Prepare the kiln to heat up before firing up pottery or glass. Pour a sufficient amount of kiln wash into the kiln so that the bottom of it is covered and it has splashed onto the sides. Use a soft cloth to brush the wash in one direction, repeating the process four times across the entire kiln bottom.
Leave the wash in the kiln, secure the lid, and fire it up to between 600 and 675 degrees Fahrenheit; let it cool naturally with the lid on to help it slowly work up to greater temperatures.
If you are firing glass in the kiln, repeat steps 1 and 2, but using glass wash this time. Let the kiln cool down once again with the top secured on.
Place the pottery or glass in the kiln after it has cooled off. Start at the bottom and fill up the kiln working upwards. Make sure none of the pottery or glass is touching, and use a kiln plate or tray if desired.
Set the temperature for the firing process, which depends upon the materials in the kiln. The usual temperature for pottery to be fired is around 1700 degrees Fahrenheit, while the usual temperature for glass to be fired is around 1500 degrees Fahrenheit. For the first firing, pottery is usually in the kiln between 15 and 17 hours, and glass around 11 to 15 hours.