Hello, Following up on a thread from August. I did find a good US source of usable collodion (details in a second message) and we have been working on this piano for the past 2 days under the guidance of an experienced collodion voicer (who has chosen not to participate this thread - which leads me to believe that he might want to remain anonymous on this list with regard to this matter). The results are very encouraging. First about the stuff. It's collodion USP diluted with amyl acetate. It's available in various dilutions - I chose to order the thinnest (1%) solution. Amyl acetate for further dilution is also available. The collodion is marked flammable, and it is volatile - but not so much so that they couldn't ship it by overnight air (long story...) We first tested the stuff on an extra hammer from the same set - to see how fast it soaks into the felt. Our mentor felt it was too slow (the amyl acetate flashes off rather quickly - so it needs to carry the solids deep enough into the felt before it reaches semi-solid state and can no longer propagate). We decided that 1% wsa too thick - and cut it 1:1 with amyl acetate - in effect creating 1/2% solution. We determined that the hammers from C#3 and down needed "help" as well as the top 4 treble hammers. The solution is applied to both sides of the hammer, by drops being dripped half way between the strike point and the tip of the molding - and it spreads from there. We turned the action on its end, juiced one side of the hammers, then flipped it over and juiced the other side. We started with 2 drops on each side in the tenor, 4 drops in the bichord and trichord sections of the bass and 6 drops in the sigle strings (where the tone is weakest). In notes 85-88 we did 3 drops on each side. The results were quite noticeable - but not enough (except for note 85 which came up perfect) , and there was little effect on the top 3 notes. So we did a second round of adding various amounts of solution in various sections - except that in the top 3 treble notes we put the stuff directly on the strike point. This brought the tenor and top treble more or less where they needed to be and made a major improvement in the bass. After this our mentor and the other technician left, and I continued very slowly and carefully bringing up the bass by adding solution a few drops at a time to those hammers and to others throughout the piano that seemed to be a bit weaker than their neighbors (about a dozen all together). I could do this, because the stuff feels dry to the touch after 10 minutes - and is fully set after about 1/2 hour. Since I had to work in the concert hall between classes, I could check the tone 1/2 hour after juicing and then again after the class was over (and again this morning) - no change from what it was after 1/2 hour. At this point I am really happy with the tenor, satisfied with (though not ecstatic about) the bass bichords and trichords, and still not really happy with the 8 bottom (single string) notes, though they are much improved. I'll wait to hear what the other tech here thinks before going any further (she'll be here Thursday). Some observations: 1. I started with 30 ml. of 1% solution, and after about 5 rounds of juicing I still have about 25 ml. left. It really takes a tiny amount to make a significant difference. The stuff is volatile, so it's best not to get any more than necessary - who knows what the shelf life is, and how the dilution might change once the packaging is open. But then you can always get the right dilution empirically - by trying it out on a spare hammer of similar density and diluting based on the propagation rate. 2. You don't need to guess at how much solution you need to put in to the hammer on the first pass - the stuff does not "seal" the felt like lacquer or glue it together like plastics (keytop solution) so you can always add more. You can work gradually, a few drops at a time, and stop when the desired result is reached. 3. If by some chance you should end up with too much solution in the hammer(s) - no sweat. Just put a few drops of solvent (amyl acetate) where you dripped the collodion, and it will dilute the stuff that's in the hammer and spread it around over a greater area of the felt - bringing down the tone. 4. When dripped into the hammer's interior, it increases the power with minimal effect on tone color. If you do want to brighten the tone, you can either make sure that it wicks up from the interior of the hammer to the strike point, or (if a big change is needed) drip directly on the strike point. 5. The diluting agent (amyl acetate) flashes off very quickly (dry to the touch in a few minutes, pretty well set in 1/2 hr.) so you can hear results very soon after juicing. You can get quite a bit of voicing done in a short time. Well, that's about it. So far I'll call this mostly successful - with a few problems remaining in the deep bass. It's possible that a better set of bass strings in the singles section might be the cure there... Collodion source details in a second message. Israel Stein -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/caut.php/attachments/20101005/99eec9b9/attachment.htm>
This PTG archive page provided courtesy of Moy Piano Service, LLC