Tom Jr. - Posted - 12/14/2009:  13:22:25

There are products to keep lacquer from blushing when the humidity is too high by slowing down the drying time(retarders). Just for example say, one has a woodstove heated garage with very dry air are there any drawbacks to that.

I understand that the ideal temperature for spraying the finish is 72 degrees but what about after you spray your three coats an hour apart in a day. Would (did you catch the pun) a good hot fire warming the place up help speed up the drying/curing process. Sort of a "baked on" finish.

It takes weeks for the finish to cure enough to buff as I understand it and I'm not much for rushing stuff. I'm more liable to go cut down a tree and wait for it to cure for years when I have a project in mind however like the old song goes, "Christmas time's a comin". Would a warmer temperature with little to no humidity be a good thing for curing?

Square Neck - Posted - 12/14/2009:  16:09:18

From what I have seen....the more dry the better...

But I don't paint guitars.....more along the lines of cars and old bicycles so get a few more opinions please LOL

oldredneck57 - Posted - 12/14/2009:  16:13:33

My concern would be more about the open flame and spraying any type of paint. I would recommend heating it up first, shutting down the flame and then spraying.
You could try using ultraviolet lights to help with drying.

Dan Brooks - Posted - 12/14/2009:  18:52:34

Tom Jr.,

A few things. oldredneck57 is right about some risk with the gases in the presence of your wood stove. Even with great ventilation I'd probably be on pins and needles.
Second, that wood-heated air is bone dry. It may make a coat of lacquer dry a little quicker but it could wreak permanent havoc on the wood, glue joints, etc. And it is no real help toward "curing" the finish. About 40% to 45% RH is optimum...for the wood AND the lacquer.
The best way to speed up the CURING (not drying) time is to wait 3 or 4 days and give it a good scuff sanding with some 800 grit dry sandpaper. In another 3 days or so scuff it with 800 again. The curing process is actually the release of the chemicals and gases that are used as propellants, thinners and emulsifiers within the lacquer itself. Breaking the surface early a couple of times can really speed up that process. On my guitars I generally wait 3 to 4 weeks before final sand-out and buffing. By using the method above you could knock at least a week off the wait time.
My two cents.

Dan Brooks
B & B Resophonic Guitars
therarelyherd.com/documents/27...tion=show

Edited by - Dan Brooks on 12/14/2009 19:03:30

Dan Brooks - Posted - 12/14/2009:  19:16:41

Tom Jr.,

I'm following myself up here. 72 degrees may be an "optimum" temperature for spraying lacquer, but I've sprayed anywhere from 50 degrees to 90 degrees and as long as the the humidity was within the 40-45% range, I had no problems. Nitrocellulose lacquer dries to the touch almost instantly anyway so cranking up the heat won't serve you any purpose. It can't be "baked on".
I know I'm repeating myself, but a reasonable temperature, 40 - 45% RH, and then using the early scuff method I mentioned will give you the best results.

Dan Brooks
B & B Resophonic Guitars
therarelyherd.com/documents/27...tion=show

Edited by - Dan Brooks on 12/14/2009 19:17:27

benspinks - Posted - 12/15/2009:  00:13:10

Good air movement will also help.

Ben

Tom Jr. - Posted - 12/15/2009:  05:04:56

Thanks all for the input. I am a little concerned about the flammability issues and I hope my spray guy keeps the fire out or sealed during spraying. He is like Squareneck in that his area of expertise is bodywork/motorcycles (his work has been on the cover of Easyrider) and does a great job with the paint gun but doesn't know wood. The last one I sprayed turned out decent but not great. My expertise is really with a case of Krylon paint cans, a case of beer and an old truck with friends.

It is supposed to be about 50 here for the next two days so I think everything will be OK. According to the instructions from Grizzly, first day is spray a coat every hour for three hours, wait a day, sand, spray a coat every hour for three hours, and same on day three. Then wait a few weeks and final sand and buff. Step 15 actually says, "use guitar as mirror to fix your hair".

I have never heard of the sanding trick to speed up curing time but that makes a lot of sense. I'll probably try that. The project will be completed without final buffing, strung up and gifted, and then brought back to the shop to pretty it up after the curing process is complete.

ravedog - Posted - 12/16/2009:  06:34:05

if you'all are in a big hurry.........
I took the tour at taylor guitars last week. their proces goes from sanded body-to-sprayed finish-to- cured finish---to first buffing in less than 5 minutes. all you need are special systhetic formulas and a
million bucks to do it in your home shop...! !
ravedog

benspinks - Posted - 12/16/2009:  06:58:48

There are quite a few going over to UV. Most likely a thinner finnish, but a much harder, more dence coating. Most often they are 100% solids, but it does vary. Better for the enironment either way. Not nice to get on your skin though. I have a friend with the skin grafts to prove it.

Ben

Alan Rausch - Posted - 12/16/2009:  11:19:30

Go on line and check out Stewart Macdonald, there is a quick 2 page instruction for nitro-cellulose spraying. I re-finsished my mahogany Tut Taylor this past summer. I did 12 coats or so after filler, sanding steps. Sand with 1500 or grit (wet), then use polishing steps. I waited 1 day between coats, which extends work time, and put the guitar in the back of my Jeep Cherokee, which stayed about 100 degrees in summer, partially shaded. I talked to a luthier who is certified for Martin repair and Martin suggested a cabinet with a heat lamp, this also stays at about 100 degrees. I bought a kit form Stu-Mac for $120 or so which gave me everything I needed.

Tom Jr. - Posted - 12/16/2009:  12:53:44

There will be some heat I reckon. Maybe not 100 degrees but warm enough anyway. I spent the morning spitting firewood for the spray guy and he has a decent wood stove in the shop. In general the air is not very dry right now. The first couple of coats sprayed on at 52 degrees and damp got a little bit of blushing on just the back of the neck but that eventually went away. It should have at least one more coat on it right now and two more before sunset.