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Button Lac- Step forward by stepping back
http://w-ww.luthiersforum.com/forum/viewtopic.php?f=10102&t=13763		 Page 1 of 1
Author:  TRein [ Mon Sep 24, 2007 10:00 am ]
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Recently I completed some guitars using Kusmi button lac from Homestead Finishing Supplies. I have let a number of players play them, from inside an air-conditioned room to outside on a shady deck in the summer. There was some perspiration involved in the outside session. The French polished button lac has held up admirably with no imprinting or dulling.
In working with the button lac, it did seem harder than the blonde flakes I had been using (please no Blonde jokes!). When I was doing the final abrasive polish with Novus #2, the shine came up quickly and it has remained bright.
Prior to mid-20th Century, all shellac was handmade, as far as I know. Handmade shellac is processed by melting the seedlac in a cotton bag next to a charcoal fire and wringing the bag to squeeze out the molten shellac resin. The usual, contemporary way of processing seedlac these days is by solvent extraction. There is a picture of handmade shellac and button lac manufacture here.
As you can see in the upper photo, the molten shellac is stretched by hand into thin sheets which are then borken up into the flakes we are familiar with. The second photo shows button lac being poured on a metal sheet for hardening.
I have always been impressed with the finishes on old American guitars like early Martins and Washburns, etc. Most of these guitars I have seen have been played a good bit and the original finish still looks good. Even better than a cellulose finish from the 1940's with the same amount of playing. From what I can gather, early Martins (pre-nitro) were finished with orange shellac and the Lyon & Healy guitars from the same era apprear to be shellac as well. The shellac used to finish these early guitars would have been heat processed, which was the usual way to process shellac prior to cheap solvents becoming available.
So far my results with button lac have indicated that heat processing is an important consideration in determining the durabilty of a French polished guitar. I have used button lac as it is the only shellac I know of that is definitely heat processed. There may be some handmade shellacs available that are heat processed, but none of the standard suppliers I know of carry handmade shellacs. Getting the wax out of button lac can be problematic. I have solved this by placing the broken up buttons inside a coffee filter, tying with string and dropping the "teabag" into a jar with the right amount of alcohol. It takes about 3-4 weeks to fully dissolve the lac inside the filter. After this amount of time, I remove the filter and put it in another jar. More shellac will continue to drain out of the filter. Do not squeeze the filter in an effort to get more shellac out. You will just squeeze more wax out of the bag. After the bag as shed all its liquid in the second jar, you can add the liquid to the first jar and in a week or so, the wax that managed to get through the filter will settle to the bottom of the jar. Interestingly, the level of the wax in the bottom of the jar drops with dewaxed shellac being drawn off the top. I use an eye dropper for that process, being careful not to agitate the jar.
I am putting this info on the Forum in hopes that others who are dedicated French polishers will test my theory about heat processed shellac and post their results here as well.

Tom
Author:  Shawn [ Mon Sep 24, 2007 4:02 pm ]
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Tom, it makes sense. For french polish I use a recipe that Geza Burghardt shared that has different gum resins added to shellac and alcohol and each of he resins has a different softening point and melting point, with or without solvents such as alcohol or water.

In general I think that the addition of alcohol is more to keep the melted shellac in solution than to melt it although in the case of wax it is melted by the alcohol.

I have used kusmi buttonlac in the past and liked it but only moved away from it because of the color of most buttonlac is quite dark. From the description on the site above, it is very encouraging to see that they have lighter colors of buttonlac.

When you consider the harsh chemicals and acids used to bleach and dewax the raw lac into its much less colorful derivatives, it is pretty much a certainty that the chemical transformation of the lac takes away alot of possibly desirable qualities.

Because handmade shellac is processed as little as possible, I think that you are on the right track as far as it being superior to the over processed shellac we use today for french polish.
Author:  burbank [ Mon Sep 24, 2007 4:04 pm ]
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Tom,

Thanks for the info.

I also think my blonde shellac is on the soft side. I changed to amber, from Sunnyside DNA to Everclear, and from no oil to walnut that I'd tested for drying. The finish seems noticeably harder, though I've only looked at two samples. I definitely got a higher gloss with only glazing, no abrasives. Let's say the results are promising.

May have to try some Kusmi button lac. I'll post results, though it will be awhile.
Author:  TonyFrancis [ Mon Sep 24, 2007 6:11 pm ]
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I think that its these kind of details that most makers overlook when making "reproductions" of golden era instruments in their many forms.


Thanks for sharing!


 
Author:  TRein [ Mon Sep 24, 2007 11:53 pm ]
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[QUOTE=Shawn]
..I have used kusmi buttonlac in the past and liked it but only moved away from it because of the color of most buttonlac is quite dark... [/QUOTE]

Shawn,
I have used what was called "button lac" in the past and it was indeed very dark and, oddly enough, in flake form. The button lac I am using now is in silver dollar sized buttons with the maker's mark and the grade stamped in them. I find it doubtful that the button lac flakes are the traditional, heat-processed button lac. The color of the Kusmi button lac from Homestead is a very beautiful golden caramel color.
Author:  Michael Dale Payne [ Tue Sep 25, 2007 2:30 am ]
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I have no qualms with anything posted here. But in real life and some 20 guitars and untold numbers of jewelry boxes and small furnishings I have French polished using either dissolved Blond, Amber or Garnet dewaxed flakes or even Zinnzer's Bull's Eye Seal Coat I have never had a problem with sweat dulling the sheen, imprints or other such maladies.

I am always open to the knowledge other give like adding other resins to the shellac base or to make more of a varnish type base. I have no doubt that many of these are by some percent harder films.

However I have to say on behalf of us that use a Shellac and solvent only formula. When care is given to your boding sessions to properly amalgamate each session and followed with good spiriting off technique, it will makes a big difference in the hardness and durability of a shellac finish.

I am not saying anyone in this post is or has, but over the past couple years it has seemed to me that there has been many incorrect rumors about modern shellac FP films not being durable. When done with care a pure shellac FP finish is not substantially susceptible to sweat or moisture with just basic care. (barring really unusual ph or alcohol levels in the players sweat).
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