Clumping Kiln Wash

There are some reports of properly prepared kiln wash (1 part powder to 5 parts water by volume) clumping or going onto the shelf or mould unevenly.

My experience is that this happens on shelves that have been kiln washed and fired several times.  The dry kiln wash that has already been fired absorbs the water quickly leaving unevenly applied kiln wash.  The water is absorbed so quickly that it leaves unevenly distributed kiln wash over the existing, already fired kiln wash.

The immediate response of diluting the kiln wash even further leads to a lot of water being absorbed into the shelf leading to longer air-drying times.  It also risks getting insufficient kiln wash over the existing kiln wash. This risks the kiln wash sticking to the fired glass, which is the opposite of the intention of using fresh separator.

When the new kiln wash solution begins to clump, it is time to stop adding more over the top of the old.  It is time to remove the old, clean the shelf and start with a new smooth kiln washed shelf.  It does not take long and gives the satisfaction on knowing the bottom of your pieces will be flat.

Applying new kiln wash repeatedly over old leads to uneven application and clumping of the new.