Establishing the Recoat Window for Pre-Cat Finishes

A lacquer thinner test could help you establish how much time can elapse between coats before you need to sand for good adhesion. April 10, 2008

Question
What do you generally figure the recoat window on pre-cat lacquer (Sherwin Williams) is before you need to scuff sand with 400 grit sandpaper for adhesion? The weather is not allowing me to get all my coats on in one day, so I have to wait until the next day on some of it. Would I be alright waiting overnight, or perhaps longer?

Forum Responses
(Finishing Forum)
From contributor C:
Go to Sherwin Williams' site and pull up tech sheet.

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From the original questioner:
Thanks for the response. I checked the sheet. It gives a minimum wait time to recoat, but I am looking for the maximum wait time.

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From contributor D:
Actually, it's impossible to say, as it completely depends upon temperature. For example, I often shoot panels and then place them in the Arizona sun at 160F. At that temperature whatever is going to happen to the lacquer has happened in an hour. So re-scuffing is mandatory. However, you apparently are in a cold climate this time of the year, so the window could easily be as long as a day or even longer.

I suggest you try a little test. Shoot a panel and let it dry for 6 hours, put a drop of lacquer thinner on it and see if it attacks the finish. If so, the next coat of finish should likewise be able to bond since after all, it's just resin in lacquer thinner. Then wait 12 hours and do the same test and then two days and do the same test. At some point the LT shouldn't have much affect on a catalyzed product. That's when you need to sand.