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PostPosted: Sun Oct 07, 2018 7:32 pm 
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First name: Wendy
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The best french polish finish I ever did was my first, following the Milburn instructions. I decided to go back to that method and give it another try and I am so frustrated! The neck, peghead, and sides are all done and beautiful. The top and back have been giving me fits and each has it's own unique problem:
The back was pore filled with Robbie O'Brien's rosewood dust and shellac method, which worked really well. All was well until I got to the glazing. The pores have not sunk, they actually look as though they are raised. Believe me it was definitely well sanded. No problems all the way through the bodying sessions. After my glazing sessions today you could feel the pores as if they are raised. I decided to spirit off, thinking maybe it was oil. My pad came away with a dark grayish black coloring on it. What the gaah !!! After glazing yesterday it looked glass smooth. I don't get it, and not sure where to go from here?

The top is a whole different story. Prior to the 2nd leveling I did a couple of drop fills with CA. I scraped them flush and didn't think I sanded too vigorously in those particular areas when leveling, but wanted to make sure I wasn't leaving any raised CA. I didn't think I burned through but I now have some blotchiness in those areas. I didn't notice it until I got to glazing...because you don't see it looking straight at it, or from the side. The only time you can see it is when you look at the soundboard down the neck from the peghead. The only thing I can figure is that I burned through when sanding and the oil has darkened the soundboard where I burned through. Any ideas if I am correct and, if so, how to solve it?

Please no remarks about level sanding with the French polish process. I chose to follow this process this time (probably not again). Just looking for advise on how to solve my problems. TIA, Wendy


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PostPosted: Sun Oct 07, 2018 8:15 pm 
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Koa
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Give Robbie $50. Order the french polish class. Well worth it.

That aside, keep in mind that fp is always repairable. You’ll fix this.

Let it set a day or two. Do something besides guitars (ikr? There’s life besides guitars?!)

Maybe the oil soaked in and swelled the dust of your pore fill.
If it wasn’t totally sealed with shellac before you started the fp process and you introduced oil to those pores, they very well could have swelled up.
I won’t tell you to level sand, but that is EXACTLY what I would be doing with it.

For now, do another session or two over it ans see what happens.

CA probably isn’t the drop fill you want to use. For me it has a tendancy to shrink differently than the finish. Alternative is Crystal lac. Or some other wb filler. It appears to do weird things to the surrounding shellac, but evens out with a little FP. Just be careful not to concentrate your efforts on the blemishes. You can pull the shellac OFF that area and you will end up with blotches.

Good luck

dl


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PostPosted: Sun Oct 07, 2018 9:00 pm 
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I know you said "no remarks about level sanding with the French polish process" but.....

There is nothing wrong with that. In fact it's pretty common to level sand before glazing. I like the 3M polishing papers and always have some on hand for when I get a cat hair or some errant spot of dust in the finish.

FP is an interesting process. Your shop environmental controls has a lot to do with it too. Some days everything works so incredibly well and just when you think you are done you want to touch something up and.... What? What just happened? The pad wants to stick and the same shellac you have been using for weeks is all of a sudden garbage. That's when the fine sanding papers come in.


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PostPosted: Mon Oct 08, 2018 5:27 am 
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I recall a GAL articled in which Richard Brune mentioned leveling with dry sand paper.


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PostPosted: Mon Oct 08, 2018 6:20 am 
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Your process with leveling and drop filling is not FP!!!! There is your first problem. The pores are likely swelling from re-wetting with solvent, they should settle back down and become flat in 48 hours or so in average shop humidity.

How I do it.... https://howardguitars.blogspot.com/2015/09/french-polish-finishing-traditional-way.html

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These users thanked the author B. Howard for the post: DannyV (Fri Oct 12, 2018 8:07 am)
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PostPosted: Mon Oct 08, 2018 9:18 am 
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If you sand through on a light top you will get blotchy areas. I not sure it is oil. Spruce starts darkening after sanding. If you sand through an area, it will be lighter than the surrounding areas. Also on light top wood, small areas sanded with different grades of sandpaper show up when looked at from different angles. The finish magnifies the difference in surface prep. I have never been happy with anything I have done to spot repair an area on a spruce top where I sanded through. I general work for a couple of days on it and in disgust strip it, very lightly sand and refinish. I never sand the finish off as the top will get too thin.

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PostPosted: Mon Oct 08, 2018 7:03 pm 
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Thanks Dave, I do have Robbie's class and just chose to follow the Milburn method this time. And thanks for reminding me that I will get this fixed.

John, yes this is a very light color Englemann spruce top. The two areas I see when looking at just the right angle are darker than the rest of the top. After reading your post I have decided to go ahead and strip the top, and lightly sand as you suggest, then reseal and restart the french polish process. I'm assuming that to strip I just have to keep wiping with straight Everclear, which is the alcohol I dissolved the shellac flakes in? Or do you have another method of stripping?

jfmckenna, interesting that you mention shop environmental controls. We just went from hot dry desert to cold and rainy. My shop is well controlled but I had to go from A/C and humidifer to now using a dehumidifier that puts out a lot of heat. Maybe...who knows.

Brian, thanks, I plan on watching your video when I have some time this evening. I will also give the back a couple of days and see if the pores go down, but at this point I am considering stripping both top and back. The sides were pore filled with Aqua pore and are having none of the problems that the back is having. The only reason I used sawdust and shellac to fill the back is because i had some pumice turn white in some of the pores on the back. Since they were not completely filled the sawdust fill covered it.

Ironic...I had thought about sending this guitar out to be finished but at the last minute decided to just try and finish one more. I can build beautiful guitars, but always mess up when it comes to finishing.



These users thanked the author WendyW for the post: Dave Livermore (Sat Oct 13, 2018 12:27 pm)
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PostPosted: Mon Oct 08, 2018 9:41 pm 
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The everclear will be tough; if you put enough on and leave it long enough to soften the finish the everclear will drip down the sides. If you are just wiping little by little you will remove some, but not so much. I was too impatient, I went to hardware store and bought some gelled stripper. I taped up the sides to protect, had the neck in a vice so the finished back would not sit in any scraped finish and stripper and I protected the inside of the guitar from any drip from the stripper. With all of that I carefully applied the gelled striper waited 10 minutes and used a scraper to lift the finish off of the top.

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PostPosted: Wed Oct 10, 2018 7:10 am 
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FWIW there are 2 excellent youtube video series on FP by luthiers michael Thames of santa fe NM and stephen Faulk in japan. I learned everything about FP that I needed to know.



These users thanked the author ernie for the post: Pmaj7 (Wed Oct 10, 2018 7:37 pm)
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PostPosted: Wed Oct 10, 2018 10:56 pm 
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John, Did you try the Everclear before you decided to use the stripper? I haven't tried it yet but last night I came across an old Delcamp forum post about removing french polish and the guy said that the finish easily wiped off with Everclear. I think he said he used it with 0000 steel wool. It would sure be nice not to have to use gel stripper.


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PostPosted: Wed Oct 10, 2018 11:08 pm 
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WendyW wrote:
John, Did you try the Everclear before you decided to use the stripper? I haven't tried it yet but last night I came across an old Delcamp forum post about removing french polish and the guy said that the finish easily wiped off with Everclear. I think he said he used it with 0000 steel wool. It would sure be nice not to have to use gel stripper.


Give it a try with the everclear and steel wool, it should soften the finish while rubbing. I have tried alcohol and rags, and I suppose given enough time I could soften and remove the finish. My worry was that I would need to work very wet to dissolve the shellac; so it would be hard to protect the rest of the instrument. I did mask everything so maybe my fear was overblown. The striper gel stayed where I put it. Only the top for me. I came back 10 minutes later and the French polish came off in soft sheets with a dull scraper. When finished I did wipe the top down with alcohol. I ended up with a clean top that still looked freshly sanded.

Edit, I have an old FP top so I gave it a try. Using a rag wet with everclear, rubbing for I while and scraping with a relatively dull straight edge razor blade, I was able to remove layers of soft shellac. Working in a small area I had to repeat this process a 4-5 times before I thought I had wood. I would test with a bit of sanding to see if I got spruce dust or shellac dust. So with a bit of time and work the shellac will work.

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PostPosted: Thu Oct 11, 2018 6:22 am 
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Wendy whenever I wanted to clean off the FP finish , you can buy 91 per cent alcohol from big lots for $2 for 1/2 a quart,. I would use a coarser grade of wet an dry sandpaper e.g 180 or 220 the steel wool leaves all kinds of residue , which requires a lot more cleanup . I flood the surface with alcohol and clean and strip away . If you are using steel wool . I would start with OO better suited for stripping . I started stripping oak floors when I was ten , using paint solvent and O grade steel wool.


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PostPosted: Thu Oct 11, 2018 10:27 am 
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If you saturate paper towels placed on the top with the alcohol they will help it stay where you put it and provide a reservoir to have more solvent in place to work on the shellac. I would allow it to stand on the surface for several minutes, then use a putty knife and green scotch brite to remove the softened finish.


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PostPosted: Thu Oct 11, 2018 6:21 pm 
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John, do you remember what kind of gel stripper you used?


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PostPosted: Thu Oct 11, 2018 9:37 pm 
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I used strypeeze. It is nasty stuff so if you use it use it with ventilation, a mask gloves.

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