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FP Sand between coats?
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=12227		 Page 1 of 1
Author:  Jebarri [ Tue May 29, 2007 9:41 am ]
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Hey,
I just started French Polishing on my first 2 guitars, I got the wash coats on
and did the pore filling.
anyway, my question is, should I sand between coats?
If so what grit sandpaper?
It seems to me you would except since all the layers merge into one does it
matter?
Any info would be helpful.
Author:  Martin Turner [ Tue May 29, 2007 12:07 pm ]
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I sand back every 5 or so body sessions. I use 1200 grit W and D and only sand lightly to remove high spots.

See Robbie Obrien's DVD on finishing for a simple and effective FP technique.

Cheers Martin

Author:  SimonF [ Tue May 29, 2007 12:09 pm ]
Post subject: 
Jebarri,
No need to level between each coat unless you trap some lint or dust,
etc... I do 8 bodying sessions and each session takes me a full 2 hours to
cover both the body and neck. After that, I level with 400 grit sandpaper
and do 4 glazing sessions with a 1 lb cut of shellac. When sanding I use
mineral spirits to help from loading the paper - don't use water!!!

Best of luck,
Simon
Author:  Jebarri [ Tue May 29, 2007 1:21 pm ]
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Thanks Martin and Thomas
I guess I'll level out the wash coats and then go on to bodying.
Author:  Jebarri [ Tue May 29, 2007 1:27 pm ]
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Ooops...
Sorry Simon.... I read the name from your quote...
Author:  Michael Dale Payne [ Wed May 30, 2007 12:05 am ]
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When I French polish I rarely have to level with sand paper because I spirit-off between every session after the second. The spiriting off process melts the high spots there by leveling the film. This takes some practice and attention to what you are doing, but with proficiency and a good spiriting-off technique you will find that sanding to level is not needed or at least rarely needed.
Author:  Colin S [ Wed May 30, 2007 12:37 am ]
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Like Michael, once I start to French polish, no abrasive of any kind is used, neither do I buff out at the end. If sufficient care is taken with the spiriting off and final glazing then the finish should be just that, finished. the correct pressure applied duing spiriting off, I believe, is key in producing a hard even surface.

colin
Author:  Michael Dale Payne [ Wed May 30, 2007 1:24 am ]
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I would like to add some insight here to the FP finish and leveling for those new to French polishing.

First the way you apply the shellac and the way the solvent works in the process; FP technique is a 100% self leveling process. A high quality inner and outer pad will leave almost no ridging unless you are applying too wet or too dry. The application it self levels as you go.

That said there is some micro ridging during "boding" (the application of the film) Notice I do not call these coats be cause coats implies that you are laying one layer over another. In fact in the FP process you are amalgamating sessions into one continuous film.

The Spiriting-off process between boding sessions whole purpose is to melt down any micro ridges left after the previous body session.

unless applied too wet or unless you are having problems sticking while boding, spiriting or glazing there should not be a reason to need to level by sanding the film. The process alone should render a level surface. If you are needing to sand then the technique can be refined to eliminate this need.
Author:  crazymanmichael [ Wed May 30, 2007 1:43 am ]
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like colin and michael, the uncrazy one, i don't use abrasive when french polishing. as they rightly point out, true french polishing is self leveling.

but i think there is a bit of symantic confusion often evidenced here when using the term french polish. when i think of french polishing, it is a specific, defined method of applying shellac to achieve a finish. whilst there are variations in the technique, it always involves the application of the shellac by hand with a pad, sometimes referred to as a fad or munica. the composition of the pad, the timing of applications, variety of oil used as a lubricant, the additions of bodying agents, e.g., pumice, are all valid variations of the technique.

some use it to refer to using shellac in just about any manner. some even use the term as a synonym for shellac. is not french polish.

there are some who talk of rapid or quick bodying by brush or spray applications of shellac. to me this is not french polishing either. this is not to say that the finishes achieved in this manner are inferior, but to me they are not french polish.
Author:  Michael Dale Payne [ Wed May 30, 2007 2:00 am ]
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[QUOTE=crazymanmichael] like colin and michael, the uncrazy one, i don't use abrasive when french polishing. as they rightly point out, true french polishing is self leveling.

but i think there is a bit of symantic confusion often evidenced here when using the term french polish. when i think of french polishing, it is a specific, defined method of applying shellac to achieve a finish. whilst there are variations in the technique, it always involves the application of the shellac by hand with a pad, sometimes referred to as a fad or munica. the composition of the pad, the timing of applications, variety of oil used as a lubricant, the additions of bodying agents, e.g., pumice, are all valid variations of the technique.

some use it to refer to using shellac in just about any manner. some even use the term as a synonym for shellac. is not french polish.

there are some who talk of rapid or quick bodying by brush or spray applications of shellac. to me this is not french polishing either. this is not to say that the finishes achieved in this manner are inferior, but to me they are not french polish.
[/QUOTE]

Well put Michael! by the way I have been known to a bit crazy now and then
Author:  Joel [ Wed May 30, 2007 2:48 pm ]
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Crazy- and Uncrazy-Michael ,


Can you perhaps give us an idea of what you consider to be the correct amount of pressure to use during boding, spiriting and glazing?


I've watched Robbie O'briens DVD (which is excellent), but the only bit I of info I'd like to find more about before I start is how 'hard' to rub.
Author:  crazymanmichael [ Wed May 30, 2007 11:03 pm ]
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is that a schooner of toohey's old i see ????

correct pressure --- it seems to vary with the ambient temperature, how fast you work the fad, how wet the fad is, how much oil you use, etc., and to me is just what works with the shellac mix you have to hand.

you can feel when the section you are working is right, as good as it will get. the shellac almost gives a crack feel, and any further work will only do damage, move on to the next section.

this is a touch skill, and like any other it can only be learned by doing it, a lot. unfortunately no magic shortcuts. but once you experience the feel of the shellac going crack under your hand you won'r forget it, and then it gets down to learning how it feels leading up to that.

similarly with spiriting off. it will feel different if you have let the piece sit too long and your oil has dried a bit too much, or if the the shellac is still too green.

but you always want to go in the same direction, with the grain. and don't stop your stroke on the work, stroke clear off the edge.
Author:  Michael Dale Payne [ Wed May 30, 2007 11:58 pm ]
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[QUOTE=Joel]

Crazy- and Uncrazy-Michael ,


Can you perhaps give us an idea of what you consider to be the correct amount of pressure to use during boding, spiriting and glazing?


I've watched Robbie O'briens DVD (which is excellent), but the only bit I of info I'd like to find more about before I start is how 'hard' to rub.

[/QUOTE]

The other Michael's answer is pretty much on. Humidity, temp and BM pressure all affect the viscosity of the shellac and the surface you are padding it to. I would highly recommend that you experiment on scrap wood a lot before moving on to a guitar. gut FPing a 6 x 6 square will show you a lot and doing it sever times will teach you several times more
Author:  CarltonM [ Thu May 31, 2007 7:12 am ]
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[QUOTE=MichaelP]The Spiriting-off process between boding sessions whole purpose is to melt down any micro ridges left after the previous body session.[/QUOTE]
Michael,

What's on/in your pad when spiriting? Some shellac with extra alcohol? Just alcohol?

As for what pressure to use, as a beginner I've had pretty good results with firm, decisive pressure, but not enough to distort the wood. A good place to start?
Author:  Michael Dale Payne [ Thu May 31, 2007 7:18 am ]
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There is residual shellac in the inner pad. The pad gets charged with about 4 drops of alcohol per load up but no new shellac and one drop of lubricant oil. These strokes are like buffing a shoe with a cloth buffer. in plane with the grain and from on direction only. glide on and glide off in swift but not hard motion. Never letting the motion stop or slow down from one end to the other.
Author:  Joel [ Thu May 31, 2007 8:09 pm ]
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Crazymanmichael,

Toohey's Old??? I think not! That is my own Vienna style lager. I tried to get a picture of a glass at least half full.... but it was just too nice to stop drinking to start playing with the camera. If my guitars turn out half as well as that beer then I'll be a happy man.


But back on topic,

The only other style of polishing I've ever done is spit polishing my service dress shoes during Basic Training (also had to do my GP boots - the whole boot. Military instructors just don't have a sense of humour ). I found that building up a decent foundation took a surprising amount of pressure and elbow grease. And the final gloss 'coat' was quite lightly done in comparison to avoid swirls or scratch marks. Can this experience be equated to FP? If it can then I'm already a pro!

Author:  Michael Dale Payne [ Thu May 31, 2007 11:46 pm ]
Post subject: 
Joel,

Yes some what but the pressure when boding is not that great. There is a good bit of elbow grease required but itis more like applying wax to a car finish during boding and like pop cloth shoe buffing when spiriting off except in a single direction well sorta
Author:  crazymanmichael [ Fri Jun 01, 2007 2:25 am ]
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ah joel, now i am envious!!!! have you been brewing long?

i too had the unenviable experience of spit polishing shoes, and boots, and floors, and desk blotters, arrrgggghhhhh. and we used alcohol as the finishing agent there as well.

but the pressure required to french polish is perhaps not so high. but the finishing is similar in its pressure requirements. but as was posted elsewhere on the thread, it is unidirectional.
Author:  WaddyThomson [ Fri Jun 01, 2007 2:40 am ]
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Hmmm!  Seems many of us have had similar experiences.  I guess I know more than I thought I did.  Seems like brass was an issue too, and I remember the light strokes to remove polish lines in the belt buckles.
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