You clean the base of your pot so that it won’t stick to the kiln shelf during firing. Think about it… the glaze melts and forms a glass-like coating when it cools. If it is not cleaned where your pot will sit on the shelf, your pot will be stuck to the kiln shelf… really stuck.
This is important… if you don’t clean your pot properly you might lose your pot (or end up with a pot with sharp bits of glaze on the base). Worse than this, it will also damage the kiln shelf. The shelf will need to be ground using an angle grinder – not a pleasant task. Eventually, after multiple glaze melts the kiln shelf has to be replaced.
To clean the base of your pot, use the sponge tray provided… make sure the sponge is wet and wipe the bottom of your pot on the sponge. Then take a small sponge and wipe over the base of your pot until there is no glaze left at all. You need to wipe a little up the side of your pot – about 5 mm from the base*. This is because some glaze runs.
*note: you might need to make your glaze line higher if you are using a very runny glaze, the application is thick, or you have used multiple glazes (glaze on glaze).