Official Luthiers Forum!

I always think of FP as the 'zen' finish; it's all about awareness and going with the flow. I agree with Bob that the most reliable way to deal with that sort of problem, and many others in FP, is simply to wait a while. I used to get those bare spots all the time, but as I developed my technique I had less trouble with them.

There may be another aspect to this. My dad's old chemistry handbook from his college days lists about 10-12 pages of formulas for denaturing alcohol. Some of them contain things like nicotine, and one uses shellac. There are a few that call for gasoline, or related stuff. Back when I was starting out I was using hardware store denatured alcohol, and sometimes there seemed to be a solvent that would linger for a while, producing a surface that stayed sticky. These were the times I had the most trouble with bare spots, so I wonder if there was not some sort of oil in the denaturant that got into the wood and caused adhesion issues. trying to build up faster with repeated coats often just enlarged the problem area. If I allowed it to sit for a day or so the problems would often resolve themselves, but it did take some time.

One thing I've been doing that helps to speed things up is sort of counter intuitive; I thin out my 2# cut of shellac about 2:1 with acetone. That's two volumes of acetone to one of 2# cut. This is, of course, water thin, so it takes a lot of coats to build, but it dries out so fast you can put more coats on very quickly. Acetone is not as nasty as it smells, since you do have enzymes to deal with it as a normal by-product of fat metabolism. It's still nasty, though, and you sure want good ventilation when you're using it. As you do with alcohol...

Alan, thanks for the tip about acetone. I never would have thought to dilute it so much! But I see the wisdom of being able to put it on fast that way.

Also, it is interesting to think about the denaturing as being An x factor. I never really thought about it that way. I always used everclear but when I switched to Royal-lac, I also switched to DNA because it didn’t make much sense to spend on everclear if the shellac has DNA in it. I wonder how much of the difference I notice in Royal-lac compared to regular is the unknown denaturants.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.

Although Royal Lac and Seal Lac are made with denatured alcohol, I pay the extra money to use Everclear for any alcohol needs of my own, like thinning or cleanup. It’s just sooooo much nicer to deal with, and there is less need to worry about something funky messing with the shellac.

I do the same and for the same reasons.

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Steve Smith
"Music is what feelings sound like"

I like the Zen concept of FP finish. You really do have to live in the moment.

I still use Everclear with Royal Lac too.

My how times have changed as I have aged. The last time I felt this much everclear peer pressure, it was not nearly so healthy.

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Bryan Bear PMoMC

Take care of your feet, and your feet will take care of you.