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Sprayed the 1st coat of colortone waterbased lacquer this afternoon. Thought the spaying went well. No sags or runs and not too dry. But, 45 min later, the finish looks like a mini version of the salt lakes. There are small spiderweb cracks throughout. Temp was about 65 doegrees in the booth. The shop is pretty dry (around 35% rh), could this be causing the finish to dry too fast? Have any of you experienced this? Do I need to sand all this coat off or will it even out with more coat (after the root cause of the problem has been addressed)?

Thanks,
Aaron

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Aaron Craig

So far no solution. I have done some further test. The temp in the boot was increased to 70 degrees and 50% RH (the Colortone directions say 70 degrees with 45-60% RH is ideal). I sprayed multiple pieces at varying thicknesses and atomization rates. I also brushed a test piece. All test pieces exhibited fine checking/spiderwebbing to varying degrees. The thinner the finish, the finer the checking/spiderwebbing. I thought with a water based finish you should spray a fairly wet finish and that it would appear sort of rough and then lay out flat. Is this correct? I have attached some pictures below. Anybody ever seen anything like this or know how to fix it? Could it be a bad batch of lacquer?

Maybe I should just keep spraying and call it my "vintage" finish.

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Aaron Craig

Aaron,
I have experienced exactly the same thing with the StewMac waterbased finish. The only thing I can tell you for sure is to completly strip off all the finish, otherwise you will never get rid of the crazing. Having said that --- I have driven myself crazy trying to figure out what happened on the 4 tenor ukes that I finished this last year. The build before the uke was a D-18 and the StewMac waterbase lacquer worked like a charm. Here are the possibilities that I have come up with:
1. Sprayed the layers too thick. (Don't think so. Why didn't the D-18 give me troubles with the same spraying technique and why did the 3 Koa ukes craze so much more than the Bubinga uke?
2. Bad batch of finish. (Possibly)
3. Bad chemical reaction with the shellac that was used as a wash coat. (This very well could be because I did not use shellac on the D-18. However, on the ukues I used dewaxed shellac flakes from LMI which is supposed to be OK.
4. Some kind of chemical reaction to Koa wood itself. When I talked to Tim Metcalf he said the only crazing that he can remember in a 150 or so guitars finished with Target Coatings waterbased finishes was on a Koa guitar.
So there you go. Hope you can get some answers.
Bill

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Formerly know as Mandodiddle.

Thanks for the info Bill. It has been a very frustrating experience to say the least. I have sanded off most of the finish but I am hesitant to spray again. I did use dewaxed shellac as a wash coat to help adhesion between the z-poxy and lacquer. So how did you end up fixing the koa ukes? Did you reshoot the colortone?

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Aaron Craig

Aaron,
My suggestion is to sand off all (and I mean all) of the finish. Even get rid off the shellac washcoat. I resprayed dozens of times over a 4 month period (This is after multiple sandings to just try and get rid of the visible crazing) and still have some crazing. Also, I would recommend not using the shellac at all. Checking the viscosity of your lacquer with a Ford viscosity cup and checking the thickness of the layers you are spraying with a mil gauge might be of help as well.
Bill

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Formerly know as Mandodiddle.

Thanks for the response. I will take your advice and sand some more before trying to respray. I can't believe you had to respray dozens of times. And I thought I was frustrated.

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Aaron Craig

There was a thread with similar problems a while back. I believe the finish manufacturer told them to add some retarder.

One of many reasons I don't use waterborne finishes.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

I have some retarder on the way. I wish that I could spray nitro, but it will be a while before I get a proper fan. Any other suggestions on a good, non-exploding finish that can be sprayed? I just spent a chunk of change on the equipment and built a booth, and I want to get some practice spraying. I suppose if I keep shoot what I have, I could get lots of extra practice spraying. I have the environment in the booth regulated to the exact "ideal" specs set forth on the Colortone directions, and I shouldn't have to use retarder. I am quickly seeing why so many HATE waterbase lacquer.

Thanks for the advice.

Aaron

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Aaron Craig

Oil based Varnish. It's flammable, but not explosive like Nitro.
The guitar in this picture was finished with oil based varnish.
http://brackettinstruments.com/8Fundamental.JPG

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Thanks Woody. I have been curious about oil varnish, but didn't know if I could spray it safely. I know Laurent uses Epifanes and I like his results. The guitar in your link also looks fantastic. What brand do you use? Thanks for the info.

Aaron

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Aaron Craig

I use Sherwin Williams fast dry oil varnish. I've used Epifanes too. Epifanes dries alot slower. You can re coat the SW quicker (3 to 4 hours in a perfect world). It also dries to a dust free state sooner. I use ~6 coats for a final film thickness of 3 to 4 mils. (.003" to .004")

SW has a slight amber tint, but not quite as much as Epifanes. Behlens Rockhard is a darker amber than SW or Epifanes.

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I didn't mean to say it, but I meant what I said.
http://www.brackettinstruments.com/

Thanks again Woody. I might just give that a try. I like the quick drying time as I can't seem to keep dust off anything in the shop for very long. I also really like the amber color oil varnishes provide. Finished my first with TruOil. Liked the color and feel, but it does not wear well. The guitar already looks like its been played for a few years, and its just a few months old. Sounds good though. Thanks.

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Aaron Craig

I would have my doubts about "flammable but not explosive"
Check the MSDS for whatever you are using, but I know for example that rockhard contains " Solvent naphtha (petroleum) medium aliphatic 41-50%" Basically lighter fluid I believe.
Thats why they also say "Use spark-proof tools and explosion-proof equipment"
Oil varnishes may not be explosive, but their vapours can be very much so.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.