99.9% Graphite. select the size you need, and there is a little measurement tolerance(0-0.3MM) Excellent thermal conductivity and corrosion resistance. Melting and casting metals such as Gold, Silver, Brass, Aluminum, Copper, Zinc, Plumbum, etc. Pure graphite crucible can NOT be heating by carbon furnace or charcoal kiln. It will be oxidized and cracked; Pure graphite will start to oxidize at 752 °F （400℃). The withstand temperatures can be 3200 °F if you use Air Electric Furnace. The withstand temperatures can be 5000 °F if you use Vacuum or Gas Protection Furnace. Keep in dry place, After drying the crucible, please avoid the water. Be careful not to give a mechanical impact force, not from a fall or impact. OTOOLWORLD 99.9%Pure Graphite Crucible Metal Melting Gold Silver Scrap Casting Ingot Mould