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Im french polishing a classical and have noticed some crazing appearing along the centre of the back. I understand the most likely cause of this is adding layers of shellac without letting previous layers dry and/or not pressing hard enough with the pad to amalgamate the new shellac with old layers.

My question is, do I have to sand back and start again or do I just sand out until crazing disappears.

TIA for answers/comments.

Cheers Martin

Martin - I've never had the problem and don't have enough experience to give a believable answer, but ... Are you just putting too much on? (i.e., too thick a layer of finish?)

I struggle myself with knowing when to quit, and I think the finishes on the first two that I did are probably thicker than they need to be.

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Jim Kirby
kirby@udel.edu

What kind of oil are you using?  I've had that problem before when I used walnut oil that was not as fresh as it should have been.  Seems like the hardening type of oil and the shellac can shrink/dry at a different rate and cause crazing.  I'm back to using olive oil now...

Dave

Hi Martin,
             I think it's an oil issue also .Maybe it hasn't been spirited off enough , or you have used too much .
I prefer to use no oil . Takes a bit longer , but there's nothing to contaminate the shellac . Oil (may )also darken the finish and cause crazy cracking over time.
   
Cheers Craig

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CRAIG LAWRENCE of AUSTRALIA
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The problem is not allowing enough time between glaze sessions.....too impatient.

The oil is olive oil with no additives and its fresh.

Ive sanded back until the crazing is no longer visible and tomorrow Ill pad on more shellac but wait an hour or too between sessions.

Thanks for the comments/answers chaps. Ive been planning to eventually cut out using oil so maybe now is a good time to do so.

I am assuming the Olive oil is Extra Virgin. Ok lets say the oil is not the issue.

I can think of Three thing that come to mind that can cause grazing in FP finish done with wax free shellac out side of bad oil.

Bad shellac

Too fast of a build up during boding without good cure times between sessions

Contaminate on the pad or the guitar.


If it is not contaminate you can do some high alcohol spiriting off till you have melted down past the crazing. Once at a good film continue on but mix a new batch of shellac buy new oil make new muneca. Have many outer covers available. make a new inner pad saturated with your new shellac mix and store overnight in a air tight container. You want to eliminate all possibilities prior to continuing on.

One issue, not so much that has to do with this problem but could, is; I have seen many people FPing with the same outer pad for 5,6,7 and more sessions.

I change outer pad as soon as it starts to discolor (look dirty) and or any sign of lint, dust or anything else adhering to it.

Also I store it in a ziplock bag between each session. making sure to zip it closed when I put it in and take it out.

There is a point in the life of the outer pad that it works the best. For me it is after the second session. Then there is a point where it declines in its ability to transfer shellac and seems to require reloading more often. This seems to correlate pretty close to where the cover is appearing to be a bit dirty.

Change your outer pads when the transfer seems to have slowed will also help to reduce the chances of introducing contaminates.

Interestingly, Eugene Clark, one of the masters of FP, says to put as much walnut oil in as the FP will take...It therefor becomes a French polished varnish...

A lot of FP folks swear by walnut oil, and I've seen some great results with it (and have had some great results myself).  It really can become more of a varnish than just shellac.  After a couple of bad experiences, I retreated to the old familiar olive oil though. 

But heck, I'm a banjo maker, so what do you expect!



Dave

[QUOTE=ballbanjos] But heck, I'm a banjo maker, so what do you expect!Dave
[/QUOTE]


I needed a laugh

More Brasso in the French Polish?  

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Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Thanks again for the assistance on this matter. Im now thinking the pad may be the problem...I do tend to get quite a few miles out of my pad covers.

Rick, I have read about Eugene Clarke's use of oil. At the same time I read of Cyndy Burton and others not using any oil at all.

Michael I think I'll play safe and follow your advice and change oil, shellac and pad covers.

Will let you know how I go with the remedial work.