Jax

Hi all, just wondering if anybody has any tips for the problem i ve been having wen lacquering rounded door knobs. Keep getting bubbles on the front of them all when they dry, have put a picture to show you what i mean!

Thanks for any sugestions

cabinetman

WELCOME TO THE FORUM

Just a shot in the dark guess, could be some sort of contamination that prevented consistent coverage.

Jim Tank

try thinning the lacquer 5%. If this is on end grain, there could be trapped air (even miniscule amount) that pops the lacquer making an annoying pinhead bubble.

Leo G

What kind of lacquer, nitrocellulose or pre-catalyzed?


Either way sounds like you are putting it on the thick and the top is drying while it is still out gassing, this is called solvent pop. This caused the bubbles you see. Also what Jim said could be true. But this should only be on the first coat. After that the end grain bubble problem shouldn't happen unless the wood is extremely porous. Also if there is a breeze or a fan blowing on the pc to help it dry faster, it would cause solvent pop.

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cusingeorge

Depending upon how thick the lacquer is, 5% may not be enough.

Are you spraying or dipping these parts?

The bubbles are caused by air entrapment, coating is applied too heavy, or has a high vicosity, or is drying too fast. The lacquer is flowing into the open grain and pushing the air out, but the bubbles get trapped before they have a chance to surface, pop and flow out.

Try thinning your seal coat 15%-20% to help fill the open pores, although you may find that it takes a few more coats, thinning at this point is the best option.

You can also retard the topcoats to allow more time for the bubbles to pop and flow out, but don't retard your seal coat.

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