<html> <body> At 09:50 AM 12/31/2007, Mark wrote: <blockquote type=cite class=cite cite=""> As a result, we will continue to use thin CA to treat loose bridge-pins, with strings in place. The application is easy, the results (correcting false beats) have been good, and now we know the glue is making it well below the bridge surface. BTW, I still believe it’s better to saturate one pin at-a-time, than doing a whole section in a series of passes, at a risk of “sealing” the hole on the first pass.</blockquote> Very nice description of the process, with the results checked by sawing and inspecting. As for "sealing" the hole on the first pass, I've tended to think of that as a "feature", not a drawback. Well, I was thinking about loose tuning pins, not loose bridge pins, but in some ways the situation is the same. I've thought about what goes on under the surface when we add CA to the tuning pin where it enters the pinblock, but unlike you I haven't followed up by sawing up an old one after trying the procedure, to see (for a change) exactly where the material ends up. What I have sometimes observed is that when adding small amounts of CA glue to loose tuning pins (grand or upright), most of the time the first application seems to do the trick, but sometimes a second one is required. But I can't remember a time when I needed to add a third dose. I haven't done enough of this or kept records, so this observation is more an inkling than something one could call scientific -- however, suppose I'm right, and there is something special about the second dose, which isn't special about the first or the third? And I thought about what that might be. The prime virtue of water-thin CA for loose pins (bridge or tuning) to my mind is its capacity to follow cracks. It really loves to walk along cracks, the tighter the better.  So, imagine a failing pinblock with delamination and cracks, and one applies CA glue, just a few drops because more runs down the plate, way up where the tuning pin and the pinblock surface touch. And that is a narrow crack, at least some of it is, though where pins have sagged, some is a huge crack. But down where the pin meets the wood, on the sides, it's a small crack - so the CA wicks right down along it. Maybe it couldn't penetrate at the bottom of the hole, where the pin is pressing hard against the pinblock material, but if the pin is loose, somewhere around its circumference we have a tight crack, with just enough contact for the glue to wick, but enough space for it to find passage. However, once that wicking glue meets a delamination, we've got another snug crack, but this one extends for inches and inches. The quantity of CA glue is limited - so that glue wicks right away from the tuning pin. This leaves the large part of the hole as a gap, so that the pin is still loose. BUT - the wicking glue has sealed the cracks as far as it has penetrated. AND, that means that a second application can't wick out of the tuning pin region. It will stay close to the tuning pin, so it can line the hole (like nice cartilage in a joint.) And once it has lined the hole, the pin should be nice and tight, and further applications can't find a way in -- unless the pin is still loose, or works its way loose later. If it's loose, there's a way in for the glue. Only I haven't cut an old pinblock apart to see if this is true. Maybe it's just a theory. So, my hopeful conclusion is that if the cracks are extensive, it's good to put some glue on all the loose pins in the section, so that they can wick in enough to stick the laminations back together. But if the cracks are wide enough and the delaminations long enough that the glue wicks away and doesn't line the holes, a second application after the first one has sealed the exits from the tuning pin's immediate area will leave the CA to act like a gapfiller right next to the tuning pin, and this is a good thing, not something to avoid, since the lack of firmness right at the pin is the problem, so if the material remains right at the pin, it is able to do the most good. Sorry to be so long-winded ... Happy New Year Susan Kline . </body> </html>