Official Luthiers Forum!
http://w-ww.luthiersforum.com/forum/

Finishing
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=11385		 Page 1 of 2
Author:  KenH [ Mon Mar 26, 2007 1:14 am ]
Post subject: 



I am about 90% done with my first french polishing job on a guitar. I knew in advance that this was going to be a labor intensive project, but so far this has exceeded all time expectations.


I am pleased with the results so far, but I do have a couple of questions. I guess I should start with what I have done so far and what I have found to work for me:


 


I started with dissolving about 1.5" of blonde shellac flakes (stewmac) in about 4 inches of behkol solvent (stewmac) to make what I would guess to be about a 2 pound cut of shellac. This was in a 1 quart mason jar.


I put the first three coats on rather quickly using a wadded up roll of wool covered with patches of t-shirt material. This was allowed to dry overnight.


next came the pore filling using fffff pumice and behkol solvent. This was done using very little pumice and using small circular strokes until I could literally hear the surface getting smooth. Over the course of several days, I had to repeat this process several times because of spots in the surface of the back that didnt seem to get filled on the first attempt.


I might add that extra virgin olive oil was also used.... sparingly... to help lubricate the muncia while these first two steps were being preformed.


From here on, it has been a learning curve, but I have found a couple of things to watch for and a couple of tips for future use:


 


I had about 4 more sessions of placing coats on using the wool and cotton muncia. The instructions I had acquired said to use small figure eight strokes, but this only seemed to drag up the earlier coats and cause me to have to stop, let it dry, sand off what I had and start over again


I found that using long strokes, going with the grain and starting at one end of the guitar and then going completely off of the guitar on the other end made for better control and a cleaner work surface.


After I had these sessions completed and allowed it to dry overnight, I could use 800 grit sandpaper soaked in olive oil and liberal amounts of olive oil as a lubricant on the surface of the guitar to sand everything smooth and come up with a nice smooth surface.


At this point, I thinned the 2 pound cut by adding 3 parts of behkol to one part of the previous 2 pound cut of shellac. Numerous sessions were had over the next several days.


I found that if I did more than 4 coats to the surface at any one session, the finish would "slip" and cause a nasty spot on the guitar which required fixing and a lot of extra work. The way I started out fixing it was to sand everything off and start over again  but I found an easier way to fix it later. I would sand the bad spot down using the olive oil and 800 grit sandpaper, then using an artists paint brush and very light strokes with the origional 2 pound cut of shellac I could mend the bad spots, let it dry overnight and then sand the whole surface to a "repaired" condition. The repaired section was undistinguishable from the origional when I finished with this process and it saved me from sanding the complete surface off and starting over. I'm not sure if this is being smart or just being lazy, or what the long term results will be, but so far it has worked and looks fine.


 


As of right now, I have about 15 of these last sessions of shellac on the guitar and it shines like glass.


I have ordered a bottle of macguiars #7 and a bottle of #9 to finish off the surfaces.


I have been at this for exactly a week so far, but not working full time on it since there is a lot of the time that I have to stop and wait for the surface to dry before proceeding. I also wasted a lot of time sanding off bad spots.


I have another exact guitar that is using wood sawn from the same billets and built at the same time that I am going to finish with nitrocellulose.... just to see if I can tell if there are any differences in the tonal qualities.


If you have any tips or tricks on french polishing that would help me in the future, I would be more than interested in learning how you do it. If you know of a good method of fixing scratches and chips in a french polished guitar, please post them!


 


Ken Hodges


www.hodgesguitars.com


 


 
Author:  letseatpaste [ Mon Mar 26, 2007 1:33 am ]
Post subject: 
Check out Robbie O'Brien's finishing DVD. I don't actually have it, but I took Marshall Brune's French Polishing class with Robbie, so I learned that method at the same time. It's a whole lot simpler and quicker than other FP methods I've read about.
Author:  Bill Bergman [ Mon Mar 26, 2007 1:48 am ]
Post subject: 
If you have American Lutherie (Journal of the Guild of American Luthiers) Number 79, there is an article by Richard Brune (Marshall's father and teacher)that summarizes his simpler method of French polish. Presently, he fills pores with a more or less off the shelf filler. He polishes with a very thin cut in 190 proof alcohol from the liquour store. No oil added. Of course there are nuances to it.
Author:  SimonF [ Mon Mar 26, 2007 2:19 am ]
Post subject: 
Hi Ken,
I go according to the traditional school of thought regarding French
Polishing. You can check out the Milburn Tutorial on the web - it is an
excellent resource and will give you all the specifics.

That said, here is an overview of what I do. I fill using a finishing resin
epoxy that I get from LMI. I do this over the entire guitar and sand back
to the wood. I repeat 3 times. French polish has a nasty habit of showing
every underlying surface imperfection around the binding/purfling,
rosette, etc... So to get a "perfect" finish you need a perfectly flat surface
to begin with.

I start with a 2lb cut of pale shellac and do 2 sessions per day. I go
according to the Milburn instructions. Each session takes me a full 2
hours. I do 8 sessions total. I wait one full week before leveling with 600
grit sandpaper (I use mineral spirits to wet sand). I then do 4 glazing
sessions with a 1lb cut of shellac.

There is definitely a learning curve involved. You should always start out
seeing a trail behind the muneca after its been loaded. I also highly
recommend you take a very soft cotton material and cut it up into small
circles. Thread these together on top of one another to use for the
bodying sessions. For the glazing sessions, I use Dr. Scholl's lamb's wool
to make for a softer muneca. You also want a lint free material or you
WILL get lint trapped in the surface. I have found that a high quality
cotton men's dress shirt that is well laundered is the absolute best
covering.

I am not familar with the Brune method but I do question whether the
resulting finish is of the same quality as the traditional method. Not all
French Polishes are created equal. It is entirely up to you to get a hard
and compact final finish. In my opinion, the glazing sessions are
extremely important because they serve to harden the finish. If you don't
put much pressure while padding you will end up with a very soft finish.

Call 386 424-0936 if you want a much more detailed run through I what I
do.

Best of luck,
Simon Fay
Author:  Bill Bergman [ Mon Mar 26, 2007 2:59 am ]
Post subject: 
Yes, Brune does the final coats thinner. If I understand correctly, he does this after the main application by gradually adding only alchohol to the pad, so it gets cut thinner. Anyway, I am not an expert. Read the various articles.
Author:  CarltonM [ Mon Mar 26, 2007 6:53 am ]
Post subject: 
[QUOTE=Hodges_Guitars] The instructions I had acquired said to use small figure eight strokes, but this only seemed to drag up the earlier coats and cause me to have to stop, let it dry, sand off what I had and start over again [/QUOTE]
I think it's because of your solvent. Bekhol has additives that slow its drying time. We want the alcohol to flash off quickly, so by the time your pad returns to a spot, it's dry. Just use plain ol' denatured alcohol.

[QUOTE=Hodges_Guitars]I found that using long strokes, going with the grain and starting at one end of the guitar and then going completely off of the guitar on the other end made for better control and a cleaner work surface.[/QUOTE]
That should be done at the end of every session anyway. It smooths out any swirls left behind, and helps to evenly distribute the shellac. That's if you don't do as I have done, and try to put on too heavy of a layer to start.

[QUOTE=Hodges_Guitars]...it shines like glass. I have ordered a bottle of macguiars #7 and a bottle of #9 to finish off the surfaces.[/QUOTE]
If it shines like glass now, why use the polishers? FP isn't supposed to look like a nitrocellulose finish. Its warm glow is what makes it beautiful. If you can clearly read the reflected lettering on a lightbulb, you're good to go!


Author:  KenH [ Mon Mar 26, 2007 9:23 am ]
Post subject: 



I tried the liquor stores locally and 151 proof is the best they had. Looks like next time I attempt this it will have to be with a better solvent. I had suspected the solvent as being a problem from the beginning.


 


To answer another question, although the surface of the guitar is shinging like glass and I can even read a backwards newspaper with it, there are still some spots that could use an extra polishing due to haze or other imperfections. I am hoping that the macguiars will help solve these problems.


 


Thanks for all of the feedback and suggestions!

Author:  JJ Donohue [ Mon Mar 26, 2007 10:14 am ]
Post subject: 
Until I learned from experience what Robbie stresses in his DVD that less is better, I continued to fail at getting a quality finish. It seems to be counterintuitive and I kept using way too much shellac.

I now actually count drops as I add the shellac or ETOH to the muneca. Start long strokes using very light downward force. As you continue moving across the surface and as the shellac becomes depleted, bear down harder. When you think the pad is dry, it isn't. Keep rubbing harder and this is where the effective polishing happens and the surface hardens.

Remember...less is better! Once you get it you'll never forget it!
Author:  KiwiCraig [ Mon Mar 26, 2007 10:17 am ]
Post subject: 

It's important to use circular motions with your pad (rubber ) as well as the long with the grain types .If you don't use the circular motions , you will end up with what's called a "ropey " finish . This is where you will notice fine lines ( ridges ) , following the grain .


     Lawrence of Australia
Author:  Blain [ Mon Mar 26, 2007 10:38 am ]
Post subject: 
Where can you buy the Dr. Scholl's Wool?

I've searched for it in the stores from Home Depot, to Wal-Mart to Fabric stores and Hobby shops, but have had no luck.





Author:  Bill Bergman [ Mon Mar 26, 2007 10:53 am ]
Post subject: 
Dr. Scholl's in the pharmacy. It is used to pad sores on feet.

151 proof is 24.5% water, which is too much for French polish. "Pure" grain alcohol at the liqour store (if they carry it) is actually 95% alcohol (190 proof) and 5% water. This is the percentage that ethanol and water evaporate at once they are mixed together. An ordianary still cannot get rid of the last 5%, hence the long standing custom of calling 190 proof "pure" grain alcohol. There are, of course, industrial ways to get the last 5% water out, but then you have something that might be too dry for optimum use. An earlier thread pointed out that denatured alcohol has various and not consistent denaturaing agents, some of which might be deliterious to the French polish.
Author:  JJ Donohue [ Mon Mar 26, 2007 10:53 am ]
Post subject: 
I use cheese cloth as the inner pad. It has worked well on 4 guitars.
Author:  SimonF [ Mon Mar 26, 2007 10:53 am ]
Post subject: 
Dr. Scholl's Lamb's wool is available from Amazon.

Without a doubt, learning to load the muneca and make small
adjustments is the hardest part. If you go by the "blot test" as described
in the Milburn Tutorial it will guarantee that you will not damage your
finish by putting too much on.

I also strive for a flawless and very high gloss finish. After I complete my
glazing sessions I wait for a few days and then use the Meguiar's. The
resulting finish easily rivales the lacquer finishes I have done by Addam
Stark. I really do love French Polish but it is very time intensive. It is
second nature to me now but it takes me about 22 hours per guitar - not
including the epoxy pore filling.

Peace Out,
Simon

Author:  jhowell [ Mon Mar 26, 2007 11:29 am ]
Post subject: 
Lots of good info in the above posts. Less is more is the most important thing to remember with shellac. I use wool from felt pac boot inserts for the pad in the muneca and old, well laundered, high quality table cloth linen for the cover -- cheap on E-Bay. Old rag wool socks work also. It seems to me that getting the hang of how much shellac to use with your particular combination of muneca material and your pressure and movement is the key.
Author:  KenH [ Mon Mar 26, 2007 1:01 pm ]
Post subject: 



I have heard of people using 5 minute epoxy instead of using the pumice. What I have not been able to figure out is when to do the epoxy? 


Would you do it right after the spit coats or do you use the epoxy first before anything else is placed on the guitar?  What about sanding this off afterwards? What grit sandpaper would you reccomend?
Author:  SimonF [ Mon Mar 26, 2007 1:18 pm ]
Post subject: 
ALWAYS, epoxy under shellac. NEVER epoxy over shellac. I haven't
personally verified this but I have heard repeatedly that epoxy will not
adhere to shellac.

Also, you want to use a finishing resin epoxy not just a regular 5 minute
epoxy. I use System 3's finishing resin that I get from LMI. Z-poxy is
also very popular. Don't use a regular off-the shelf epoxy.

For instructions, just search the forum archives for "epoxy pore filler".
FYI, I do 3 epoxy coatings and sand back to the wood surface each time.
I then dilute the epoxy in denatured alcohol and rub it on the guitar to
give an even color. It does the job very, very well and can help you
achieve a mirror perfect finish.

Peace Out,
Simon
Author:  KenH [ Mon Mar 26, 2007 2:56 pm ]
Post subject: 



GREAT info !


 


Thanks for the input!
Author:  WaddyThomson [ Mon Mar 26, 2007 3:54 pm ]
Post subject: 

[QUOTE=Bill Bergman]Dr. Scholl's in the pharmacy. It is used to pad sores on feet.

151 proof is 24.5% water, which is too much for French polish. "Pure" grain alcohol at the liqour store (if they carry it) is actually 95% alcohol (190 proof) and 5% water. This is the percentage that ethanol and water evaporate at once they are mixed together. An ordianary still cannot get rid of the last 5%, hence the long standing custom of calling 190 proof "pure" grain alcohol. There are, of course, industrial ways to get the last 5% water out, but then you have something that might be too dry for optimum use. An earlier thread pointed out that denatured alcohol has various and not consistent denaturaing agents, some of which might be deliterious to the French polish.[/QUOTE]


Hi boys & girls, I guess I'm the new guy on the block.  just starting out my building experiences.  Still getting things set up, and working on some of the irritating things like splitting out brace stock.  I have great kindling.  Anyway, I was informed that pure alcohol is a solid.  The 5% water is there to maintain a liquid form.  You can only remove the last 5% with a dessicant, and then you get a powder that apparently is very intoxicating if added to any liquid.  The guy at the liquor store turned me on to a product called Diesel.  It is a pure grain alcohol, 190 proof, and is made in KY.  It is about half the price of Everclear.


Waddy
Author:  Bill Bergman [ Mon Mar 26, 2007 11:23 pm ]
Post subject: 
Pure ethanol is not a powder, it is a liquid. However, it is "dry" of water, so somebody over the years may have thought that it was a dry solid.

I do not know why they call the 190 proof "Diesel" (sounds like truck fuel, which it is not), but if it is bottled for sale in a liqour store it should be safe. It doesn't need to be made in Kentucky, but that is the traditioanl home of hard liquor manufacturer, which is also the traditioanl source of 190 proof alcohol.

The dessicant is used to remove water, but once you have 100% ethanol, you can use that to prime an idustrial operation called extractive distillation, which can remove the last bit of water with a special system of stills. Then you do not need to keep using dessicant.
Author:  WaddyThomson [ Tue Mar 27, 2007 1:05 am ]
Post subject: 

Thanks for the correction.  I have been reading the forum for the last few weeks, and knew, if wrong, it would not stand.  I should have looked it up first.  The person who told me said he had been a chem teacher for 30 years.  I figured he'd know. WRONG!  Seems I never learned it myself in either HS or College Chemistry.  Or maybe my wife told me and, I forgot.


After looking it up, it seems that most of the cost is in the Taxes ($27.00) per gallon.  Diesel is just a brand name.  It was about $12.00 per quart vs over $20.00 for Everclear.  Has anyone ever tried anhydrous alcohol (200 proof)?  It is apparently available out there from industrial suppliers.
Author:  letseatpaste [ Tue Mar 27, 2007 1:14 am ]
Post subject: 
200 proof becomes 190 proof after you open the bottle a few times as I understand. It readily absorbs the 5% water from humidity in the air.
Author:  JJ Donohue [ Tue Mar 27, 2007 1:15 am ]
Post subject: 
200 proof (AKA Reagent Grade ETOH) will cost a lot more than Everclear. Once you open the bottle for a short time it will become 190 proof! It is very hygroscopic and seems to stabilize at 190 proof. Save your money.

Thanks for the tip on Diesel.

Page 1 of 2 All times are UTC - 5 hours
Powered by phpBB® Forum Software © phpBB Group
http://www.phpbb.com/