Cracking Lacquer ???

[Robert Freemond]

Just finished my 1st Lacquer job after numerous KTM's (with mixed results). It was on a rework of an older practice guitar so I wasn't that worried if it didn't pan out. I was so pleased at how it went on that I thought this might be my new approach. It's been curing for about 3 weeks now & the finish is starting to crack - mostly around the bridge & sound hole.
I used Mohawk Per Catalyzed gloss, multi coats at one hour intervals. with a base of shellack.
Any clues as to what I might have done wrong.

[Clay Schaeffer]

Sometimes finishes will crack if they are too thick. Precat lacquers are generally high build so you only need a couple of coats. Furniture lacquer often doesn't have the plasticizers instrument lacquers have, and thicker pieces of wood don't move as quickly with humidity swings as thinner pieces used in instrument making do.
Keeping the finish thin might help.

[Robert Freemond]

Hi Clay, Sounds right what you say. I probably put on way too many coats.
I did however, learn that spray cans can work fine. Do you have a brand you prefer.

Thanks for your response.

[Stephen Neal Saqui]

Sand in between coats. Try out different fillers to apply in between coats. There should be conversations here about fillers. The idea is to keep the finish thin while plugging up the holes.

[Barry Daniels]

Filler between coats??? Never heard of this.

I fill up small holes with "drop fills" of the finish. No worries about incompatible reactions or adhesion problems.

Robert, I think your conclusion that spray cans work fine may be a bit premature. I have heard of many having problems similar to yours.

[Robert Freemond]

Berry, Even with instruments grade lacquers ?

[Barry Daniels]

Yeah, they don't have a good record. I am not saying it can't be done. But, your experience was not successful, was it? I think it is difficult to say what went wrong. Too many coats; too quickly applied coats; wrong type of finish; spray can application? Who knows. You would have to do extensive testing, and it may turn out to be a combination of factors. I am just saying that it is difficult to blame one factor at this point and ignore all the other possibilities.

And I stand by my claim that spray can lacquer does not have a good record of success.

[Robert Freemond]

I'll Take your word for it - & keep testing on other things.

....Thanks