Tony Joslin on tue 10 jul 12
I had a similar problem a few years back.
At first this sounds like the slip is over flocculated which can be
remedied with Vinegar. But, if you are are sure about the mix then maybe tr=
y
what I did.
I banned all trimmings and scraps from the slip mix. The pour-back from the
moulds was rationed to a maximum of 10% per mix.
This sounds a little wasteful and drastic but weigh this up with the time
and frustration you are experiencing.
Subsequently, I have had no problems fingers crossed.
I hope this helps.
Tony Joslin
-----Original Message-----
From: Clayart [mailto:Clayart@LSV.CERAMICS.ORG] On Behalf Of JRodgers
Sent: 10 July 2012 03:53
To: Clayart@LSV.CERAMICS.ORG
Subject: Slipcasting Clay Problem
I've been slip casting a long time, but I have tun up on a problem that has
me baffled.
My slipcasting clay is Laguna C-5 B-mix. Comes dry in 50 lb bags. Have been
using it for years. I have a tank of slip that has been cast, excess and
scraps recovered and remixed several times, adjusted and the numbers are
right on - density of 1.75, viscosity rate 24 seconds with my viscosity cup
which is dead on. Then, after making a production run, and doing the
recovery thing, on the next round - my clay is flat.
Properly adjusted, but it will not set up in a normal time frame, and in th=
e
normal time frames for each mold, the clay walls are very thin. What
normally would be a 1/4 inch wall thickness in one hour - is far less in
three hours. Then, after emptying the molds, and allowing for setting up of
the new shell - upon opening the molds - the clay is stuck to the molds and
the piece is torn apart - on every single mold. I am stumped.
The only variable I can think of is that I used sodium silicate from a new
bottle, instead of the from the old bottle. The source of the new is
different than the old, but the viscosity appears the same, and they are
both clear.
If anyone has any insight into this problem, I would appreciate hearing
about it. I've got a gallery showing in three weeks and I have got to get
this problem licked.
Thanks,
John
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