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. Even one percentage point can make a difference in the final product depending on your need for precision. Your design, therefore, needs to account for the shrinking for the temperature to which you fire. For example of the clays we use at Lakeside Pottery is Standard's Baldwin 192 and it is specified to shrink 11% for cone 6 firing temperature. Our testing showed that about 5% shrink during the drying process, 1/2% during bisque firing (cone 06) and 5.5% during glaze firing (cone 6). The total of 11% is shown in the lantern picture below (before and after).