Polyester Pitfalls
Old hands caution: polyester is a tricky material for the newbie to take on. February 21, 2011
Question
I have been asked to bid on a set of kitchen cabinets that require a polyester finish. Up to this point, we have only sprayed lacquer finishes. I am not familiar with this finish and am looking for some direction. I use Kremlin guns for finishing and am hoping we can use them for this kitchen. Is there a lot more involved labor wise with this type of finish, and which manufacturers are you using? I currently use ML Campbell.
Forum Responses
(Finishing Forum)
From contributor W:
Polyester can give you a strong, thick film layer. But it's quite difficult to handle. It contains three components - the coating, activator and thinner. They should be mixed in the right composition, but it has very short pot life. The mixing of the material also must be done carefully. The activator and the paint should not be mixed directly, since there is risk of explosion. You also need a clean finishing room when applying this material. A small amount of dust can be big problem for this coating.
From contributor A:
For starters, the Kremlin is not the gun for polyester. (I'm assuming you're talking about an air assisted airless.) The pot life is really short - 5 to10 minutes tops. The entire process is labor intensive and every step must be executed with precision. Polyester filler is sprayed, sanded, topcoated with 2K urethane, wet sanded and polished every day in my shop. (We use ICA products, but have been given samples by the Ilva salesman.)
With all due respect, if you are asking these questions, you'll be hard pressed to bid this job accurately. Also, a lot can go wrong in the process and a mishap can require many hours of hands on labor. Stripping the coating can prove impossible if you haven't been down that road before. Are you talking about a stained and clear or a painted finish? This is another consideration. They each have unique challenges. The polishing alone is backbreaking, and this is after hours of careful wet sanding. Don't practice on Maccassar ebony.
From contributor R:
Whose idea was it to use polyester as the coating? The stuff is bulletproof, but it's not a finish to experiment with, especially on a set of kitchen cabinets. Is there any way you could use a coating that's a bit more user friendly, maybe a conversion varnish? It's quite durable, it's available in a gloss sheen, and it sprays similar to the lacquers you're familiar with.
From contributor M:
Contributor R is right - poly is not the product you want to try on a paying customer's kitchen right out of the box. I would spray it out of a gravity gun, and please use a pipette to measure your catalyst. There are some wonderful polyester fill materials that will obliterate the grain in oak with two coats. Also remember that you are going to have to let the stuff cure, then rub it out to that 98 degree gloss that is so great. I have done the same look (not as durable) with a catalyzed waterborne acrylic. You just need to let the material cure for no less than a month in the dark. It will take the same rub out sequence (600, 800, 1000, 1200, 1500, 2000, heavy rubbing compound, two glazes) and shine.
From the original questioner:
Thanks everyone for the responses. Having considered the learning curve, it's probably easiest for me to sub out the finishing, leaving it to the more qualified professionals. It's so early in this job that we will have to see if they even go this route.
From contributor R:
I think you made the right decision. In the mean time, don't let this prevent you from doing some in shop experimenting. The polyester finishes should be added to your arsenal as they produce beautiful results, but as pointed out in earlier posts, they do require some getting used to.
The knowledge you obtain will only benefit your pocketbook as you travel down the wonderful and twisted road of Wood Finishing. By reconsidering your use of polyester, it shows me that you have already gained some preventive knowledge, and in doing so you have beaten the dreaded Murphy's Law Syndrome.
