Sunday, March 15, 2009

FRENCH POLISHING II - SEALING


REFERENCES AND SOME THOUGHTS ON FRENCH POLISHING IN GENERAL
I always find myself procrastinating a bit when I enter unknown territory - should I do this or should I do that? I found this to be particularly true when it came to applying the finish to this, my first guitar. I set out to do some research to prepare myself and as per usual I found a mammoth of conflicting advice, instructions and guidance. Everything from what type of cloth to make your muneca from, how to grain fill and with what to types of oil to used as lubricant, etc. etc. etc. seemed to have endless possible variables and arguments as to what and what not to use and do.

I also found a most of the advice and tutorials to be incomplete or at least leaving a novice like myself with a lot of unanswered questions, wondering why the author recommended doing things a certain way, and most importantly what to be careful not to do and how to rectify it if you did. It also annoyed me a great deal that almost all tutorials only showed pictures of the back being polished, conveniently skipping how to deal with all the tricky areas such as the bridge, the headslots.

That being said I also found some good references and writings on the matter. Many people recommended the Milburn Tutorial to be the most complete practical guide for the beginner and after having read it, I decided to use that as my starting point and main reference too. Actually I just recently discovered that there are now two different tutorials on Milburn's site. I think I may have used the other one for no particular reason other than that was the one I stumbled upon by default.

Some other resources I found to be very helpful companions to Milburn's tutorial was:
1) The Chapter on French polishing in Ervin Somogyi's book: "Making the Responsive Guitar", which is basically a transcript of the notes he wrote while taking lessons from Eugene Clark.
2) Cindy Burton's article "French Polishing with Eugene Clark" printed in GAL #54 (Red Book V).
3) "An introduction to French Polishing" By Cindy Burton, Greg Beyers, Robert Steinegger and Buzz Vineyard From GAL #14 (Red Book II)

Other references I used that should be mentioned here are among others Courtnall's book: "Making Master Guitars", Bogdanovich' book: "Classical Guitar Making" and LMI's article on "French Polish".

MATERIALS
The first thing I had to do was to choose the materials to make up the finish and something to apply it with. I quickly found there is a bewildering variety of shellac to choose from, each type of shape, refinement and origin providing some sort of unique quality. But instead of even making a slight attempt to figure out what it all meant, I decided just to take the easy way out and go with what Milburn recommended: Dewaxed flakes in a color of your choice.

Ervin Somogyi recommends buying shellac in large quantities to have a supply of consistent quality to work with as he claims that the properties of the same type of shellac can vary a great deal from supplier to supplier, sometime even from shipment to shipment from the same supplier. Though I'm sure this is sound advice, I felt it would be a bit of an overkill for me to start out with and so I opted to get a 8oz jar of 'blonde' flakes at my local Rockler store. I went for 'blonde' color as it was the palest they had and I wanted to get a fairly clear, non colored finish.

Secondly, I had to make a choice of what solvent to use. I read great many debates about whether to use denaturated alcohol or pure grain alcohol. Advocates of the denaturated variety seems to like it mostly because it is cheap and readily available. In a GAL article I also read that denaturated alcohol should be of more consistent quality as it is made under much stricter guide lines.

People who toot grain alcohol as the solvent of choice seems to be swayed mostly because of it's benign quality. This argument appealed greatly to me, but I soon found that it wasn't so easy to get hold of. Aparently it is illegal to sell the good stuff, 190 proof Everclear, in many states including California. Only the 151 proof is available here. However, I manage to find a store in New Jersey who were willing to ship 4 bottle to me. When I asked them if I could get in trouble for it they just said: "Ah, forget about it".

For application I went with Milburn's recommendation and cut up some old white t-shirts and underpants in 4x4" squares. I was quite surprise how many 4x4's I could get out of a pair of old undies. Maybe it's because I still wear army sized boxer brief. Anyone who has done their national service in the Danish army will know that their underpants only come in two sizes, too big and much too big. Moving on.....

PREPARATION
It was time to dissolve the shellac. Milburn suggest to make a 2lb cut for sealing and bodying and so I did. The 8oz plastic container from Rockler had conveniently divided the flakes up in four bags of 2oz each. I put the content of one bag in a glass jar and added 8oz of grain alcohol. I didn't grind or crush the flakes before adding the alcohol as some suggest to speed up the dissolving of the flakes but just left them as they were. It took roughly 24 hours for them to dissolve completely and that even despite the fact that the flakes had caked together into one lump.

Once dissolved I poured half the mixture into a 8oz squeeze bottle also bought from Rockler, covered my bench with a large piece of felt and I was ready to go.

APPLICATION
As per Milburn's suggestion I started off by sealing the purflings on the back in order to prevent the color from the rosewood back, bubinga in my case, bleeding onto the paler wood.

I folded a piece of 4x4" cotton in half and then once more into quarters. The corner of the first quarter was then loaded with about 12 drops of shellac which was wiped on the first purfling and binding following the contour of the guitar in one steady swoop without stopping at any time. Even though I don't think the bubinga really bled very much, it still showed some contamination. Whether this was from resins and oils in the wood or just dust, I don't know, but the cloth was not clean anymore.

To keep things clean the cloth was refolded to a fresh, uncontaminated section, reloaded with about 6 drops of shellac and the second back purfling was sealed, also in one steady swoop. Refolding to the third clean quarter, the cloth was reloaded with a few drops of shellac and the center strip was sealed the same way.

The last clean quarter was recharged and used to seal each section of the back with a coat of shellac, however this time the shellac was applied using a circular motion. After the whole back had been sealed the cloth was disposed of.

It is important to note that I didn't use oil for this. In the tutorial I followed, it stated: "use no oil or alcohol" and so I didn't. Apparently, the other Milburn tutorial advices: "then apply a drop of oil". This is not, in any way, meant as a criticism of the Milburns as I found their tutorial exceedingly helpful, but it is a prime example of how easy it is for the novice to get confused.

The sides were sealed in a similar fashion. A fresh cloth was loaded and first the purfling and bindings were done in one single sweep, then the joint between side and the neck, refolding the cloth to a fresh quarter and reloading it after each sweep. I winged it a bit when I got to the inlay at the butt, by using that quarter for the side as well.

I used two cloths for the soundboard as I quickly ran out of fresh quarters, having to deal with both purling/bindings, the rosette the bridge and the fingerboard as well as the soundboard itself. But in essence it was done like the back and sides, in one continuous sweep where dark and pale woods were joining and finished off with circular motion on the spruce itself. The same technique was used on neck/fingerboard joint and around the headplate veneers.

As the application of the shellac is done with some pressure it was sometimes hard to keep the guitar steady. This was particularly true when I did the back, as in this case the guitar was resting on the bridge and neck only. Doing the areas close to the sides did get a little hard to control. I've only just become aware that Milburn suggest using a neck rest while polishing. For some reason I must have skipped that part of the tutorial, hence my troubles. I believe Eugene Clark clamps his guitars by the neck while polishing.

For those of you who wonder if a person from Blue Man Group came to help out during this, I can attest that it was in fact me wearing a protective nitrile glove from Lee Valley. I think it was probably spurred on by the photographs of Bogdanovich from his book, applying shellac sporting a similar outfit. But while they did prevent the shellac from getting onto my hand I don't think they were necessary, apart from the fact that I didn't have to wipe dried shellac off your hands afterward and then even so.

Being a one man band, it was particularly hard to photograph this process. As the shellac dries almost instantly I kinda' had only one shot at each process, hence the somewhat odd placement of items in the shots here and there. It was all a bit nerve wrecking.

SECOND PREPARATION
After the first application the guitar was inspected again only to find there was several areas that needed some further attention before I proceeded.

First of all I noticed a few areas where the bindings hadn't been scraped flush with the sides. Actually you can see one of these in my previous post, French Polish I - Preparation, in the close up photo of the rounded edge. I also noticed some ripples in the surface of the back around the heel cap where I had scraped it flush. I think it must have stemmed from scraping in the same direction making the scraper follow and accentuate the ripples as the work proceeded. I hindsight I think these could have been avoided had I just changed direction scraping diagonally every so often.

I also noted a tiny bit of bleeding from the bridge onto the soundboard, but as it was so only very little I decided to let it slide.

Last I found a few area around the heel where traces of chisel marks were still visible, as were some planemarks on the back. These were all carefully sanded back again using StewMac's Stikit120 grit followed by 220 grit. After this the whole guitar got another two seal coats for a total of three.


MY FRENCH POLISHING MATERIALS

SEALING BACK STRIP

SEAL COATING BACK

SEALING SIDES BINDINGS AND PURFLINGS

SEALING ROSETTE

SEALING EDGE OF BRIDGE

SEAL COATING SOUNDBOARD

SEALING FINGERBOARD EDGE

SEALING NECK

SEALING HEAD

CONTAMINATED WIPING CLOTHS

BLEEDING FROM BRIDGE

BINDING DETAIL

ROSETTE DETAIL

HEEL DETAIL

THROAT DETAIL

HEAD DETAIL

GUITAR FINISHED WITH THREE SEAL COATS


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