Using Pre-Cat as Its Own Seal-Coat
Trouble with a vinyl sanding sealer leads a finisher to consider the pros and cons of using pre-catalyzed lacquer as its own sealer. June 30, 2007
Question
I have had a lot of trouble with getting a flat coat of vinyl sanding sealer and am going to start using the pre-cat as its own sealer instead. Anyone who is already doing this have any tips for doing it efficiently? I am spraying with a pressure pot and Binks 2001 gun.
Forum Responses
(Finishing Forum)
From contributor L:
Thin it a bit more for your sealer coat than you would for your finish coats. Makes it dry quicker and easier. To use my HVLP I need to thin my material 7%, so for a sealer coat I thin it 15%.
From the original questioner:
Great tip, contributor L - thanks. Are you able to lay enough down in one coat before sanding?
From contributor L:
Yes. I don't really thin it 15% anymore unless the (ply)wood is coming out rougher than I like for the first coat. I usually just do my 7% and go for it. This way I just shoot two 5-6mil coats and I am done. If I thin the first coat I need to do another (third) coat to keep the dry mils up at 3-4 mil. If the second coat (the money coat) doesn't come out good, I still have a third coat that I can shoot without going over my max dry mil. Just watch out for your corners if you have stain on the piece. You can burn through the color pretty easy with only one (fresh) coat on.
From contributor K:
Thin down your sanding sealer and you can lay it flat. About 10-15%... Sealer is cheaper and easier to sand before the money coat.
From contributor R:
Try a higher solids pre-cat vinyl sanding sealer. Nanochem has a 30% solids that builds great. The vinyl gives you better adhesion and improved water resistance.
From the original questioner:
That's interesting, contributors R and K. I did try thinning my vinyl sealer every way but loose. It still came out lumpy. I installed all new air plumbing in my shop and added new water traps, drip legs, coalescing oil filters and a huge desiccant dryer thinking it was my compressed air that was causing the trouble with my finishes. Not!
After stripping all the sealer and topcoat off of a small millwork job earlier this month, I decided to try skipping the vinyl sealer and... bingo - the finish laid down smooth as glass without the vinyl under there. Maybe it's just the product I was using? Rodda Catalac Vinyl Sealer.
Also, are you saying that the overall durability of a lacquer finish is improved by having vinyl as a first coat? I was always under the impression that sealers make the job easier but actually weaken a finish because they have soft materials like soap in them.
From contributor L:
That is the impression I got from my distributor also. The sealers were to ease the workload, but at a cost of durability of the product. I always self seal; it makes it easier to operate the spray room. I don't have to worry about what is where and in which gun. It also eliminates one coat in your schedule.
From contributor R:
With any coating it depends on the manufacturer. Each coating is designed to perform a specific function in the total system used. Not to say that self-sealing is not okay, just that with quality products, using them as designed will produce a better result (meaning coating performance).
From contributor B:
I use a SW Unicoat product, T77, and don't thin anything but spray right from the can until it is empty. When it is factored in, the Kremlin was worth the money. My guess is if you change sprayers, your problem will go away.
From the original questioner:
That could be a fact. I only know that my rig sprays the pre-cat satin lacquer itself beautifully. Maybe I need a different fluid tip for the sealer than for the topcoat? Other factors could be the temperature in my shop was okay for the topcoat, but not warm enough for the vinyl. I never had this problem with the vinyl last summer in the heat.
From contributor B:
Try a heating wrap designed for a 5 gallon pail. I got one from Grainger. It has a thermostat and a spring catch, just wrap around the can.
