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Shellac cure time?
http://www.luthiersforum.com/forum/viewtopic.php?f=10101&t=36389		 Page 1 of 1
Author:  alan stassforth [ Sat May 05, 2012 4:38 pm ]
Post subject:  Shellac cure time?
Anybody out there spraying shellac?
First time for me,
and I like it!
Anyway, got the last coat on today, I think,
and was hoping to polish out next weekend.
I used a 1 lb. cut mix,
wet sanded between most coats with 600,
and will wet sand with 1200, then rottenstone,
then Mequiars # 18 plastic polish,
no buffing.
Author:  Alexandru Marian [ Sat May 05, 2012 6:35 pm ]
Post subject:  Re: Shellac cure time?
French polished shellac can be handled safely in a few hours, played (with care) after 1 day and effectively buffed with rottenstone after 2-3 days. However, If I wait about 1 month the gloss is much better! Overall it remains delicate for a few months and continues to harden for years. I recall Al Carruth said that it takes about 70 years to turn bombproof :D
Being sprayed, I have no idea...but my gut feeling is: play safe and wait as much as you can bear.
Author:  Michael.N. [ Sun May 06, 2012 5:56 am ]
Post subject:  Re: Shellac cure time?
The longer you leave it (within reason) the flatter the finish will end up. Rubbing down after 1 week and it's likely to sink back resulting in a less than flat finish. Not bad in itself, if you like a little texture.
I've never sprayed Shellac (only brushed it) but I suspect it will give a thicker film than French Polishing. In which case you would be better off waiting 3 or 4 weeks for it to cure - that's if you want the super flat finish.
Author:  John Lewis [ Sun May 06, 2012 6:13 am ]
Post subject:  Re: Shellac cure time?
I have a 100+ year old parlor guitar and the shellac finish is hard as a rock and seemingly waterproof. I have a steel string guitar from 2005 and the you can easily scratch or dent the shellac finish. So more than 7 years and less than 100. :D
Author:  WendyW [ Sun May 06, 2012 11:06 am ]
Post subject:  Re: Shellac cure time?
Alan, what did you use to wet sand with? Thanks, Wendy
Author:  alan stassforth [ Sun May 06, 2012 12:04 pm ]
Post subject:  Re: Shellac cure time?
Thanks for the info.
I had a gut feeling that was the case.
Shellac dries really fast, initially,
but stays kind, but not really "sticky".
I polished out my last f.p. job with rottenstone,
and i like the finish on that,
but it sat around for months after the last coat.
Wendy, I used 600 grit wet sanded.
I just did fast sanding sessions to even out the nibs,
and take any orange peel off.
Author:  Andy Birko [ Mon May 07, 2012 8:04 am ]
Post subject:  Re: Shellac cure time?
One tip is to let the coats dry fairly thoroughly before going on to the next one. I believe there's an article on finishing with shellac from about 12 or so years ago in FWW and the tip was to not do too many coats a day as you'll trap solvent in the deeper coats that will take longer to evaporate.

So as usual, go slower to finish faster.
Author:  Tai Fu [ Mon May 07, 2012 11:43 am ]
Post subject:  Re: Shellac cure time?
Honestly I wouldn't rub out/buff a sprayed shellac finish.

I mean get it on thin, and when it cures wet sand it with 600 then french polish (with a very light cut or just alcohol) until you get a good sheen.

The gloss you get from french polishing is almost as good as rotten stone and liquid polish. It takes a few days to get the proper gloss though as you shouldn't build them too fast but the day after and it's ready.

French polish shellac cures faster because you are building very thin finish so there are less solvents trapped under the finish.

The advantage of french polishing the final layer is that should you sand through by accident, you're still safe because the french polish would add more shellac. I might think about spraying the first few coats on in order to seal and build it.
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