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Archtop Guitar No 4


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I'll include a mini tutorial on the whole french polish process.

That would really be great!

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  • 4 weeks later...

French Polish Tutorial Part 1.

Ok, so French Polish is a technique for applying finish. While there are a few options for finishes that can be applied that way, I'm using shellac.

Materials:

Danish oil

Shellac flake

Ethanol

Olive oil

Ground pumice stone

Cotton balls

Cotton fabric (old t-shirts)

400 and 800 grit wet/dry sandpaper

I mixed up a 2lb cut of very light blonde shellac. This means 2 lbs of shellac flake dissolved in 1 gallon of alcohol. I mixed up only 16 oz/0.5 L so I used only 53 g of shellac flake for this.

First I applied Danish oil. I did this as one flood coat and a second where I used 400 grit wet/dry sandpaper to wet sand the surface. While this made the surface smoother, part of the idea was to partially fill the pores. I don't believe this really did much if anything to fill the pores.

I then let this dry for 72 hours as per Watco's directions. At this point I applied a flood coat of shellac. The purpose of this coat is to lay down enough shellac for pore filling. I just applied it with some folded cotton fabric.

Pore filling is done by using a fresh pad made up of cotton balls inside of a cotton fabric pouch made with a piece of fabric and held into a ball with an elastic band. Only alcohol is applied to the pad along with a very small amount of pumice. This is rubbed on the shellac and causes the shellac to partially dissolve and then this along with the sanding action of the pumice stone creates a wood fibre/pumice/shellac slurry that fills the pores. This process is done over the open pored wood - in this case it is the walnut, Bloodwood and mahogany. Three sessions over the entire surface got me to where I was happy with the filling of the pores.

Here's a couple of shots of pore filling:

Open pores in walnut:

562EC883-423D-4383-B31C-184EEFF06720_zps

Surface after one of the sessions:

382F1C6A-EBB1-4A6C-A189-CE5AC39ABB7E_zps

BEB8C4AA-967F-4E90-95FA-315DADF6A42F_zps

Trying to show the change to the surface:

4455AE6A-32A6-4D0D-8D73-6755CDC191B5_zps

I think this shows pores being filled:

51C843CD-6FB1-4FDA-8447-3A84E0B6F77A_zps

Once this is done I move on to the "bodying" sessions. This is building up the shellac finish and hopefully doing it while keeping it level. For this a new pad is made the same as before but the cotton ball centre is soaked with 2lb cut shellac. About 6 drops of alcohol are added to this followed by one drop of olive oil. I tap this on the back of my hand to spread the oil over the pad. This is then rubbed on the surface in small circles and quickly enough to keep the pad from sticking. You can see the finish get cloudy where the fresh shellac is being applied and it dries back to clear rather quickly. I do one surface entirely before moving on to the next (back, sides and top). As the pad dries/runs out of finish, I add more shellac, alcohol and oil to the pad and keep going. I do this three times before "stiffing". Stiffing is applying only alcohol to the pad and running it in long strokes over the finish. This does two things - removes the olive oil and levels the finish a little bit. Once this is done I let the finish dry 2-3 hours before another session.

This is where I'm at now - 2 bodying sessions complete. I'll do a few more before I wet sand the shellac flat and continue building up the finish prior to the final polishing.

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3D980906-11D5-4C9A-9387-04B1ADD47771_zps

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Scott,

There are a few options for the oil that I've seen. There are two options initially - drying or non-drying oils. For French polishing olive oil and mineral oil seem to be the two most common choices for non-drying oils. Olive oil is usually stated as being the most common, but there shouldn't be much difference between the two. I have a lot of olive oil on hand and I am out of mineral oil right now, so I made my choice based on that. These oils wind up being completely removed between sessions by "stiffing" the finish with an alcohol soaked pad.

As far as I've researched, drying oils such as walnut oil can be used for French polishing, but these oils are incorporated into the film and change the properties slightly. It may be something to experiment with in the future. I've read that walnut oil results in a film that is less brittle and can achieve a higher gloss.

To me the backside of this guitar is the best looking part.

I did the first finish levelling. The process I'm following uses olive oil for wet sanding with 400 grit. I've only used water with added dish soap for wet sanding before and the oil makes a tremendous difference. The paper doesn't clog nearly as much, though the sanding action is much slower... not necessarily a bad thing.

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So long as all of the oil was removed I imagine it should be compatible with most finishes. I think that getting all of the oil removed could prove to be difficult and cause potential problems with the finish adhering. This might prove to quite a hassle. I really don't think there would be enough of a benefit to outweigh the drawbacks.

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I was thinking the same thing.....but I rarely do any wet sanding until after all the finish is applied (read lacquer has all been sprayed) so in that case the drawbacks may not exist......except perhaps for the smell. I could see an urge to keep some crushed garlic and Parmesan close by. These days I rarely wet sand though. I hate the idea of getting any wetting agent on any unsealed areas. Dry micro mesh does it for me.

I had not run across the use of olive oil in any of my French Polishing research (Flexner's book pretty much sums it up).

To me the backside of this guitar is the best looking part.

The back side is gorgeous no doubt. I am probably even more impressed by the creative design features visible from the front though. The sound holes and cutaway and the binding and purfling that highlites them really excite me. And I normally am not a huge fan of excessive decoration.

Good stuff.

SR

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I've gone primarily with the Milburn French Polishing tutorial, which seems to be pretty heavily referenced and he advises the extra virgin olive oil as there's no chance of inadvertent additives affecting the finish.

http://api.ning.com/files/fBYtwDmBUnDWf0sjTN8aZ7yQRhFYxNmpqZRsrDGLjGOtxW3Dg-7kHFIzPIT04SrI350qBJ3vUmdlkRs0tBbJfhiX7FNzTiQo/HowToFrenchPolishClassicalGuitars.docx

I'm going to be keeping this sound hole design as my standard "modern" archtop. I'm very happy with it.

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  • 2 years later...

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