The surface of CALM after a sponge has been used
Sponges are very useful in pottery. They carry water to your pot to keep it wet while you throw. They reduce the friction between the clay and your fingers. Most importantly, they remove excess water from the surface of your pot to keep it from getting soggy and later cracking.
Keep in mind that they are not all created equal. Let's take a look at some different types and their uses.
Types
There are many different types, but they all fall under two main categories, natural and synthetic.
Natural varieties have been harvested for use in pottery used for centuries. They are naturally strong and soft and are excellent for use in pottery.
They can be purchased in different shapes, sized and thicknesses, as well as in different softness. Although the natural variety is more expensive, they are generally preferred by most potters.
Synthetic ones are now made out of a variety of materials. With this variety also comes a variety of quality and durability.
Everyday kitchen sponges could actually be used to make pottery. However, they tend to deteriorate quickly and you may find unwanted chunks of sponge in your pot later. I recommend using one designed for throwing pottery.
Several synthetic varieties are available at pottery supply stores that are specifically suited to pottery. These will be stronger, softer, and less prone to tear apart while you are throwing.
They are inexpensive, and well worth the advantages they offer.