Dave Finkelnburg on sat 17 jan 04
Vince,
I was trying to write what you wrote...sorta...only you wrote it
righter...if you know what I mean... :-)
Had about 30 home schoolers in the studio yesterday...too many, I
know...had to move half the tools out just to fit them in...gave them
all-too brief clay prep, throwing, hand-building demos. Explained your
system of making slurry (yes, I used the word slurry) by drying some of the
clay body to bone dry, then mixing it into a small amount of water to make a
very thick slurry, well stirred so it is without lumps, then scoring both
sides of a joint, coating them with the slurry, and pressing the pieces
together firmly enough to squeeze out as much of the slurry as possible and
guarantee no air is left in the joint. Still didn't do a good enough job of
emphasizing the broad, shallow scoring grooves that are needed, so the
slurry penetrates to the bottom of the grooves...you are so right...air
trapped there is almost a guarantee of joint failure.
Thanks for your help explaining this better. One of the serious
challenges of Clayart is saying every single word exactly right so readers
will understand what is really meant.
Dave, on a frosty, in the teens F, inversion-smog foggy morning in
Idaho, USA
----- Original Message -----
From: "Vince Pitelka"
Sent: Friday, January 16, 2004 7:11 PM
> Dave -
> I regret the necessity of contradicting your generally wise counsel. Slip
> implies a liquid medium. You are right in saying "as thick as possible,"
> but that is a slurry, not a slip. Successful joining benefits from a
thick
> slurry. One should score thoroughly, with a tool that leaves shallow
> grooves (like the Kemper serrated rib) and then apply LOTS of slurry.
> Pressing the joint together extrudes all the excess slurry, which is
easily
> cleaned up. Advising "as little slip as possible" is unwise, since it can
> allow a plane of bubbles to remain in the joint. The whole idea is to
score
> with shallow, wide groves (again, the Kemper serrated rib - never with a
pin
> tool or a wire brush tool that leave deep groves impenetrable to slurry),
> and apply plenty of slurry, so that the joining pressure eliminates all
> bubbles in the joint.
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