Mark Burleson on mon 15 jul 96
Greetings,
I have a dry mix clay body, C/6 white stoneware that I would like to make a
casting slip from.
I am having provblems with specific gravity, I am confused about how much
and what kind of defloculant to use, and what the specific gravity should
be. Also, I need to know what percentage of soda ash, sodium silicate and
water to add. I have been using Darvan 7 unsuccessfully or improperly.
Please help! Thanks.
--
Interpath - Your Internet Service Provider
Tom Buck on mon 15 jul 96
Our local supplier provides a dry-blended body (usually high-talc for C6 or
lower) that makes a good casting slip. And this is the recipe offered:
100 dry-blended clay
0.22 soda ash
0.67 sodium silicate (waterglass)
44.5 water
and this is the method:
1) weigh water, place in bucket.
2) weigh soda ash, dissolve in the water.
3) weigh the clay mix and add slowly to the water via sprinkling on top.
4) weigh sodium silicate, add slowly to bucket.
5) stir bucket contents vigorously
6) check the slip density (aka specific gravity) and you are aiming for a
density of 1.65 g/mL - 1.70 g/mL. Add water if needed.
7) pass slip through a screen 50 mesh or smaller before use.
The viscosity of the slip, if you can measure same with the appropriate
device, should be between 1 & 5 centipoises (castor oil is 10 cp)
If the dry mix is the same as the local one, this method will
yield a workable casting slip. However, not all clay mixes are created
equal, so be prepared when adding the sodium silicate to recognize when
the slip has "thinned" to a pourable viscosity, and then do NOT add any
more sodium silicate because doing so will only increase the viscosity.
TomB Hamilton ON Canada URL http://digitalfire.com/magic/tombuck.htm
| |
|
