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Showing results for tags 'absorption'.
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I recently pulled out my first mugs from a cone 6 firing. I used Draycott Stoneware from Potclays, UK and fire in oxidation to 1050 degrees c slow bisque and 1222 in a glaze firing, slow cooling to achieve matte surfaces with my glazes. I glazed the inside of the mug with a commercial transparent glaze from Scarva pottery supplies (so unsure of the CTE) and the outside of the mug with a satin matte glaze that has a CTE of 6.5. After a week of test using the mug (pouring boiling water I know will have exacerbated the problem), 2 big hairline cracks appeared on the inside of the mug. I smashed the mug apart to check the throwing thickness to see if there were any thin spots in the walls that may have been put under stress and cracked but the thickness seems to be pretty even and consistent. I know potentially the problem could be mismatching CTEs of the liner glaze and the outer glaze and so I am now mixing up my own transparent glossy liner glazes to regain control over that process - but my question is how closely matched do the inner and outer glazes have to be in terms of CTE? Could the problem be that they don't match the body? and looking at my firing temps and process - could the mug be under fired and allowing water to seep in through the unglazed footless bottom surface and placing inner stress on the clay? Am I missing something? Any advice greatly appreciated!
On a recent Clayflix tutorial by Lisa Naples she mentioned she fires her earthenware to cone 1 or 2, which reduces the water absorption rate by a huge amount and renders the clay almost vitreous. Does anyone have experience with this and, if so, what clay do you use?
Hi guys, I am looking to make a multiple piece mould (imagine I'm casting coke can's and want to make a mould that casts 6 of those coke cans at once). It would be a one piece mold, as in one piece of plaster like a brick with 6 holes in it and a 'plate' piece underneath it. Would this cause an issue to cast 6 masters assembled like a grid, in terms of how the water absorbs into the plaster? ie. With two placed next to each other, would the water absorb through and clash with the water being absorbed from its neighbour? Any help would be great! Cheers.