China Markers are a lab standard because they mark on almost any porous or non-porous material without scratching the surface. To sharpen simply peel for more marker.
Writes smoothly and legibly on both porous and nonporous surfaces, such as porcelain, glass, metal and plastic Peel-off china markers work on metal, glass, china and polished surfaces. Erases easily with a damp cloth. Pull string and peel down paper-wrapped strip to refresh tip. Comes in a pack of 12 yellow markers. AP-certified nontoxic. Sharpie Markers & Highlighters part of a large selection of office supplies. Sharpie(R) Peel-Off(TM) China Markers, Yellow, Pack Of 12 is one of many Specialty Markers available through Office Depot. Made by Sharpie.