How do you use a clay shrinkage ruler?


  1. Measure the dimension of the finished piece you want using a standard inch ruler.
  2. Find that measurement on the Shrink Ruler on the scale corresponding to the shrinkage of your clay.
  3. Mark or form the wet clay piece to that dimension.

What is shrinkage in clay?

Shrinkage in the drying process occurs due to the loss of water layers. The finer the particle size of the clay, the more water layers; hence the more shrinkage. Clay shrinkage can impact glaze fit and poor glaze fit can cause crazing or glaze shivering problems and reduced strength of your fired wares.

How much does clay shrink during firing?

The firing shrinkage of a clay is usually about the same as the drying shrinkage. Total shrinkage will usually be about 8-12%. The next stage that happens during the firing process is vitrification.

What is a shrink ruler?

Shrink rule or pattern makers scale is a special (oversized) rule used for easiness of pattern making. This oversized scale compensates shrinkage allowance, so one can measure the dimension as ordinary ruler without worrying the contraction of the metal.

What happens if fired clay cools too fast?

Cooling for the Benefit of the Pot Without going too “in-depth”, clay and glaze go through a commercial heating process known as quartz inversion at around 1063 F (573 C). If a pot cools too quickly through quartz inversion, then it can cause the body to crack as it shrinks. This is known as dunting.

Does clay shrink twice?

Shrinking and Weight Loss Clay shrinks both in drying and in firing. Different clay bodies shrink at different rates which can be as little as 4%, or as much as 15% for some clay bodies. We also found through out after years of firing that even with the same clay body, shrinkage can vary 1-2% from batch to batch.

What happens when clay shrinks too quickly?

Atmospheric Drying As the clay is slowly heated, this water evaporates out of the clay. If the clay is heated too quickly, the water will turn to steam right inside the clay body, expanding with an explosive effect on the pot. This will result in the clay compacting and some minimal shrinkage. Continue to 2 of 8 below.

What is the shrinkage rate of stoneware clay?

This can range between a shrinkage rate of 4-15% depending on the properties of the clay and how it is fired. For example, earthenware pots tend to shrink between 6-8% when fired to cone 6. By contrast, stoneware will shrink about 11-13% when fired between cone 6 and cone 9.

What are the three stages when clay shrinks?

Dry. Bisque fired. Glaze fired. Notice the shrinkage at each stage (these were the same size in the dry state).

Where is shrink rule used?

noun A shrinkage-rule; a rule or graduated scale used by pattern-makers, which is a fraction of an inch longer per foot than a standard rule. When used for iron, ⅛ of an inch allows for the shrinkage of the casting in cooling, since every dimension is longer than the nominal or standard one in that proportion.

Is shrink included in patterns?

Pattern shrink, not to be confused with the casting defect shrinkage porosity, is an allowance made on patterns, molds, and cores to compensate for the dimensional changes as a casting cools.

Why does clay get hard when fired?

The strength of fired clay is increased by the formation of new crystalline growth within the clay body, particularly the growth of mullite crystals. Mullite is an aluminum silicate characterized by a long needlelike crystal. These lace the structure together, giving it cohesion and strength.