Underglaze Pen 900-1040°C – Hobbyceram You can use underglaze pens to make detailed drawings, to draw motifs, to make sketches, to sign, and to take notes in your essays. It is suitable for usage with underglaze paints and other glazes. It can be used in food and drink containers in application with transparent glaze. It is food safe. You can directly apply on the bisque product.