Celia UK Posted June 16, 2016 Report Share Posted June 16, 2016 Celia: I find it very hard to believe this clay matures at 1200C [ 2192F] The silica % is lowered, which is the usual protocol for cone 10 to prevent dunting due to free silica/cristobalite formation. The alumina is on the low side as well for a stoneware body- more in line with earthenware. The primary flux is potassium: which is in line with cone 8-9 range. Some comparisons: Generic C10 stoneware body: 64.97 silica, 28.31 alumina, total fluxes: 3.71 >> I would estimate the maturing temp of the body shown above in the cone 8-9 range at minimum. (total fluxes 3.81%) Iron can only be counted as a flux if it is fired in reduction. Nerd It was Scarva's reply to a customer's question that said it matures at 1200oC - I didn't find that anywhere else and haven't heard it from Vaentines. With my limited knowledge, the ingredients mean absolutely nothing to me, but I guessed it would be informative to some of you out there! I have to say, I always thought of a firing 'range' as the range within which it would be 'cooked'! - mature from the lower temperature upwards with a risk of melting beyond the upper! Even if there is a wide range, also giving the maturing temperature would help - or does this actually depend on heat work rather than actually being a fixed point temperature???? Why is it that in the UK clays and glazes are given temperature ranges and in the U.S. are more often given 'cones'? With the digital controllers on both my kilns using degrees centigrade, I have an ongoing mental exercise getting my head round the correlation between temperatures and heat work (cones). I've got all the charts and so know the theory, but then, there's what my kilns actually do..... I've been quite envious when reading posts that say e.g. 'I programmed my kiln for Cone 5 - 'fast''. Makes it sound so straightforward. Link to comment Share on other sites More sharing options...
Babs Posted June 16, 2016 Report Share Posted June 16, 2016 I think you can program the kiln at cone 5 fast but unless you have tested this against actual cones in the kiln to verify this it is an assumption. Different loading etc may mean that the kiln actually reached cone5 or part of it etc. Same as you seting it for a specific temp fast firing may bring you the results you want or not. Sorrynot very clear... Link to comment Share on other sites More sharing options...
Joe_L Posted June 16, 2016 Report Share Posted June 16, 2016 Celia: Valentines and Scarva websites both state "ES 10 matures between 1160°C - 1280°C." Quite a lot of commercial clays seem to be advertised with very wide ranges - whether you trust it or not is another matter. Oly: It's interesting your 1210/15min soak firing leaves the clay porous. My 1220/20min soak seems ok. How fast was your temperature rise towards the end? Mine was 130C/hr with Cone 8 well down (more than I was expecting). Link to comment Share on other sites More sharing options...
PottaFella Posted June 16, 2016 Author Report Share Posted June 16, 2016 Celia: Valentines and Scarva websites both state "ES 10 matures between 1160°C - 1280°C." Quite a lot of commercial clays seem to be advertised with very wide ranges - whether you trust it or not is another matter. Oly: It's interesting your 1210/15min soak firing leaves the clay porous. My 1220/20min soak seems ok. How fast was your temperature rise towards the end? Mine was 130C/hr with Cone 8 well down (more than I was expecting). 100°C per hr to 600°C 150°C to 1210°C 15min soak it then takes c12 hrs to cool down glazed with matt glaze as in my original post leaves it somewhat porous. Link to comment Share on other sites More sharing options...
Sputty Posted June 16, 2016 Report Share Posted June 16, 2016 . Link to comment Share on other sites More sharing options...
glazenerd Posted June 17, 2016 Report Share Posted June 17, 2016 Celia: The real chemistry answer will just make it worse. We view temperature in degrees or celsius: how hot something is. Temperature is actually the measurement of how fast atoms are moving. So that would make your kiln a particle accelerator. Nerd Link to comment Share on other sites More sharing options...
PottaFella Posted June 17, 2016 Author Report Share Posted June 17, 2016 The refiring has worked - the pot is no longer weeping - however, my subtle cream/white matt glaze is now somewhat darker and glossier. Link to comment Share on other sites More sharing options...
Celia UK Posted June 17, 2016 Report Share Posted June 17, 2016 So you win some and you lose some Oly - at least you have a functional pot now! Link to comment Share on other sites More sharing options...
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