Re-Coat Windows for Catalyzed Coatings

Don't wait too long to apply later coats, or your finishes may delaminate.February 21, 2011

Should post cat lacquer be sprayed within a certain time after sanding your sealer coat? My boss says that we have to spray lacquer the same day we sand or it won't adhere properly. We use Chemcraft product.

Forum Responses
(Finishing Forum)
From contributor D:
Most manufacturers of catalyzed coatings strongly recommend application of the topcoat on the same day as the previous coat or sealer is sanded. Adhesion may be more or less critical depending on the product, but why flirt with the risk? It is good practice. The boss is right.

From contributor G:
The sooner you spray it after your scuff sand the better. After you sand it the coating continues to cure. After a while it has cured enough to make the coating hard enough so the scuffing that you did will no longer provide a surface that is sufficient for good adhesion.

From contributor F:
To ensure inter-coat adhesion, always sand and finish the same day. Some vinyl sealers want to be topcoated within two hours of sanding - resand prior to topcoating. I witnessed that a long time ago when a cabinetmaker shifted gears a little and made a table and chose to apply his cabinet system (vinyl sealer and pre-cat) on the table project. By the way, we always recommend conversion varnish for tabletops and at least the seat-portion of chairs. Anyway, they sanded the vinyl sealer at the end of the day, then came to work in the morning and sprayed the finish coat(s). It delaminated down to the sealer. Neither product failed, rather the sealer continued to cure after it was sanded and set up to the point that a mechanical bond did not happen when topcoated the next day. When in doubt, scuff it again (without burning through the sealer). Better safe than sorry, callbacks are profit-killers.