text: Shrinkage after solidification can be dealt with by using an oversized pattern designed specifically for the alloy used. s, or s, are used to make the patterns oversized to compensate for this type of shrinkage. These rulers are up to 2.5% oversize, depending on the material being cast.  These rulers are mainly referred to by their percentage change. A pattern made to match an existing part would be made as follows:  First, the existing part would be measured using a standard ruler, then when constructing the pattern, the pattern maker would use a contraction rule, ensuring that the casting would contract to the correct size.
  Note that patternmaker's shrinkage does not take phase change transformations into account. For example, eutectic reactions, martensitic reactions, and graphitization can cause expansions or contractions.