Tuesday, April 9, 2013

March 31st Hint of the Week

When to use Magic Water? (from Lakeside Pottery)
Magic water is used when the bond between two pieces of clay is a suspect for cracking during drying or bisque firing. Cracks can occur in the following conditions:
  1. When one piece of clay dries faster than the other which typically occurs when it has a smaller mass or thinner than the other piece (e.g., a mug handle).
  2. When one clay piece is applied to another piece that is already a dryer leather-hard (e.g., when waiting for a thrown pot to harden before applying hand-built piece).
These two conditions are more susceptible to cracking because when one piece is dryer that the other, it is therefore shrunk more than the other and will not continue to shrink uniformly after they are attached to each other, thus - creating stress.
Why does Magic Water work?
Sodium in the soda ash and the sodium silicate is a very powerful flux. The silica in the sodium silicate adds some glass-former. The water is to dissolve the soda ash (which is soluble) and therefore travels a little way into the wet clay. The sodium silicate is sticky and dries really hard and faster than the clay does. The end result is that the Magic Water makes a sticky layer of almost-glaze that soaks into the surrounding clay and dries hard. Thus, cracks are prevented in the drying and the bond is stronger after firing.
How to make Magic Water - Recipe?
  • 1 gallon of water
  • 3 table spoons of liquid sodium silicate
  • 1 1/2 teaspoons of soda ash

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