If the clay shrinks unevenly, cracks develop. In order to prevent shrinkage and deformation, the firing supports are made from a similar composition of clay, often twice the amount of clay needed for the work itself. Since the supporting structures can only be used once, having shrunk during firing, they represent a considerable production cost.
王俠軍解釋，一旦瓷土收縮得不均衡，就會碎裂，為了預防收縮率差異而變形，一起放進窯爐燒製的托具也特別使用相同配方的瓷土，經常一件作品所需托具的瓷土用量，就是作品本身的二倍，而已經窯燒收縮過的托具也無法再重複使用，成本很高。