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Gokul

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  1. Is there any scientific way of measure the plasticity and tell it in numbers ? I know the easy way by rolling out a coil and wrap around the fingers to check the plasticity in no time but I wanted to know is there any way that I can measure it and keep noted so that it can be a reference is future ...
  2. Gokul

    Glaze Bilsters...

    Tom, The colour in the foot ring is because of the carbon coring or its because of the sulphides which causes the colour ? Also we are using the same ball clay for our glaze as well but i dont know this particular glaze has ball clay in it., And even if its because of the sulphides and carbon wi is it not happening with all the glazes happening with only the particular glaze ?
  3. Gokul

    Glaze Bilsters...

    Yes, I ll cut down the soak to 15mins and see hows its coming., Yes the glaze application is thick as well and does the thick application cause these kind of craters and bilsters ?
  4. Gokul

    Glaze Bilsters...

    We are using the hold for the glaze to even out and the body to mature well.
  5. Gokul

    Glaze Bilsters...

    Min, Here is the chemical of the ball clay which we are using.
  6. Gokul

    Glaze Bilsters...

    But Tom, We are not adding any red clay (Laterite) to our receipe, but still its pinholing and blistering...
  7. I have this heavy blisters and pinholes issue and I m doing the Bisque at cone 08 and glaze temperature is at cone 6 + 40 mins soak., Whats the reason behind this blisters and pinholes ? Is it a clay issue or its something to do with a glaze chemistry ?
  8. Babs, I have been try using the synthetic plasticiser to the clay and can share you the results once the clay is ready.
  9. Babs, The crack is happening in the mold itself but it not a end to end crack and its a surface cracks but bit deeper than the usual surface cracks.
  10. Rae, yes we have try adding 5-20% grog to the body but still the cracks are happening in the same area. :-(
  11. Hi, We have been doing the jigger for the first time and the pieces whatever we are making have a cracks in a same pattern in a same location, and we are using Terracotta clay to make the pieces and here I m attaching the cross sectional pieces of the molds., and in the molds I have few doubts and I would like to get clarified so that I can reduce the cracking doors one by one., Does the thick and thin portions of the molds absorbs water differently so that the pieces are cracking ? As you can see the picture of the pieces the cracks are happening in the place where the side wall is connecting with the curved edges, and the cracks are happening only with our terracotta clay and we have tried quite a lot of receipes to avoid cracks but nothing is helping out and the cracks are happening in the inside of the pieces and the outside wall is just fine. Also we have tried jiggering few pieces with our stoneware clay and we havent have any cracks in the stoneware. Does the uneven wall thickness is the reason to get the cracks ? Wi only the Terracotta is cracking and not the stoneware ? Wi the inner wall is cracking and it didnt extend to the outer wall ? Does it anything to do with the plasticity and the composition of the clay? As far as the design is concerned, we make sure theres no undercuts in the design and even the wall is not striaght and it has an angle of 10% for easy releasing., we used to have few issues with our clay body which I was working with Tom (Glazenerd) to solve the issue, but apart from that I would like to know what are the other possible reasons for the cracking.
  12. Tom, Pls find the attached picture of the clay which we are blending and using., These are the two red clays which we are getting from our supplier No.1 Red one seems like the laterite or red soil after I read the article of Dr. sudharsans article abstract and the No.2 seems like more of an alluvial soil I guess so, and we used to get the No.2 most of the time becasue it used to be very good interms of plasticity and there wont be any cracking as well but the No.2 Mines clay is not easily available I can get the material only at the time of summer because the mines will be closed at the time of Mansoon. So we cant and we dont want to rely on the brown one itself then we got the red one (No.1) which is very fine interms of particle size distribution and it has less plasticity ., so right now what we are doing is we get a stock of No.2 clay as and when its available and we mix 50% of No.1 and 50% of No.2 clay and we do our processing and make it into a clay. But still we have the cracks issue so we started adding 1% Sodium Bentonite with the above mixture mentioned and we make it as clay and pug it using the pugmill (Pic Attached) its a deairing pugmill but it dosent have any vacccum attached it and its a good homogeniser. Pls find the attached pic of the process flow chart of our clay making process. And the WOPT of our clay is 23 %. Dry Shrinkage - 6 % Fired Shrinkage - 8% @(cone 08) LOI - 15% @(cone 08) Porosity - 20% @(cone 08) Pls find the wet sieve analysis result below of the two clays Sieve No No.1 No.2 40 0.1 0.2 60 1 0.7 80 2.2 2.5 100 3.8 4.9 120 3.2 3.9 140 7 9.8 170 8 11.1 200 11.2 30.4 230 12.9 15 270 8.7 2.1 300 15.2 15.7 PAN (300+) 26.7 3.7 Total 100 100
  13. Curt, Thanks for your reply, and the top picture is our regular terracotta which is been throwing on the wheel.
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