Sanding Sealer: One Coat or Two?

      Finishers discuss sanding sealers, their purpose and attributes. August 6, 2010

I've always only sprayed one coat of sanding sealer then followed it up with two coats of CV on the furniture I finish. I recently talked to a large furniture maker's finishing guys and they told me they are using two coats of sealer and two coats of CV. What's the benefit of doing this and is it something I should be doing?

Forum Responses
(Finishing Forum)
From contributor D:
I prefer to spray a wet coat 1 time for sealer and top coat. Spraying two coats will give thicker material and more build. But the thicker coat will require longer drying time. Too thick of coat applications risk getting bubble or orange peel for the finish.

From contributor G:
The whole point of a sanding sealer is to raise and fix the fuzz and nibs so they can be sanded off. Some people use the second sealer coat to get a jump on the film build. Your schedule of one sealer and two topcoats is fine.

From contributor F:
The weak link in the finishing system is usually the sealer coat. This is especially true with sanding sealers as they typically contain stearates to aid with sanding. The less sanding sealer you use the better. Some people will apply two coats of sealer to help stop burn through when sanding near the edges. Stick with your one coat of sealer.

From contributor I:
I always use one coat of sealer and if I need a higher build I use a lacquer thatís higher in solids. Sealer in designed to help you control grain raising and achieve a smoother finish.
Stick to what you're doing.

From contributor B:
Something that a most people don't realize is that you can use your topcoats as a sealer. As a former chemist in a woodcoatings lab and a finishing advisor for many different types of end users I have watched everyone from small shops to huge furniture and cabinet manufacturers think that there is something special about sanding sealers. The answer is: thereís not. Yes, as a previous response mentioned, most will contain a sanding aid called stearate that is a talc/wax that helps the surface feel smooth after sanding, but mostly loads up your paper and can also lead to a little problem called "stearate bloom". Sealers are most often lower in solids than topcoats, while the price usually doesn't reflect that. For my money I would simply use my topcoat, let it down about 10-15%, with a lacquer thinner that has a nice tale solvent and go! Most topcoats are mid, satin or flat in gloss and contain inert products to lower the gloss that will act as a sanding aid as well. Plus, you know that you have inner coat compatibility.

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