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| Author: | Pat Hawley [ Sun May 16, 2010 11:03 am ] |
| Post subject: | Splotchy French Polish |
When I just finish a session of French polishing it looks great. Then after about two hours it looks splotchy. I have assumed that it was due to oil coming to the surface and have minimized the amount of oil I have been putting on the muneca. Can anyone tell me what is causing this? It does seem to go away when I polish it up with menzerna, but I would prefer to avoid this if it is possible. Thanks, Pat |
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| Author: | WaddyThomson [ Sun May 16, 2010 8:47 pm ] |
| Post subject: | Re: Splotchy French Polish |
Stiffing off after every body session will cut down on this. Only use alcohol when stiffing off. It will also improve the leveling of the surface. |
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| Author: | BruceHerrmann [ Mon May 17, 2010 2:38 pm ] |
| Post subject: | Re: Splotchy French Polish |
Pat, not sure if this has anything to do with it but I learned from Michael that the extra virgin olive oils are a problem now. They are so contaminated in the pressing process that they can affect your shellac. I switched to 99% pure walnut oil with good success. But your problem may be the stiffing process that Waddy mentioned, it does deal with extra oil very well. My experience is that oil is usually the cause of your problem. Use only as much as necessary, that helps as well... |
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| Author: | Pat Hawley [ Mon May 17, 2010 3:21 pm ] |
| Post subject: | Re: Splotchy French Polish |
Thanks. I'm now down to using no oil and it seems to be getting better. Intersting comment about the olive oil (which is what I have been using). I just watched a youtube video of a fellow French polishing and he litterally puts drops of oil around the top of his guitar and then spreads it out with his fingers and then starts applying the shellac. He seems to be getting good results but I don't know how he gets rid of all that oil. Pat |
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| Author: | WaddyThomson [ Mon May 17, 2010 4:05 pm ] |
| Post subject: | Re: Splotchy French Polish |
I'm of the school that says less oil is better. One person who made a post on another forum, suggests putting a drop of oil in your extra hand, rubbing it around then patting the muneca on it so only a small amount actually transfers to the muneca. I usually only add a tiny drop and spread it around with my finger, then immediately pat it on a piece of paper towel, which removes most of. The next two passes are only shellac, alcohol and residual oil, unless I'm experiencing grabbing. |
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| Author: | Jody [ Tue May 18, 2010 5:13 am ] |
| Post subject: | Re: Splotchy French Polish |
Ervin says in the chapter of his book about french polishing that some oils actualy dry , ( and some dont, or take much lomger ) he reccomends unprocessed walnut oil , which I used on my first and it came out well. the only issue I had was with using masking tape on the bridge... but that is another thread. Jody Pat Hawley wrote: Thanks. I'm now down to using no oil and it seems to be getting better. Intersting comment about the olive oil (which is what I have been using).
I just watched a youtube video of a fellow French polishing and he litterally puts drops of oil around the top of his guitar and then spreads it out with his fingers and then starts applying the shellac. He seems to be getting good results but I don't know how he gets rid of all that oil. Pat |
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| Author: | Chris Beebe [ Tue May 18, 2010 11:50 am ] |
| Post subject: | Re: Splotchy French Polish |
What was the humidity level like? French polishing in high humidity can trap moisture under the finish which turns cloudy white a day or two later. |
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| Author: | JohnAbercrombie [ Tue May 18, 2010 11:59 am ] |
| Post subject: | Re: Splotchy French Polish |
I've gotten into the 'too much oil' problem with walnut oil, though perhaps it would have hardened up over time. (Finish was soft and I was 'pushing it around' rather than building.) I stripped off the finish and started again, trying to minimize the oil use. It worked better. (BTW, on the 'second crack' on that guitar, I sprayed a couple of coats of shellac with a Preval sprayer to 'get things going', as I was pressed for time. It seemed to work out OK.) So, walnut oil may be better than olive oil, but no panacea. Cheers John |
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| Author: | JohnAbercrombie [ Tue May 18, 2010 12:02 pm ] |
| Post subject: | Re: Splotchy French Polish |
Chris brings up a good point about weather/environment, I think. Techniques which will work at 100 deg F in Spain (or Brazil) aren't the same in a 65 deg F basement workshop. I think I read that Eugene Clark uses some 150W floodlights and warm shop to crank the temp up for FP? Cheers John |
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| Author: | Pat Hawley [ Tue May 18, 2010 12:48 pm ] |
| Post subject: | Re: Splotchy French Polish |
The humidity level in my basement is currently around 50%. I've reached the point where I'm using very thin cuts of shellac and not oil and it's looking pretty good. Pat |
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| Author: | Michael Dale Payne [ Tue May 18, 2010 3:56 pm ] |
| Post subject: | Re: Splotchy French Polish |
I don't know exactly what you mean by Splotchy? If you mean Whitish cloud; That is moisture intrapment. If you mean lumpy, pitted or dimples: that indicates wornout outer cover, sticking or stopping on the surface, and or other contamination. If you mean that there are uncoverd areas; then that is a consistancy of and control issue of your bodying stroke. You should start in the middle of the body and work towards the edge in a consistantly over lapping motion. over lapping by 1/2 the muneca as you move forward. You confuse me some with saying you at the point of using lighter cut of shellac. You should use 2lb untill you have reached total film thickness. you do not switch to 1lb till you are ready to glaze (burnish the outer surface of the film to achive desired gloss) All bodying (building film thickness) is done with 2lb cut I suggest spiriting-off after every body session is critical to building a level thickness as you body. Also avoid going back over previously covered areas with in a single session. [A session is one complete coverage of the surface] doubleing back over areas tend to push shellac away from that area when done within a single body session. There need to be time for the newly bodyed shellac to touch dry before spiriting-off and then again time for the newly spirited-off shellac to touch dry before the next body sessions begins Yes I did say that you need to watch out when using Extra Virgin Olive oil. Some unreputable vendors are using presses that have been used to press other than just the meat of the olive in (ie twigs and leafs are included in the pressed mixture. This will introduce tanic acid and undesireable oils to the rendering. and thus does not render Extra Virgin Olive oil. Stay away from the cheap brands and the Crisco prodcuts. |
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