David, and Israel (thank, Israel for the Spurlock language): We've been using the sizing cauls since they first appeared even though we don't use the Spurlock method of felt replacement. The sizing cauls do a terrific job of creating a stable dimension with which to work. They are inserted when the wood is moist, and there may be minor fiber movement, but I doubt that there is "crushing". When the wood dries, the mortise is consistent and stable. Paul "If you want to know the truth, stop having opinions" (Chinese fortune cookie) In a message dated 04/15/07 14:18:49 Central Daylight Time, custos3 at comcast.net writes: At 11:55 AM 4/15/2007, David Skolnik wrote: Subject: Re: Front Rail Bushings Message: 1 I'm confused or curious about a few of the responses to this question. >From John Delacour come the information about the greater efficacy of cold water in softening hide glue. Can John explain why this would be so? If we are already using Dif and or alcohol as wetting agents, there should be no reason to use hot water, if its only purpose is to overcome surface tension. Also, regarding Bill Spurlock's sizing cauls, which I use, I wonder...I can see how they would work if you want to reduce the mortise size to a uniform width by wetting and glue sizing. The fibres are expanded and then fixed in their new dimension by the glue sizing. However, if the minimum amount of water is applied to wet the cloth and glue, without over-saturating the wood, there would be minimal dimensional change in the wood to begin with, thus making the cauls superfluous? If the wood IS saturated, the expansion would seem to have already taken place by the time the bushings are removed, especially if they are left for a number of hours, as some of the posts suggest. In that case, what is happening to the fibers as the key drys? Do they return to their original dimension or do they remain expanded? If you insert the sizing caul into the wetted mortise after removing the bushing, what happens? Fibre crushing? If the caul is tight when wood is wet, and loose when dry, how much control is there over the amount of shrinkage? Is there a glue sizing effect from residual glue? Wouldn't it be more consistent to allow the wood to expand (stabilize) and then go through with a sized file when dry? If I dug up Spurlock's instructions, I'd probably want to unsend the above. Oh well. David, No need to regret your post. Here is the text about the mortise sizing cauls from Bill Spurlock's website. It covers all the questions raised above by you rather nicely, I think - from Spurlock's perspective, of course... "These special cauls further improve the consistency of your bushing jobs by uniformly sizing the key mortises after removal of the old bushings. Just steam or soak out the bushings, insert a Sizing Caul into each mortise while the wood is still damp, and allow to dry. The mortises will then be very evenly sized with smooth, flat sides as shown below. Bushing stability will also be improved because the moisture-swollen wood will be compacted back to its original dimension, not left in a soft, expanded state." If you want to see the picture, go to http://www.spurlocktools.com/id19.htm Israel Stein -------------- next part -------------- An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/20070415/b3403138/attachment.html
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