Sanding Between Lacquer Coats

[wwwdotcomdotnet]

I can't find a clear answer in the finishing tutorials, so I figured I'd ask.

I sprayed 10 coats of Stew Mac's water based lacquer today and plan to spray 10 more. It is consistent however in some places there is a tiny bit of orange peel, and a few spaces have dust particles in them. Should I continue spraying the next ten coats and then cure then wetsand and buff, or should I wet or dry sand it now, then spray 10 more coats then cure then wetsand again and polish?

[WezV]

well if there are dust particles trapped in the lacquer you need to get rid of them.

if you want to sand it flat you can but dont be too thorough or you will sand through. avoid the edges completely till the very end!!!

once its all tidy again keep on building up your coats - then let it cure and sink

[erikbojerik]

If your water-based nitro has the same bite-back as regular nitro (i.e. the new coats melt into the previous coats without scuff-sanding in between), then this is what you want to do:

Drak's nitro schedule

[wwwdotcomdotnet]

hmm, ok i think I will sand with 400 grit to level everything, but should i wet sand or dry sand it?

[erikbojerik]

It all depends on how quickly the sandpaper loads, because once it loads then it ceases to cut properly.

If you have a compressor or something to blow the dust out of the sandpaper (frequently....), then I think you can dry sand with 400. If not, then I would wet sand with a dilute soapy water solution (use hand soap, not dish soap) and wipe the body and rinse the sandpaper frequently.

The soap is what is called a "surfactant" which means it keeps stuff from sticking to surfaces, so this helps keep the sandpaper from clogging up.

[GermanFafian]

It all depends on how quickly the sandpaper loads, because once it loads then it ceases to cut properly.

If you have a compressor or something to blow the dust out of the sandpaper (frequently....), then I think you can dry sand with 400. If not, then I would wet sand with a dilute soapy water solution (use hand soap, not dish soap) and wipe the body and rinse the sandpaper frequently.

The soap is what is called a "surfactant" which means it keeps stuff from sticking to surfaces, so this helps keep the sandpaper from clogging up.

Sorry to interrupt but somewhere (I forgot where) I read you should not use soap while wet sanding as it would damage the next applied layers of lacquer. Is this true or not?

[mikhailgtrski]

somewhere (I forgot where) I read you should not use soap while wet sanding as it would damage the next applied layers of lacquer. Is this true or not?

The Stewmac finishing book says to use soap only for final wet sanding, after all lacquer coats have been applied.

[wwwdotcomdotnet]

Ok, I wetsanded with 320 then 400 grit, and everything seems level. The finish looks a bit more milky than before, but that is expected. I just have to wipe the excess off and I will be ready to spray the rest of the coats later today.

[IPA or death]

I have always used soapy water too, but the Behlen nitro I bought says to wetsand with mineral spirits. Never tried that before but I'm going to this time. Just a thought.

Edit: Of course, you're using water-based so forget I said anything

Edited November 7, 2007 by IPA or death

[CrazyManAndy]

Most of the nitro finishers I've seen just laid down all the clear coats and then did wet sanding at the end, unless there were some dust particles during the process that needed to be removed. Obviously, that's not the only way to do it, but it demonstrates that you don't really have to do anything to the clear coats until they're all down. You can use water, mineral spirits, soap, or even baby oil to do the final wet sanding.

BTW, the stew-mac website says the water based stuff won't look glossy until you start finish sanding/buffing it out, unlike nitro.

CMA

Edited November 7, 2007 by CrazyManAndy

[Drak]

Waterbased lac is not regular lac, and gets treated differently.

I don't use waterbase lac, but I'm 98% certain that waterbase does NOT melt into previous coats, except for the coats you shoot in one day, they do melt together.

All finishes that don't melt into the previous coat have a 'window' of opportunity where they do melt into the previous coat until they cure, then there is no more 'melt-in', the window is gone.

Now, I believe waterbase builds faster than regular lac due to a higher solids content, because I would be cautious about trying to sand back to level after only 10 coats of regular lac, but you may be safe doing it with the waterbase.

If you want to give it a shot, then sand level, shoot 3-4 more coats as smoothly as you can w/ no drips/runs, move up to a higher grit and level sand again, then shoot your final few coats as perfectly as you can, then wait however long you want before doing your final wetsanding.

Note: waterbase will leave a witness line if you sand back further than your last final few coats, so be cautious around the edges, go lightly, make sure you do all the nice level sanding now or after the next set, you don't want to be doing any heavy levelling at the end, or you run a big risk of a sand-thru into your old coats and get a witness line.

ALSO: As I said, I don't use waterbase, but my common sense tells me I would be very wary of using water to wet sand on waterbased lacquer, that would be like using lacquer thinner to wet sand regular lacquer.

Maybe it's OK to do once it's cured, probably so, but I would check it out with your lacquer supplier first, and be damn sure your finish is 100% cured before you use water to wetsand it.

[wwwdotcomdotnet]

Drak, interesting point on using water to wet sand a water based lacquer. I never really thought of that. Too late now though! I wetsanded and just finished the final 10 coats of lacquer, now I'll let it cure for two weeks and see what it comes out like when i wetsand and buff it. Check the in progress forum for eventual pictures. Thanks for the advice everyone.