White specs in lacquer finish

[Greg Roberts]

I’m having a problem with the finish on a pair of speakers I’m restoring.

I re-veneered in mahogany and put two coats of spray satin lacquer on them. I sanded between the first two coats.

When I sanded again to prep for a third coat, I sanded all the lacquer gently with 400 grit sandpaper, but I also had to sand a couple of tiny spots a little more to remove something I saw in the finish. Then I applied a third coat of lacquer.

When the lacquer dried and I looked over the finish, the tiny spots that I had sanded a little more had tiny white specs in them. I assumed that this was because I didn’t remove the dried, sanded, lacquer-dust good enough before putting the next coat on. So I sanded those areas again, and spread the sanding out a bit more to help blend it in, and this time I wiped them thoroughly, several times with paint thinner (mineral spirits) on a rag, thinking that this would remove the dried, sanded, lacquer-dust before I applied more lacquer.

Well that didn’t work, and now I have even larger areas (where I sanded) with white specs.

What should I do? I was thinking that lacquer thinner would “melt” the lacquer dust into the finish, but I don’t want to try that until I talk to someone about it first.

Thanks for any help you can provide.

Greg

http://www.voltiaudio.com/a/finishproblem2.jpg

[Jeff Jewitt]

I suspect your problem is the mineral spirits wipe between coats. This isn't a great solvent to use between coats, better to use Naphtha. Any small amount of MS left on the surfave (the open pores probably retain a bit after the majority eveaporates form the surface) will cause the lacquer resin to kick out of solution which is the white areas.

Scotchbrite the surface and apply straight lacquer thinner or highly thinned lacquer. Sunnyside Lacquer Thinner is a decent grade.

Jeff

[Chris Padilla]

I use Mineral Spirits all the time to clean between coats. However, I spray mostly shellac. I haven't noticed issues such as this.

I do have a can of Naptha...that stuff evaporates almost before you can use it! :)

Be sure to let us know the results of what Jeff suggested.

[james mcgrew]

mineral spirits is not a good cleaner for Laquer, use a quick wipe of laquer thinner as suggested

jim

[Greg Roberts]

mineral spirits is not a good cleaner for Laquer, use a quick wipe of laquer thinner as suggested

jim

Thank you guys.

I wasn't getting much action here, and just had to do something, so I lacquered a scrap piece of wood and sanded and wiped it with lacquer thinner. I discovered that it works really well. My concern before I did this was that I would create a sticky mess, but it was very smooth.

The problem is that when I wiped down with lacquer thinner, I had to really work at the areas with the white specs, and I ended up with an uneven finish. At that point I probably should wiped off all the lacquer until I had it all looking the same, but being stubborn, and figuring I could make it work by sanding and wiping and spraying more lacquer, I didn't do that.

So I sanded, wiped with lacquer thinner, and re-applied lacquer and came back after a few hours and I could see the dull or lighter spots where I had rubbed out the white specs.

BTW, I'm pretty sure the white specs were sanded lacquer dust in the pores of the wood, after the first coat of lacquer was applied. I should have taken more time to clean them out after the first sanding between coats.

So I went through the same process again, sanding (600), wiping with lacquer thinner, and sprayed another whole coat of lacquer. It was looking pretty good when I left the shop, but we'll see how it is in the morning.

Greg

[Phil Phelps]

Greg, you shouldn't use lacquer thinner to wipe down lacquer. It will soften, or melt through the finish. If I'm building a finish with lacquer and sanding with wet/dry paper, I'll use a damp sponge or a 100% cotton rag to clean the residue. Compress air and a tack rag wors well, but not lacquer thinner. Also, strain your lacquer through a nylon stocking and thin it at least 50%. You may need to use an exacto knife to pick and scrape away the white flecks. Good luck.

[Greg Roberts]

Greg, you shouldn't use lacquer thinner to wipe down lacquer. It will soften, or melt through the finish. If I'm building a finish with lacquer and sanding with wet/dry paper, I'll use a damp sponge or a 100% cotton rag to clean the residue. Compress air and a tack rag wors well, but not lacquer thinner. Also, strain your lacquer through a nylon stocking and thin it at least 50%. You may need to use an exacto knife to pick and scrape away the white flecks. Good luck.

Well . . .

There are a few cooks in this kitchen!

Greg

[Tony Bilello]

I agree with Phil 100%,.
A damp rag (water) will remove residue with no problem. A lacquer rag can leave rag fragments behind as it melts the previous coat and one wrong move you could create a 'hole' in the finish which may lead to having to remove all the lacquer and starting over again.
I use paint strainers instead of nylons.

[Conrad Fiore]

Greg,
You might find a more extensive answer in one of Jeff's finishing books or videos. But I think he gave you the fix for your problem by remelting the lacquer resin in those spots and then you can shoot additional coats to blend the entire surface.