French Polish--again

[Zen]

Hi Guys, I decided to French polish the top of my acoustic dreadnought thats almost completed apart from adding the bridge etc. So, after applying what I though was about 20 coats over the course of 2 weeks and carefully sanding between coats etc etc I have what looks like a lovely finish to me anyway. But, I'm a little concerned after lifting up the tape that I had put down where the bridge is going to be, to find that the final finish is extremely thin. In other words its very thin compared to what I have seen on guitars that would have been finished in nitro. So now I'm faced with the decision on whether to apply more coats to build a thicker layer or leave well enough alone as it looks good right now .Anyone else ever find themselves facing this dilemma ?
Thanks
Rusty

[johnnparchem]

Shellac is a thin. What is a coat in your terminology? When I do FP I talk sessions which puts bunches of layers on. I never sand unless I messed up the FP. So two things, with FP it as easy to take shellac off the top as it is to put it on. Also you do not need to sand between coats or session or ever.

Shellac is a thinner finish than nitro. if it looks good, you probably are good.

[Zen]

Thanks for reply John, So you don't level sand at all ? I probably did 8-10-sessions and polishing twice around the guitar during each session. I level sanded--wet sanded- before the final 2 coats were applied and spirited off the final finish with alcohol . I am waiting for it to harden properly or cure, before attempting to polish the final finish.
How many sessions would you advise
Thanks again
Rusty

[johnnparchem]

I am never sure how many, I go until it looks good and or my arm is falling off. You numbers look good to me. If you are done level sanding and it still looks good it should be OK. If after a few days it looks thin add some more. That is the beauty of shellac.

For a session I start out with a charged pad, not dripping but wet. I apply with the grain until I feel a tack, I put a drop of oil on the pad and use circular patterns around the entire surface I am finishing. I do this until the pad is relatively dry. I increase the pressure as the pad is drying. I finish with with the grain strokes gliding on and off the surface.

I will do four or so of these and then spirit off with alcohol only. When I spirit off again I start wet but not dripping. I go only with the grain. I continue until the pad drys out constantly increasing the pressure of my polishing. When I am finished leveling off the surface is smooth and level.

I will repeat the complete above process 3 - 4 times. So I do about 12-16 sessions.

I might do 2 or three final spiriting off session as described above to finish the FP. I never sand but after a week or so I will buff.

[Zen]

Thanks for that John, Sounds similar to what I have done on this one.
Just one last question-do you ever use pumice on the top as a filler ? If I wanted to be really picky about it I notice one or two tiny pin holes around the purfling and if I did do any more work it would be to try get them filled, although they can hardly be seen with the naked eye but I know they are there.
Thanks again
Rusty

[B. Howard]

My FP finishes are almost always in the 2-3 mill range. That is the beauty of FP, that it is so much thinner than any other finish. That is why I believe they sound a little clearer. I do not count sessions or anything., simply polish until it is done. Sounds like yours is about right.

[johnnparchem]

I have pore filled with pumice and shellac. I have used it to fill pores I found late into the FP. I have not done it at the end. So after I used it there were more build sessions and spiriting off sessions to go. While the pumice does clear with alcohol and provides some fill keep in mind that it is an abrasive, not a filler. When used to fill pores before starting the build sessions, the pores are also being filled with the wood slurry produced by the pumice's abrasive action and shellac.

[B. Howard]

You can fill those small holes with the same "jelly Drop" method as is done with lacquer. Put out a bit of shellac on the back of a business card or something and let it start to dry, stir it a bit as it does and it will thicken up. After ti thickens a bit to about the constancy of honey place a drop on the hole. you will need to let this dry thoroughly for several days and then it can be scraped and gently sanded flush and polished out. I use olive oil for the lube with my wet/dry paper when doing this.

[Zen]

Sounds good Brian !! I will try that. I'm still a little concerned about the dept of finish I have on there as its barely 1mm despite about 10 sessions or maybe more. It looks great otherwise and I wonder if "leaving well enough alone" would be best in this case . I say 1mm as thats what I see when i lift the blue tape that I put down where the bridge is going to go, although its possible I may not have applied as much polish around that area as around the edges and centre

[MaineGeezer]

If it is truly 1mm, that sounds quite thick to me. Nearly 0.04". Not that I know much of anything about finishing a guitar, but I'd guess you want more in the range of 0.1mm, or 0.004".

I assume you'll do a top coat or two of paste was to be the "wear layer." Be sure you are for certain done applying shellac before waxing though, as you can't put shellac over wax without first totally stripping the wax.

Years ago, pre-polyurethane, shellac and wax was the preferred finish for hardwood floors, so we may not be giving shellac sufficient credit for toughness.

Incidentally, I would welcome any information about French polishing that anyone can supply. I'm planning to finish my guitar that way. I've done some French polishing, but I'm not particularly confident that I know what I'm doing.