Multiple Firings of Kiln Wash

Many people report that they fire multiple times on kiln wash that has not been renewed.  Most add coats over existing kiln wash.  They only remove all the kiln wash when it begins to crack, stick to the glass or gets divots.

We all know that kiln wash fired a second time to full fuse is likely to stick to the glass.  We also know that kiln wash fired to slumping temperatures lasts almost indefinitely.  Somewhere between the two temperatures the kiln wash undergoes a chemical change that makes it more likely to stick to the glass on the next full fuse firing. 

credit: Immerman Glass

Some people continue firing without adding additional layers of kiln wash until cracks, divots, or sticking occurs.  This leads to creating a fix after the failure of the kiln wash. This requires both finding a means of cleaning the kiln wash residue from the glass, and fixing the firing surface.

Others paint a layer of kiln wash on top of the existing separator before high temperature firings. This continues each firing with a fresh layer of kiln wash.  However, the same cracks, divots, and sticking occurs at some point, requiring a complete re-coating of the shelf, and getting the kiln wash off the glass.

credit: Sue McLeod Ceramics

Re-coating of a shelf takes a couple of minutes and can be done with simple tools.  A broad scraper will remove most of the kiln wash.  This can be followed by rubbing with an open weave sanding sheet as used for plaster board or other dry walling.  If you are worried about the dust – which has less risk than fibre papers – you can dampen the surface before beginning the cleaning process.

If the kiln wash has been on the shelf for many firings, it is more difficult to remove, requiring more effort than a single firing.  High temperature firings as for melts also make the kiln wash more difficult to remove. But the same process is used in these cases.

       

Kiln wash in firings at slump and low temperature tack fuses can be reused as many times as it remains smooth and undamaged since the temperature is not high enough to cause the chemical changes.

The ultimate benefit of renewing kiln wash is that not only less effort is required to clean and re-coat, than to fix pieces with kiln wash stuck to them, and also the cost of kiln wash is significantly less than fibre papers.

Removing kiln wash

Applying kiln wash