<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Re: Hardening Bridge Caps</title></head><body> <div>David, Dale, Dell and all,</div> <div><br></div> <div>I also agree with the practice of coating the top of the bridge. One of the reasons why multi-laminated bridge caps are so effective is that the laminates are permeated with glue during the gluing process. Any minor checks in the laminates, which can occur if they are dried too fast at any time from tree to product, are simply glued up to eliminate the risk of splitting. But the top surface of the top laminate will not be permeated fully with glue unless it is also deliberately coated on the top surface.</div> <div><br></div> <div>After finding that the top laminate can occasionally develop small checks after the bridge is pinned unless the top layer of the top laminated is also coated with glue, we have been manufacturing our laminated bridge caps by applying a layer of glue over the top laminate also. The plastic sheet which is placed underneath and over the top of the entire cap before the vacuum press diaphragm is placed in position prevents glue from getting all over the diaphragm. When the cap comes off the press both the top and bottom surfaces are sanded prior to fitting to a bridge. Caps laminated in this fashion are essentially a matrix of West system and maple.</div> <div><br></div> <div>In your case David, it might be worth considering making your own multi-laminated caps. It would save you the detailed clean up of the pin holes before pinning. We don't make our own laminates these days, since quarter cut 0.5 mm thick Rock Maple veneer can be purchased locally. We use seven layers for each cap to make up 3.5 mm, just enough thickness to accommodate the notching depth. The thinner veneer layers also allow for a more complete permeation of glue, which I prefer.</div> <div><br></div> <div>Below is an image-link showing the treble end of the bridge from our most recent piano, no. 7. The notching extends down into the seventh laminate.</div> <div><font face="Lucida Grande" size="-4" color="#000000">http://members.optuszoo.com.au/ronovers/oversno7.2.jpg</font ></div> <div><br></div> <div>Ron O.</div> <div><br></div> <blockquote type="cite" cite>When cutting a new bridge cap I typically paint on a low viscosity epoxy to<br> both harden and seal the cap.  I do this after drilling and notching but<br> before pinning, sanding back the bridge top flat again before inserting the<br> bridge pins. <br> <br> I'm considering doing this same process with a thin CA glue which seems like<br> it will offer some advantages: cures faster, wicks into the wood better,<br> requires less sanding afterward. <br> <br> Any thoughts on the differences in terms of providing a seal and adding<br> density to the wood between the two substances?<br> <br> David Love<br> davidlovepianos@comcast.net<br> www.davidlovepianos.com</blockquote> <div><br></div> <div><br></div> <x-sigsep><pre>-- </pre></x-sigsep> <div><font face="Times New Roman" size="+1" color="#0000FF"><b>OVERS PIANOS - SYDNEY</b></font></div> <div><font color="#000000"><i>   </i></font><font color="#0000FF"><i>Grand Piano Manufacturers</i></font><font color="#000000"><br> _______________________</font></div> <div><font size="-2" color="#000000"><br> </font><font color="#000000">Web http://overspianos.com.au</font></div> <div><font color="#000000">mailto:ron@overspianos.com.au<br> _______________________</font></div> </body> </html>