Voicing

Voicing

  • 1.  Shellac

    Posted 05-12-2011 16:16
    At 14:33 -0400 12/05/2011, Fred Sturm wrote: >...Shellac is a pretty hard and brittle finish (on wood), but I have >found nitrocellulose lacquer is more prone to "breaking": a blow to >the surface causes the finish to shatter, certainly more so than >shellac. So my guess is that shellac has a bit more bend to it. At >least that is what I have in my mind's eye as a result of sticking >many needles in many lacquered hammers, comparing that to what I >feel with shellac. Fred, I think the reason for this is different, and that is that shellac adheres to the wood (and all sorts of other things) in a very special way; it becomes a part of the wood. Besides that the thickness of a french-polished (shellac) finish is far less than what can normally be achieved with other lacquers. I use shellac exclusively and will no longer touch other lacquers and I apply it by traditional methods. As you say, it is impossible to "shatter" a french-polished finish, but if you were to apply the French polish as a varnish and build up a thick finish and let it go really hard I think you would find it shattered very easily, just as the white hard varnish on a soundboard does. The apparent flexibility of a French-polished finish is due to its extreme thinness and to its complete binding with the wood. This is also what gives the finish that depth that cannot be achieved with other lacquers. In Europe at the beginning of 20th century a lot of black pianos were veneered in black-stained pearwood. Very often, with time, this veneer deteriorates and moves and the French polish cracks. It is impossible to re-finish using French polish because the polish will always crack again. If the wood cracks, so does the finish. My most memorable experience with using shellac for brightening hammers was on a Steinway D belonging to Greg Lake of the pop group Emerson Lake and Palmer. It was a rather gutless piano and he wanted it really bright. Over the space of a few days I applied shellac to the hammers and I added a little green stain to the solution so that I could see just where it was going. The most interesting part of the experience was working through the tone-building together with the customer, who was very fussy and had a very good ear. Today I would certainly fit new hammers and make the best of the piano but in those days good hammers were not so easy to get, and I was not so experienced. JD


  • 2.  RE:Shellac

    Registered Piano Technician
    Posted 05-13-2011 11:07
    John Delacour: "shellac adheres to the wood (and all sorts of other things) in a very 
    special way; it becomes a part of the wood. Besides that the 
    thickness of a french-polished (shellac) finish is far less than what 
    can normally be achieved with other lacquers."

    I have done some French polishing, but when I was comparing shellac with lacquer as a finish, I was thinking of times when I brushed on a couple fairly heavy coats. I have a set of shelves I did that with 30 years ago, and when it gets dinged, the finish dents with the wood, at least considerably more than nitro lacquer (sprayed, about the same thickness) does. With the lacquer, the finish shatters almost without the wood denting. Taking a flake of dried lacquer, similar to one of flaked shellac, it seems more brittle and less "tough."

    In any case, with hammers, we are talking about a very, very thin solution, on the order of 5% or less (at least I am using it that thin). If we think of saturating some volume of fibers, when it dries, the volume of solids will be in that same proportion (more or less - %weight and %volume are not all that different). As I picture it (and I would love to see electron micrographs to clear this up), most of the material would coat the fibers. Some might penetrate the interior of fibers, some would collect in joints where fibers cross. So we end up with fibers with a thin coating, making them stiffer. When we insert a needle, this coating either fractures or bends with the fiber. I am guessing it bends a little more with shellac, fractures a little more with lacquer, though I can't be sure.

    With respect to rates of evaporation and cure, that is an open question, but with such a thin coating, it will not be as long as with furniture finish, where the solvent has to migrate through hardened outer surfaces. Lacquer can be soft on a piano surface for a good long time (I can remember not too many years ago all the new Steinways I saw had big dents where the lid buttons bore on the rim - obviously they didn't allow enough time for curing). Lacquer thinner has more retardants than solvents, as I understand, designed to make subsequent coats melt the undercoat before drying, and to keep from getting blush due to cold from too rapid evaporation. My guess is that lacquer thinner would evaporate about the same as alcohol, maybe a bit slower. Anyone know for sure?

    My take is that the fact a lacquered hammer sounds harder over time has more to do with wear and use than it does with the curing of the material - after an initial week or so. I could be wrong.

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    Fred Sturm
    fssturm@unm.edu
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