Glen_Deligdisch@sil.org wrote: > > Willard Leverett in his video "Piano Bridge Repair Made Easy" showed > him using a 30 minute epoxy to fill the tinny hairline cracks in both > a treble and bass bridge. The epoxy he was using was very watery and > therefore was good at soaking deeply into the wood. > > Do any of you have suggestions where one would look for the watery > variety? All I have been able to find is epoxy with the consistency > of honey. --------------------------------------------------------------- Glen and List: I realize that several others have already touched on this, but I'll pitch in my two cents worth (no pun intended), for what it's worth. "Free flow of information and knowledge", that's my philosophy! Ok, for split bridges/loose pin problems on any high-quality instrument I immediately recommend a recapping job. It looks neat, it's professional, and its the right thing to do. There are many occassions, however, when we encounter lower quality instruments or customers that are not yet ready to invest in a full rebuilding. In such situations we are often required to "Repair" such bridges. Assuming the bridges are not "beyond all hope" and split deeper than a California fault line, the first and obvious step is to de-string the instrument (or section of bad bridges on less severe cases). Pins must be pulled out carefully. Some remaining tighter pins may take some splinters with them if care is not taken. Except in some more minor sectional repairs, I replace all the pins with new, particularly if I am repining an entire bridge. Pins are cheep, easy, and look more like a professional repair. I recommend the long pins sold by Pianotek (p. A-18). The shorter pins sold by many other suppliers usually bottom out in a old bridge hole making it more difficult to achieve a solid-fitting pin. DO NOT replace loose pins with the next larger size. Unlike tuning pins, each size bridge pin is considerably larger than the previous size. All you will accomplish is split the bridges worth. In terms of epoxies, I highly endorse the "West System" (by Gougeon) 105 Resin with the 206 hardener. This is also available from Pianotek (p. B-19), however here's a hint: It is also available over-the-counter at many marine supply stores for less money. If they don't have it, inquire about price to order it. You can also check out their Web page at: http://www.westsystem.com/ West System 105 has the fantastic advantage of being increadably thin in viscosity. It soaks deep into the wood like a spong filling microscopic cracks and splits you didn't even know were there. At the same time it has just enough body that it still remains manageable. When cured it is absolutely glass-hard, critical for positive transfer of vibrative energy. Many epoxies cure suprisingly soft, particularly the so-called 30 minute varieties. No offense to those who use these types of epoxies- I use them as well, just NOT for bridge work. ***FYI, Gougeon also makes a really great fast-cure epoxy for "other" uses- #865-B epoxy and 865-B hardener. Also available from Pianotek, but check the marinas for this too.*** If there are any larger splits in the bridge, two applications will be neccesary, the first to fill the cracks followed by all needed filing/shaping and sanding, and the second for the pin holes. Epoxying the new pins into the holes will insure a long-lasting reliable repair with no loss of vibration between the pins and the bridges. Likely before this step is taken you will want to LIGHTLY sand down and smooth out the bridge tops. (be careful not to change downbearing). You can also clean out the notches while your at it. At this point the tops will need a new application of "dag", (one of those fun words no-one knows the origin of - or cares). Traditionally dag is made from grafite, but I much prefer gray Teflon (Pianotek P. B-18). Use a small artist brush to apply. A couple of coats may be neccessary. Follow this by burnishing the tops with a thick soft cloth or a piece of hammer felt. The result will be a beautiful shiney finish virtually identical to graphite, but with half the effort and no mess. It looks even better on new bridges. I have seen technicians use a variety of ways to apply the West System 105 to the pin holes. One popular method is to simply dip a piece of heavy music wire into epoxy and dribble it into the hole. A way that works faster and more effecient that I have discovered is using a hypo-oiler bottle. Use the large sized bottle. West System 105 is quite thin when first mixed and can be applied easily in this manor, but you do have to work fast. After about 10-12 minutes it thickens enough that this becomes more difficult. The epoxy MUST be very well mixed or it will not cure evenly- I don't know why, it just does. After mixing for several minutes, quickly pour the mixture into the hypo bottle and go to work. I like to wrap the bottle in a piece of medium felt cloth (to protect the plastic bottle), and then hold and squeeze the bottle with a pair of channel-lock pliers. Quickly move from one hole to the next all the way down the bridge until a adequate amount of epoxy has been ejected into each pin hole. Note that if too much is injected it will squeeze out in a big mess when the pins are inserted. Too little may not do the job- you will have to experiment. Once all the holes have been epoxied you need to immediately empty and clean the hypo-bottle. The pins can wait till afterward, the epoxy will not harden for many hours so you have a little time at this point. Fill and rinse the bottle several times with acetone. If epoxy hardens in the needle, blow it out with compressed air and/or insert a small piece of music wire, followed by a good rinsing with acetone. The bottle can last a long time if it is properly cleaned after each use. The pins can now be inserted into the bridge. I like to tap them in with a piece of brass rod with a small dimple on one end to protect the copper plating. It is likely that some epoxy will ooze out when the pins are inserted. This can be flossed out with a rag and a small dry brush after all the pins are installed, repeating several times with fresh clean rags. If there is any substancial remaining residue, it can be loosened and cleaned with a small artist brush dipped in acetone follwed by a dry rag. This may take some of the "dag" off, however, so some manual touch-up may become necessary. Once the epoxy has cured the tops of the pins can be filed flat for a professional and cosmetically appealing look. A file may be neccessary in tight areas, but I simply take a belt sander with a fine belt and run it across the bridge tops. Obviously this requres a great deal of care- don't go crazy. Keep the machine moving so that the pins don't get too hot. This procedure is actually easier than it sounds. Do a bit of touch-up with a file, clean things up a bit, and your home-free. I first learned this procedure from a very sucessful and proven technician in the mid-west who specializes in bridges and soundboards (I won't mention names here but you can e-me privately). My personal experience with it has yielded great success numerous times, however I will admit that it took several jobs before I perfected my technique. Hopefully it can bring you success as well. Best wishes Rob Goodale, RPT
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