It does creep. Given enough time, enough stress and/or enough heat--PVAs are thermoplastics--all PVA adhesives will exhibit some creep. At question is whether or not these things will exhibit enough creep in ways that will be of any consequence to us as piano technicians and rebuilders. Years back I used to worry about this stuff but then I actually started to think--I know, unusual, but it does happen--about how we use adhesives in real life and these days I don't waste a whole lot of worry time on them. With very few exceptions glue joints in pianos are not subjected to high sheer-stress loads. The most obvious exception might be the rib-to-soundboard panel joint of a compression-crowned soundboard system. Here, I would argue, age- and compression-related long-term creep--i.e., compression-set--within the soundboard panel itself is going to be a far bigger concern than any relatively minor amount of creep that might be taking place in the glue joint. And in some applications a bit of creep might actually be to our advantage; a large cross-lapped joint, for example. PVA adhesives are not approved for use in structural, load-bearing laminated beams such as those used in some building designs (many churches, for example) or for similar beams used in road bridges and railroad bridges. The concern in building beams is not so much that they will creep over time but what will happen to them in a fire. PVAs soften when exposed to heat and it's not a good thing if structural beams fail while the fire department is trying to put out the fire. Laminated structural beams used in road bridges are subjected to heat from the summer sun, not to mention water from periodic rains. PVAs are not generally recommended for use in bent-laminated structures such as grand piano rims or vertically laminated bridges. Still, CP Adhesives (http://www.cpadhesives.com/) lists CP-0200, a cross-linked PVA adhesive similar to Titebond II, as one of their recommended adhesives for curved laminations. And I have to confess--please don't tell the glue police!--I've used Titebond II to glue up more than one vertically laminated bridge body and, as far as I know, twenty and thirty years later they haven't yet come apart or straightened out. If I start building curved laminated structural beams for a railroad bridge to be installed in Arkansas I'll probably consider using some other type of adhesive. There are other adhesives that would better stand up to those extremely hot and humid summer days. I also don't use PVAs for gluing up grand rims. For one thing, the open-time for most PVAs is not long enough; they start to skin over before the whole book of veneers could be assembled and loaded into the press. But the shear stress on the glue joints in some areas of the bent laminated rim are extremely high. I doubt this would be a problem once the belly structure was fully assembled but until then I'd think spring-back might be a problem. It would be an interesting experiment and I might well be surprised. It wouldn't be the first time. So, to your clavichord; as long as you don't put those parts you've glued up with Titebond outside in the summer sun or the winter rain they should work just fine. Ron's point is well taken, though. It would be nice to have access to a lot more information on the adhesives these companies are trying to sell to us. You have to figure it exists somewhere. There is some information available but you have to search for it. I've attached the product data sheets for Titebond Original, Titebond II and Titebond III. (Does this list still accept attachments?) Chapter 10 of the Wood Handbook is all about adhesives and the bonding of wood. Either specific chapters or the whole book can be downloaded (free) as a PDF file from http://www.fpl.fs.fed.us/products/publications/several_pubs.php?grouping_id= 100&header_id=p I may have some additional information somewhere. If I come up with anything I'll add it to the list. But I don't think I've ever seen a Shore hardness rating for any adhesive.... ddf Delwin D Fandrich Piano Design & Fabrication 6939 Foothill Court SW, Olympia, Washington 98512 USA Phone 360.515.0119 — Cell 360.388.6525 del at fandrichpiano.com — ddfandrich at gmail.com -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of David Doremus Sent: Friday, February 24, 2012 9:18 AM To: pianotech at ptg.org Subject: Re: [pianotech] Bolduc glue There always seems to be some mystique about glue, and no solid answers. I have been assured for years by a few of the 'earlier than thou' instrument makers that Titebond is completely unacceptable for instrument work as it creeps and doesn't dry as strong as hide glue. No one can prove this, as far as I know, and I have a 5 8va clavichord I made, starting almost 20 years ago, the soundboard panel, bridge plys and keyboard panel as well as every joint were glued with Titebond and show no signs of any failure yet. I'd love to see glue data like that before making a decision on what to buy rather than relying on what is accepted wisdom in some circles but not in others. --Dave On 2/23/12 12:19 PM, Ron Nossaman wrote: > On 2/23/2012 11:48 AM, Encore Pianos wrote: >> Ok, so who's the manufacturer? > > How would I know? If we had Shore hardness values available for glues > we can look up, we could very possibly find a number of glues just > like it for probably a third the price. -------------- next part -------------- A non-text attachment was scrubbed... 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