mrichter Posted August 21, 2010 Report Share Posted August 21, 2010 I have some experience with clay-have a kiln and have always fired to cone 6. With this particular project I plan on making a simple two part mold and pour slip in to it. I want the completed piece to have the strength and hardness of river rock. Can you help me make right choices here in choosing the clay and firing temp., etc? SouthernArtistry.org/Marsha_Richter Link to comment Share on other sites More sharing options...
Seasoned Warrior Posted August 22, 2010 Report Share Posted August 22, 2010 I have some experience with clay-have a kiln and have always fired to cone 6. With this particular project I plan on making a simple two part mold and pour slip in to it. I want the completed piece to have the strength and hardness of river rock. Can you help me make right choices here in choosing the clay and firing temp., etc? SouthernArtistry.org/Marsha_Richter Strength typically is specified as two types, tensile and compressive. Which in particular are you looking for? Typically river rock runs about 3ksi compressive strength while the tensile strength is substantially less and depends on the specific physical type and chemical composition of rock we are discussing. Some rocks are amorphous and others are crystalline. The crystalline types fracture differently along different planes, some fracture more easily than others. Hardness is typically defined in Mohs which is an arbitary comparative scale using different types of stones as a reference. The lowest Mohs scale is the hardness of talc and the the hardest is diamond. There is a huge difference between hardness and strength; while diamond is hardest it is not a particularly strong stone and readily fractures perfectly along crystalline planes. There is another measure of hardness and that is resistance to abrasion. Also one other consideration is toughness which is resitance to impact. What properties are you actually looking for and how do you define them? Both the American Concrete Institute (ACI) and the American Society for Testing and Materials (ASTM) have extensive specifications for rock which might give you a good insight in the properties you are looking for. Ceramics includes a wide variety of materials besides what we normally refer to as "Clay" and you may be able to specify a ceramic material that more closely approaches or exceeds the specific properties you are looking for. best regards, Charles Link to comment Share on other sites More sharing options...
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