Nancy Udell on mon 21 jul 08
Yippee-eye-oh-kai-yea! Thanks again to all who gave advice and
knowledge. Me thinks i am over the hump. What helped? First, the
notion which i did not understand that specific gravity will not be
affected by the defloculant. And having the confidence to know to
adjust the specific gravity first, and then adjust the viscosity was
VERY helpful.
Also, this seems silly, but since I was confident that my slip was
correctly formulated, I was able to see that things were working much
better than I thought. For some reason, I had the impression that i
was supposed to be able to lift the casting out of the mold about 1/2
hour after i poured out the excess slip. I now understand that it
will separate in that time, but take longer to firm up and even
longer to be bone dry.
It's amazing how one little piece of info can act as the the red
plastic cracker jack strip, revealing the answer underneath.
Obviously still a way beginner here, but feel more confident and able
to stumble thru a bit better.
There still does seem to be some discrepancy about whether to weigh
the liquid sodium sil as a dry material or to measure liqid ounces.
Perhaps the differential is small enough and the acceptable range of
defloculant large enough that it ends up not mattering?
Nancy Udell
Santa Fe, New Mexico
505.984.9907
www.clayandcolor.net
John Rodgers on mon 21 jul 08
Nancy,
Good to hear you have conquered the monster!!! Slip casting can be fun
when it the slip is right.
Interesting to hear about the sodium silicate. In al the years I have
been slip casting, I have never weighed Sodium Silicate. I simply pour
up a cup full, the cut it with water so it is a 50-50 mix, then I
dribble a little into the slip as it mixes, then test viscosity, if it's
not right, I repeat the process until I have the best flow rate from
the viscosity cup.I guess I have been doing this long enough for it to
have become second nature. I can tell pretty much what is happening just
by watching the slip change as the water/silicate mixture is added. But
I still rely on my instruments for testing. It has been said, and some
practice it - but you can dip a finger in the slip, and if it is
properly adjusted three drops should fall from your finger - and no more
- no less. If it does that, it is right on. I do that - but I still
calculate the density and the viscosity. Anytime you can quantify the
work, you are ahead of the game. So always check our numbers.
Regards,
John Rodgers
Chelsea, AL
Nancy Udell wrote:
> Yippee-eye-oh-kai-yea! Thanks again to all who gave advice and
> knowledge. Me thinks i am over the hump. What helped? First, the
> notion which i did not understand that specific gravity will not be
> affected by the defloculant. And having the confidence to know to
> adjust the specific gravity first, and then adjust the viscosity was
> VERY helpful.
>
> Also, this seems silly, but since I was confident that my slip was
> correctly formulated, I was able to see that things were working much
> better than I thought. For some reason, I had the impression that i
> was supposed to be able to lift the casting out of the mold about 1/2
> hour after i poured out the excess slip. I now understand that it
> will separate in that time, but take longer to firm up and even
> longer to be bone dry.
>
> It's amazing how one little piece of info can act as the the red
> plastic cracker jack strip, revealing the answer underneath.
>
> Obviously still a way beginner here, but feel more confident and able
> to stumble thru a bit better.
>
> There still does seem to be some discrepancy about whether to weigh
> the liquid sodium sil as a dry material or to measure liqid ounces.
> Perhaps the differential is small enough and the acceptable range of
> defloculant large enough that it ends up not mattering?
>
> Nancy Udell
> Santa Fe, New Mexico
> 505.984.9907
> www.clayandcolor.net
>
>
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