Kiln Wash Mix

There seems to be a view that the exact consistency of the kiln wash mix is important.  Within limits the mix proportions are not vital.  The general recommendations from manufacturers is one part powder to five parts water – both by volume.  This is a good guide for general use.

 

It is possible to make the kiln wash mix too thick.  If it goes onto the shelf or mould in a pasty fashion it is too thick.  A thick mixture leaves definite streaks and uneven levels that are difficult to smooth and level.  If you get these effects, scrape it off and put it into a jar with more water.  Mix until it is creamy to avoid lumps.  Then add more water until you have a very liquid mix.  It needs only be a little less runny than plain water.

 

Is it possible to have too thin a mix of kiln wash?  I suppose it is, but not likely.  If you feel it is too thin, you only need to add more coats of the mix until the shelf surface is obscured. Often when the mix seem thin, it is because the powder has separated from the water.  It is necessary to stir the kiln wash thoroughly to get all the solids in suspension.  Then frequent stirring during the application is necessary to keep the mix even at both the top and the bottom of the container.  Storing the mixed kiln wash in a clear container will enable you to see if kiln wash is still settled on the bottom.

 

The object of the kiln wash is to provide a separator between the supporting surface and the glass.  It needs to be only a film of separator to be effective.  In fact, if the kiln wash is too thick, it will flake and stick to the back of the glass.  In the case of kiln wash - more is definitely worse.

 

For very absorbent materials such as vermiculite or fibre board, I mix kiln wash thicker – about 1:3.  The idea behind this is to reduce the amount of water the mould absorbs.  With less water in the mould, less drying time is needed, especially with a vermiculite mould, where steam pressure could break the mould.