Potter's Pens are underglaze, in an easy to use pen form. Apply on bisqueware, as you would with pen on paper. Fire to cone 06 - 9, for these colors. AP Non-toxic. Potter's Pen Black potpenblackRegular price: $15.50Sale price: $13.95 Potter's Pen White potpenwhiteRegular price: $15.50Sale price: $13.95 Potter's Pen Orange potpenorangeRegular price: $15.50Sale price: $13.95 Potter's Pen Bright Red potpenbrtredRegular price: $15.50Sale price: $13.95 Potter's Pen Turquoise potpenturquoiseRegular price: $15.50Sale price: $13.95