Mould Cleaning

There are a variety of moulds available to kilnformers – slumping/draping, texture and casting are currently popular ones.  Each has a slightly different maintenance regime.

Slumping and Draping

Slumping and Draping moulds are the easiest to maintain, as they are not taken to high temperatures. Normally one application of kiln wash will last very many firings.  The kiln wash needs to be renewed when bare spots appear on the mould.  Some people immerse their moulds in water to wash off the old kiln wash.  This is excessive and requires a long slow drying time for ceramic before you can re-apply the separator.  I’m not even sure the practice is good for ceramic moulds.

Normally, you only need light abrasion such as with a green washing up scrubby to clean off the old kiln wash. You can also use a small nylon brush to take off the old kiln wash and prepare it for a new application.

If you are using boron nitride on your slumping or draping mould, you need to brush off the old separator each time you fire the mould. And then renew the boron nitride surface to ensure there is no sticking.

Texture Moulds

Texture moulds require cleaning before applying any additional separator to avoid blurring or obscuring the textures of the mould.  It is best to use a kiln wash that does not have a lot of china clay in it, such as Primo, to allow easy brushing of the separator off.  If you use a kiln wash with little or no china clay, you will need to clean and re-apply each time you prepare to fire the mould.  Boron nitride works well for texture moulds, but also needs to be carefully brushed off the mould before re-applying the separator in preparation for the next firing.  This is both to avoid blurring the texture and to ensure there is sufficient separator to avoid sticking.

Casting

Casting moulds that are intended to be re-used multiple times are best coated with boron nitride.  The boron nitride should be lightly brushed off after each use to ensure the detail is retained, and then re-coated.  A nylon brush is good for this.

The materials and purposes of moulds have an effect on the separators used and the methods of maintaining them clean.