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The best overall choice for grinding media is Lead. Due to its heavy weight, it grinds chemicals & powders quickly and efficiently. If you are milling Black Powder, Lead is the only media you can use as it is completely non-sparking. Using either steel or ceramic media when milling Black Powder will cause an explosion. If you plan on grinding very hard materials (such as Glass particles) it is recommended that you use Steel media as it is both hard and heavy. When grinding Glass and similar hard substances, your starting material should be about as coarse as ordinary sand. The Ball Mill with then reduce it to a fine powder. Due to its small barrel diameter and lower impact energy, the 3 pound mill is not suitable for grinding Glass or similar hard materials.
Ceramic media is a good choice when you must keep your media contamination to an absolute minimum. However, because of its light weight, ceramic media can take considerably longer to produce desired results.
Contamination: If you are doing high purity work and are concerned with contamination from the barrel, several customers report they get good results by placing the media and material to be ground into a heavy (freezer type) zip-loc baggie, then placing the baggie in the barrel. The material will be ground and reduced to a powder within the baggie and never comes in contact with the barrel itself. Get beneficiation,Mineral Processing,rotary kiln From http://www.ballmill8.com