems, steps, techniques, or precautions must you take to successfully spray pre-cat in general and precat automotive finishes, specifically.
Edited 8/28/2006 8:40 pm ET by Mike
Lacquers seem to be giving way to acrylic enamels in the automotive world and with a lot of them you add an isocyanate hardener or to make it flexible a flex agent.One point I would make strongly is be very careful of the isocyanate hardener.It is very toxic and you will need an air fed respirator not a filter cartridge also full tyvek suit with hood.I have a good friend who got very sick from this.Funny thing is it doesn't smell as bad as precat nitro sort of a sweet smell.
I have used sherman williams Precat solid colour finish and it is great. I have also used automotive paint (PPG) of the same type. I used it because the piece had to match a motorcycle and the client had the same paint left over from the bike. I don't know that there were any problems with the auto paint on wood, but I didn't like using it. I kept having visions of peeling paint. But the piece is in Detroit now so who knows. The Sherman Williams product is engineered for wood and they also have a conversion varnish that is even better.
Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
Hi Mudman,
Well, it's certain that this next project uses skills that I don't have and tools that I don't yet posess.
I think that I'll practice on the Buick before I approach the bathroom cabinets. I'd hate to have to make them over due to a botched paint job.
Mike
You don't say where you are, but you might want to find out if there are any local restrictions on using pre-cat finishes.
A few months ago, I connected with a finish guy who now does all my color matching work. (If I match a color/finish, it's pure luck. He actually knows what he's doing - lol.) He was telling me that I wouldn't be able to buy them since I don't have an approved spray room and proper storage facilities.
Even if you have no restrictions, be careful with them - they can be really toxic.
Thanks guys,
Based on your's and other's inputs, I think that I'll wait until I have a bit more experience with spraying overall before I tackle something that is evidently as toxic as the automotive sprays.
Since my garage (where my spray booth is) shares a common attic with the rest of the house, it would be a real bummer to make the rest of the family ill, as well.
Mike
Probably a good plan, Mike. I was at my finishers shop a few weeks ago while he was spraying a set of cabinets. His spray room (not a booth, a room!) has one entire wall of filters and fans and the city apparently has very strict requirements about air flows, filtration, etc.
He waved me into the room and - even though he hadn't been spraying for several minutes - the fumes had me half dizzy (dizzier?) within a couple of minutes.
I use a lot of polyurethanes when I do my own finish work and even those annoy SWMBO if I leave the door open. I hate to think of how she would carry on if I were using some of those pre-cats - lol.
Rumpole of the Bailey, Is that YOU? I haven't seen She Who Must Be Obeyed for a good long time, how IS the old girl?
I haven't seen that show for quite a while either, but it was one of our favorites (oops, favoUrites). SWMBO used to get annoyed when I referred to her as SWMBO, but now she seems to be pretty much resigned to it - lol.
Hey Guys,Okay, a little more information: I've checked with three coating manufacturers in the past two days, and everyone of them has assured me that acrylic lacquer, with a flexible plasticizer additive will produce a finish that has superior durability, cold resistance and flexibility to that of ordinary acid precatalyzed nitrocellulose lacquer. This is what I'm looking for, because I'm tired of having to recoat longbows that have "cold checked" as they age.That said, they also all agree that an isocyanate catalyzed urethane is has superior strength and flexibility to any lacquer. My problem is that I've just sprayed enough isocyanate coatings in my young 48 years that I'm not willing to subject myself to it anymore. So lacquer it is.Here's link to a short treatise on lacquer that serves as sort of a primer (no pun intended) on evaporative coatings. http://www.woodfinishingsupplies.com/Lacquer%20by%20Design.pdf#search=%22acrylic%20lacquer%20flexibility%22Tom
So lacquer it is.
In that case, thinner is better. The thinner the dry film is the more flexible it will be. Nitro lacquer in particular behaves better with thinner dry film coats than with thicker ones - which are prone to chipping etc. The thick versus thin and how flexible they'll be holds true for a broad range of finish materials. But, lacquer is particularly known for thick film brittleness whereas it's actually pretty flexible with a thin build.
That said... there are non-catalyzed urethanes out there which provide the properties of a urethane without the isocyanate issues.
One such clear which one wouldn't normally think of using on wood is DuPont's new line of water-based Imrons. The solvent-based Imrons have a long and storied reputation as serious health hazards to work with. But the water-based Imron has no isocyanates (although it does have methyl pyrrolidone) and is insanely flexible just like all Imrons are. I do know that based on my own testing it loses it's flexibility after several years. But for the first couple or so years it's far and away vastly more flexible than any other clear I've ever worked with. I mean it's almost absurd how flexible it is... like a plastic sandwich bag.
I used to have a strip of it here on my desk at work that I would show folks from time to time. Lots of dropped jaws when I told them when it had been sprayed out. It did finally get relatively brittle, though. And at that point it crumbled up like most other clears would have after a month or two of dry time.
Hey Guys,There appears to be some confusion regarding the difference between pre catalyzed lacquer and two part catalyzed urethanes. Precats are acid catalyzed lacquers that use regular lacquer thinner and are applied as one part. Catalyzed urethanes (post cat.) are two part finishes that use polyisothiocyanate catalyst, and generally a methyl ethyl ketone thinner.Precat lacquer has been used in small furniture shops for years, and with the usual precautions against organic solvents, a hobby shop should be able buy and use it. The isocyanate catalyst is definitely more dangerous stuff, as it tends to attach to respiratory pigments like hemoglobin etc. It is the compound responsible for the Bhopal disaster in India, back in the 80's. Overexposure to MEK can cause damage to your central nervous system.I've sprayed both products; precat on furniture and cars, and catalyzed urethane on airplanes. I'll continue to use precat, but I'm done with urethane.Tom
I see no reason why automotive clears can't or shouldn't be used on wood. I've worked with automotive clears for about 10 years now and with wood clears for another 10 years before that (and still do). But I've never heard of a precat automotive clear.
In general I think you'll find that wood clears are easier to work with and to apply on wood than automotive clears. Automotive clears are designed to sit on top of a surface and to build in film thickness. Whereas wood clears are designed to go on a more porous surface and thus tend to be less viscous and flow out better because film build thickness is almost a secondary factor with wood finishes. Plus, automotive clears are designed to be very glossy. They can be flattened out with an appropriate flattening agent (not all automotive clears have an appropriate flattening agent though). But the lower the desire sheen the more difficult it is to get an automotive clear to come out a uniform sheen. If you are wanting a very glossy finish on your wood then that's not even an issue. If you want something in the lower sheen ranges though I think you'd definitely find automotive clears much more frustrating to work with than wood clears.
There are difference between automotive finishes and wood finishes. Automotive finishes will not stand up the the movement that wood is subject to. It is not flexible enough. Some will use automotive finishes on substrates that don't move much like MDF but even that can be problematic.
There are two part lacquer finishes that are designed for furniture. A number of sources carry them. The two part finishes are almost bulletproof but be sure use the proper respirator and protective clothing. Read the MSDS.
You are better off to stick with finishes formulated for wood applications.Howie.........
Edited 8/29/2006 11:03 am ET by HowardAcheson
Mike,
I echo what mudman says about the sherwin williams line of clear finishes. I build cabinets for a living, and I use their sher-wood water white conversion varnish. Comes in gloss, bright rubbed, medium rubbed, or flat sheen. It's a 2 part mix (clear + a small amount of catalyst), pot life is 24 hours after you catalyze. This stuff is amazing, dries fast and has something like 54% solids. so 2 coats and it almost looks like it's coated in plastic. Very clear, so it's recommended for sealing over light colored paints or white pickled finishes but I haven't used it over paint, just stain so far. I have used PPG brand automotive catalyzed finishes as well in the past on wood (guitars), they are a bit pricey for the clear and catalyst (and reducer) to use on cabinets. I think I'm paying $25.99/gallon for the conversion varnish, and about $16 quart for the catalyst, which does about 8 gallons of clear. Thinning and clean up with xylene.
Good luck,
Lee
25$ for the white water!! I think I am paying closer to 50$. Ohh wait.... You mean for the clear finish I bet. The high solid tinted finish version is like 50$ and I can only buy 5 gallons at a time.
Another huge advantage is that it is self sealing. No primer necessary. It dosent sand quite as nice as the recomended vinal sealer but for small jobs it is faster to not have to remix two batches of finish.
Lee, have you tried their water base version of that finish? I have a huge job that needs to be finished on site and ventilation is nonexistant....literaly. I am thinking about trying it but I am a little aprehinsive about trying something new on an importaint piece.Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
Mike,
Hi, no I haven't tried the water based version. I would like to, but as you said, a bit hesitant to try something new on an important piece. Right now I'm spraying outside as I have no booth, but the winter months are approaching and I won't be able to do that for more than a few more months and then I will have to set up shop indoors to spray. If you try it out, let me know what you think, my email is [email protected], and if I get a chance to try it out first, I'll drop you a line.
Lee
will do. Change sucks...Pardon my spelling,
Mike
Make sure that your next project is beyond your skill and requires tools you don't have. You won't regret it.
Hey mudman Mike
You always end "pardon my spelling", and I would have to do the same except that I discovered that if I jump to the bottom of the screen when I've written a post, and before I post it...
there's a SPELL CHECK bar. The darn thing does wonders for my terrible spelling.
Mike D
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