Megan Ratchford on fri 9 nov 01
Howdy to all! I'm new here and already I'm thinking up strange =
questions.
Here's a good one:
I work in two different studios simultaneously-- (yes, it's true, I have =
no social life)--and I use the same clay body and the same white slip =
recipe at both studios. Also, since both studios receive their supplies =
from the same retailer, the chemicals are the same (within reason of =
course.) =20
Here's the question: At one studio I throw my pieces and slip at =
leather hard. No problems with the slip, I can get it nice and gloppy =
with thick and thin application, no problem. At the other studio I =
apply the slip in the same way and if it's thicker than a wash the slip =
pops off the pot before and during bisque. Same clay, same slip recipe, =
same me. Is it the water? (The studios are in different towns.) I have =
tried several slip recipes with the exact same results. I'm getting =
quite a headache from all of this, anyone want an aspirin?=20
Thanks!! Megan=20
Snail Scott on sat 10 nov 01
At 07:16 PM 11/9/01 -0700, Megan wrote:
Is it the water?
Could be! And, does either studio have a water-softener?
That will change the mineral content even if the water
supplies are similar. Perhaps the 'good slip' studio
water has minerals (soluble salts of some sort) that are
slightly deflocculating the slip; this would allow it to
be mixed with slightly less water, so it would shrink less
while drying and not crack off.
Try carrying water from the 'good slip' studio, and mixing
up the slip for the 'bad slip' studio with that. (You could
transport the slip itself, but just switching water will
give only the one variable at a time.) Or, get some bottled
water and mix slip in both places using the bottled stuff.
You could even try comparing regular bottled (filtered)
water with distilled water, or other types, if you wanted
to be really investigative!)
If it is a deflocculation effect, you could find out by
mixing both slip batches with exactly measured amounts of
me deflocculating mineral in the water. If so, adding a bit
of deflocculant to the 'bad' slip may help it behave better.
-Snail
Snail Scott on sun 11 nov 01
Oops -
It seems that something ate several lines of my 'bad slip' post;
didn't make much sense, did it? Here's what that last paragraph
was trying to say:
>If it is a deflocculation effect, you could find out by
>mixing both slip batches with exactly measured amounts of
>water to each slip batch. If there is a deflocculating
>mineral in the water, the batch mixed with that water should
>become workable while the other batch is still a bit thicker-
>seeming and needs more water. If deflocculation is at work in
>the 'good' slip, adding a bit of deflocculant to the 'bad'
>slip may help it behave better.
>
> -Snail
Russ Fish on mon 12 nov 01
I have your same issue when producing slips. The resolution is to better
understand the hardness of your water. The water hardness plays a big role
for me on what chemistry I use to obtain the same rheology, casting rate,
and firming texture.
Russ
----- Original Message -----
From: "Snail Scott"
To:
Sent: Sunday, November 11, 2001 4:14 PM
Subject: Re: strange slip sluffing
> Oops -
>
> It seems that something ate several lines of my 'bad slip' post;
> didn't make much sense, did it? Here's what that last paragraph
> was trying to say:
>
> >If it is a deflocculation effect, you could find out by
> >mixing both slip batches with exactly measured amounts of
> >water to each slip batch. If there is a deflocculating
> >mineral in the water, the batch mixed with that water should
> >become workable while the other batch is still a bit thicker-
> >seeming and needs more water. If deflocculation is at work in
> >the 'good' slip, adding a bit of deflocculant to the 'bad'
> >slip may help it behave better.
> >
> > -Snail
>
>
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Megan Ratchford on mon 12 nov 01
Thanks to Bonnie and Russ!!
Russ, do you add any source of sodium to correct the hardness of the =
water? This really could be the source of the problem as all other =
variables have checked out identical.
Megan
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