Speeding shellac cure

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NorCalluthier

Posts: 136
Joined: Apr. 16 2016

Speeding shellac cure

Hello All,

In my quest for a clear pore filler I have tried a dozen or more products over the last twenty years. For various reasons I'm all the way back to shellac itself. Being a solvent based finish it shrinks for a long time, and all the pores begin to show after a few months.

Does anyone have any experience speeding up the "curing" process? I pre-fill parts, and am thinking of using a drying cabinet with modest heat and some air circulation.

Cheers,

Brian

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 7 2019 17:09:53

JasonM

Posts: 2055
Joined: Dec. 8 2005
From: Baltimore

RE: Speeding shellac cure (in reply to NorCalluthier)

Hello Mr Burns, have you ever experimented with adding acetone to shellac to speed up the process? There is a thread on this very subject and pore filling over at the delcamp forum:

https://www.classicalguitardelcamp.com/viewtopic.php?t=86971

I’ve been thinking of doing some test myself with acetone. Wether or not it speeds up the long term cure process or not, I’m not sure I need to read through that thread again. But it does make a difference in fast dry times. I may try it this week

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 8 2019 16:40:23

NorCalluthier

Posts: 136
Joined: Apr. 16 2016

RE: Speeding shellac cure (in reply to NorCalluthier)

Hello Jason,

I started using acetone as a shellac thinner perhaps a dozen years ago. I even bought a fancy micrometer to track shrinkage---I love to play "boy scientist". It turned out to be tricky to get accurate measurements, so I've not continued the experiment.

Email me at:

Brian@BrianBurnsGuitars.com

and I'll send you a .pdf copy of my French polishing notes, which include my experience with using acetone. The offer is good for anyone else that'a interested as well.

Acetone, by the way, is relatively safe and non-toxic. Al Carruth says it's "mother's milk compared to lacquer thinner". I went to three different MSDS sites to confirm this.

Cheers,

Brian

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 8 2019 17:07:57

Tom Blackshear

Posts: 2304
Joined: Apr. 15 2008

RE: Speeding shellac cure (in reply to NorCalluthier)

Brian,

Have you tried organic walnut oil mixed with french polish? My understanding is that the oil dries with the finish and makes a harder surface.

It makes for a quicker build up although you might have to finish off with olive oil, then burnish for a better shine.

_____________________________

Tom Blackshear Guitar maker

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 9 2019 2:40:21

NorCalluthier

Posts: 136
Joined: Apr. 16 2016

RE: Speeding shellac cure (in reply to Tom Blackshear)

Hello Tom,

I'm very familiar with Gene Clark's walnut oil and shellac French polishing. He told me a few years ago that his finish "stayed tender" for up to a year.

My experience is that the addition of any oil---vegetable or mineral---slows down the curing process of shellac. Gene did claim that the shellac plus walnut oil combination ended you up with a more durable finish, that "got rid of the noise".

My experience is that oil in finishes increases the damping and kills treble---good for violins and steel string guitars---bad for nylon string instruments.

My next experiment will be 4 pound cut shellac that has been diluted to 2 pound cut with acetone. This is just to fill the pores---probably several coats, and lots of drying time.

I then French polish with 2 pound cut thinned 2:1 with acetone---around .6 pound cut. That extremely thin mix dries to the touch in about 30 seconds. Paradoxically you get faster build the thinner you go.

I'm determined to come up with a clear pore filler that doesn't decrease treble response, and doesn't shrink in a few months to show the pores again.

Cypress guitars,God bless 'em, don't have the pore filling problem. I use rosewood bridges, head facings, and bindings, but on a blanca they look fine, left unfilled.

Cheers,

Brian

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 10 2019 16:46:06

Tom Blackshear

Posts: 2304
Joined: Apr. 15 2008

RE: Speeding shellac cure (in reply to NorCalluthier)

Brian,

Thanks for your input, I'm always interested in new techniques, even though I grow older by the minute :-)

Let me know how it works for you.

_____________________________

Tom Blackshear Guitar maker

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 10 2019 18:10:34

NorCalluthier

Posts: 136
Joined: Apr. 16 2016

RE: Speeding shellac cure (in reply to Tom Blackshear)

Hello again Tom,

One other thing I should mention is that I have resurrected a closed and heated "drying cabinet" that I made perhaps 25 years ago. It's got a couple of 200 watt bulbs in it that are controlled by a light dimmer. It also has a little fan to circulate the air, and bring in a bit of fresh air from the shop. I'll adjust it to perhaps 100 degrees F. and cycle shellacked parts through it.

"even though I grow older by the minute"---That's the plan isn't it? I have my 80th birthday coming up in February, and I'm still in the shop working 6-1/2 days a week.

Personal aside: I chided you at a Guild convention back in the 1990's about being a Republican. I too am now a conservative, though having left South Texas for California when I was 15, it took me a few extra years to come around (;->)...

Cheers,

Brian

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 12 2019 17:47:15

Tom Blackshear

Posts: 2304
Joined: Apr. 15 2008

RE: Speeding shellac cure (in reply to NorCalluthier)

Brian, you are a funny guy.

Remember the old James Taylor song.............

I love everybody..........

_____________________________

Tom Blackshear Guitar maker

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 12 2019 21:30:46

Tom Blackshear

Posts: 2304
Joined: Apr. 15 2008

RE: Speeding shellac cure (in reply to Tom Blackshear)

Brian,

After the joking subsides I'm serious to know the outcome of your experiment with the shellac finish.

I'm always looking for a better way to do things, Amigo.

_____________________________

Tom Blackshear Guitar maker

REPORT THIS POST AS INAPPROPRIATE | Date Dec. 17 2019 17:12:46