These are part of the procedure for the SHAB test. The length of the bars is entered into a recipe record in your account at insight-live.com. When Insight-live has these numbers it can calculate the drying and fired shrinkages.
A method of forming ceramics where a deflocculated (low water content) slurry is poured into absorbent plaster molds, forming a layer against mold walls, then poured out.
During drying, clay particles draw together and shrinkage occurs. During firing the matrix densifies and shrinkage continues. More vitreous bodies shrink more.
In ceramics, glazes and bodies have a chemistry, a mineralogy and a physical presence. All of these need to be understood to adjust and fix issues.