<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; = charset=iso-8859-1"> <META content="MSHTML 5.50.4522.1800" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY bgColor=#ffffff> <DIV>From West Sytem web page:  <A href="http://www.westsystem.com">http://www.westsystem.com</A></DIV> <DIV> </DIV> <DIV><STRONG><FONT size=4>ADHESIVE FILLERS</FONT></STRONG><FONT = face=Arial size=3><BR><BR><STRONG>403 Microfibers</STRONG><BR>403 Microfibers, a = fine fiber blend, is used as a thickening additive with resin/hardener to create a multi-purpose adhesive, especially for bonding wood. Epoxy thickened = with microfibers has good gap-filling qualities while retaining excellent wetting/penetrating capability. Color: off-white.<BR><STRONG><BR>404 High-Density Filler</STRONG><BR>404 High-Density filler is a thickening = additive developed for maximum physical properties in hardware bonding where = high-cyclic loads are anticipated. It can also be used for filleting and gap filling = where maximum strength is necessary. Color: off-white.<BR><BR><STRONG>405 = Filleting Blend</STRONG><BR>This strong, wood-toned filler is good for use in glue = joints and fillets on naturally finished wood. It mixes easily with epoxy and = lets you create fillets that are smooth and require little sanding. Its color is = a consistent brown, so 405 can be used to modify the shade of other WEST = SYSTEM fillers.<BR><BR><STRONG>406 Colloidal Silica</STRONG><BR>406 Colloidal = Silica is a thickening additive used to control the viscosity of the epoxy and = prevent epoxy runoff in vertical and overhead joints. 406 is a very strong = filler that creates a smooth mixture, ideal for general bonding and filleting. It is = also our most versatile filler. Often used in combination with other fillers, = it can be used to improve the improve strength, abrasion resistance, and = consistency of fairing compounds, resulting in a tougher, smoother surface. Color: = off-white. </FONT></DIV> <DIV><FONT face=Arial size=3></FONT> </DIV> <DIV><FONT face=Arial size=3>Their products are excellent. I have = been using them for more than 20 years in marine applications. They have excellent technical support and are willing to help you with any questions by = email or on the phone. They do not charge for a brief dose of expertise - but I = think they make up for it when selling you the epoxy! Their variety of hardeners = really lets you control things also. I keep three types on hand: Slow cure, = Extra Slow cure, and Coating hardener. Their handy pumps for the hardener and resin = are a MUST!</DIV></FONT> <DIV><FONT face=Arial size=3> </DIV></FONT> <DIV><FONT face=Arial size=3>I often use the #404 High-Density = filler for big cracks. Maybe it is overkill. I do know it mixes a lot easier than the #406. It sounds to me like Del was recommending the #403 and #406. = Maybe next time I will try that. </FONT></DIV> <DIV><FONT face=Arial size=3></FONT> </DIV> <DIV><FONT face=Arial size=3>Roger - I think Del was pointing out = that West System with no filler may be a bit too plastic when one is trying to = actually repair a broken bridge - one that is cracked to the extent that it needs = to be held back together - as opposed the the more common case where we are = filling a small crack next to the bridge pin. I think when you have a large = crack (although I can't imagine a large crack on a not-terribly-old Bozy = across only 5 or 6 notes) you will be able to stuff the non-wicking thickened, = not-so-plastic, epoxy into the crack efficiently. Maybe that should be the deciding = factor - if the crack is big enough to get thickened epoxy into it - do it. If the = crack is so small that you need the wicking action of the unthinned epoxy, then = go that route. I agree, put the pins into the uncured epoxy.</FONT></DIV> <DIV> </DIV> <DIV>Regarding clamping. Del is right on. Epoxy requires a minimum = thickness of product in the joint. For the bridge, if the bridge is cracked so much = that you need to reposition the two halves, yes, of course clamp. But clamp to = position things correctly only. Do not clamp so hard as to squeeze out too much = epoxy. You gotta leave a good coating in the joint. Do not clamp it like you = would clamp a bridge cap to a root with hide glue. Sometimes, if I am jointing = two perfectly mating surfaces together with epoxy, and the situation is such = that it will be hard not to squish the two joining surfaces together tightly, I = will actually drill a bunch of shallow holes, route out a series of shallow = troughs, or whatever to be sure that I have sufficient joining surface area that = has a good 1/16" or whatever layer of epoxy retained in the joint.</DIV> <DIV><FONT face=Arial size=3></FONT> </DIV> <DIV><FONT face=Arial size=3>Regarding solvents. Del is right on = with his description of using a solvent for cleanup, as opposed to using it as an = additive for thinning the epoxy. For cleanup, I use acetone. It works = excellent on non-cured epoxy. It works well even when the epoxy is semi-cured into = a rubbery state. That is what West System recommends as a cleanup solvent. = I don't know how laquer thinner would work - never used it. I do know that I can = tolerate a little acetone vapor better than laquer thinner.</FONT></DIV> <DIV><FONT face=Arial size=3></FONT> </DIV> <DIV><FONT face=Arial size=3>Terry Farrell</FONT> <SPAN id=__#Ath#SignaturePos__></SPAN> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A title=tompiano@gate.net href="mailto:tompiano@gate.net">Tom = Servinsky</A> </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A = title=pianotech@ptg.org href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, September 01, = 2001 8:36 AM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: split bridge</DIV> <DIV><BR></DIV> <DIV><FONT size=2>Del,</FONT></DIV> <DIV><FONT size=2>Might want to mention that West does provide the = thickening material for changing viscosity. #403 Micofibers Adhesive is the name.</FONT></DIV> <DIV><FONT size=2>Tom Servinsky,RPT</FONT></DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A title=pianobuilders@olynet.com href="mailto:pianobuilders@olynet.com">Delwin D Fandrich</A> = </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A = title=pianotech@ptg.org href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, September 01, = 2001 12:49 AM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: split = bridge</DIV> <DIV><BR></DIV> <DIV><FONT color=#000080></FONT> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000080 2px solid; MARGIN-RIGHT: 0px"> <DIV style="FONT: 10pt arial">----- Original Message ----- = </DIV> <DIV style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: = black"><B>From:</B> <A title=davidlovepianos@earthlink.net href="mailto:davidlovepianos@earthlink.net">David Love</A> = </DIV> <DIV style="FONT: 10pt arial"><B>To:</B> <A = title=pianotech@ptg.org href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV> <DIV style="FONT: 10pt arial"><B>Sent:</B> August 31, 2001 7:51 = PM</DIV> <DIV style="FONT: 10pt arial"><B>Subject:</B> Re: split = bridge</DIV> <DIV><BR></DIV> <DIV><FONT size=2>Joe:</FONT></DIV> <DIV><FONT size=2></FONT> </DIV> <DIV><FONT size=2>Why would you not clamp epoxy?  The bridge needs to be pulled back together, among other = reasons, to get the pins back in the right position.  My conversation = this date with Roger Weisensteiner confirmed my belief that this would = be the method of choice for making this repair.  He suggested = using a two part epoxy (e.g. West System type) and clamp it back together reinserting the pins either before or after it dried.  My = concern with after is that if I have to redrill the case might be in = the way.  So I will probably reinsert the pins before it dries.</FONT></DIV></BLOCKQUOTE> <DIV dir=ltr><FONT color=#000080 size=2>Unlike nearly all = other adhesives, epoxy is an excellent gap filler. In fact, it actually requires a = rather thick glue line for best adhesive strength. Rather than say "don't = clamp at all," I would say clamp lightly--just enough to bring the crack just = shy of fully closed. </FONT></DIV> <DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV> <DIV dir=ltr><FONT color=#000080 size=2>West System is a good = epoxy for this repair, but it should be used with some kind of filler to improve = its resistance to cold flowing--it is a plastic, after all. I would = suggest a bit of micro-fiber (ground cotton fibers) to add strength and some = colloidal silica to add hardness. Try equal amounts of each, adding just = enough to bring the matrix up to the consistency of warm peanut = butter.</FONT></DIV> <DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV> <DIV dir=ltr><FONT color=#000080 size=2>You'll want to insert = the pins before the epoxy hardens. And you'll want to clean up the excess and = squeeze-out before it all fully hardens as well. Things can get = pretty difficult after the whole mess gets hard.</FONT></DIV> <DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV> <DIV dir=ltr><FONT size=2></FONT> </DIV> <BLOCKQUOTE dir=ltr style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; = BORDER-LEFT: #000080 2px solid; MARGIN-RIGHT: 0px"> <DIV><FONT size=2>Regarding solvents and epoxy, I have, in the = past, repinned bridges putting a drop or two of epoxy in the bottom of = the bridge pin hole prior to inserting the pin.  The squeeze out = I have cleaned up by brushing it onto the notch using an acid brush with = a bit of lacquer thinner.   I think I may have been introduced to = this technique by Bill Spurlock in a Journal article in fact.  = Though I recognize the controversy surrounding epoxying bridge pins in, I = wasn't aware that a bit of lacquer thinner was compromising the strength = of the epoxy.  </FONT></DIV></BLOCKQUOTE> <DIV dir=ltr><FONT color=#000080 size=2>Joe was referring to = the practice of adding a thinner such as lacquer thinner to the epoxy to thin it out = and get it to flow into the cracks more readily. It is true that you can = thin epoxy in this manner, but it does chemically weaken the material and = introduces a certain amount of shrinkage as the thinner flashes out of the = mixture. It is doubtful that you will get enough thinner into the epoxy mix using = it as you describe.</FONT></DIV> <DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV> <DIV dir=ltr><FONT color=#000080 size=2>Incidentally, epoxy = cures chemically, it does not "dry. It is this property that keeps it from = shrinking as it sets up. There is no--or at least, very = little--solvent to flash out.</FONT></DIV> <DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV> <DIV dir=ltr><FONT color=#000080 size=2>Regards,</FONT></DIV> <DIV dir=ltr><FONT color=#000080 size=2></FONT> </DIV> <DIV dir=ltr><FONT color=#000080 size=2>Del</FONT></DIV> <DIV dir=ltr><FONT color=#000080></FONT> </DIV></BLOCKQUOTE></BLOCKQUOTE></BODY></HTM= L>