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How To Test Clay


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so pretty soon i am going to be off on an adventure to try out different clay bodies from the different makers of clay ^5/6 available on the west coast.

 

how do i make the judgement. i am fairly new at this. started about a year back at a community college, but have thrown a significant amount. 

 

i love throwing with Bmix with grog ^5. except for plates i have thrown many different pieces. never had a problem with B mix with grog. but it is temperamental.

 

so how do i figure out if the clay is NOT temperamental? what should i look out for? is it going to be time that's going to tell me? the appearance of cracks, kiln issues?

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Clhoosing clay is kind of like picking a set of flaws you can live with, and it's also an area you have to exercise you own taste or preferences. It's ok to change your mind. What qualities do you like about the clay you work with, and what problems do you need fixed? Then ask for recommendations from your supplier. They'll have reports from their customers on how things behave in a general fashion. After you pick a few likely candidates, make your work out of at least a full box to see if it'll meet your demands from formed to finished. Reserve judgement until you have finished pieces in front of you.

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Here is how I did it:

 

1. Pick a color. For me it is a non-pure white.

2. Highly functional work? If yes, pick one that has low absorption.

3. Buy a bag of everything that seems to meet these needs.

4. Try a little. Guess which one you like the most.

5. Don't second guess.

5. Buy a ton.

 

Based off what you wrote, I suspect you would be happy with Newcomb 6. I am happy with it for non-temperamental and easy enough to throw reasons. My students have had no complaints and no compression issues too. I don't know the range of availability, I get it from the Clay Art Center in Tacoma, WA.

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oh thank you guys. this means so much to me. i am learning sooo much from you all and just the attitude and philosophy to approach things.

 

i would not have even changed or thought of clay if it wasnt for this forum. but at school my attention was drawn to lots of S cracks and round cracks amongst advanced students in any plate and plate like forms like big shallow bowls, planters and platters. made me wonder why we saw so many cracks. 

 

i have decided instead of going to our local clay store i am going to go to the local clay factory store IMCO (whose clays are not carried at our local clay store). since i will be focusing on 'naked clay' i have on my list different coloured clays that are all ^5/6. there are quite a few choices i have. Marcia i have already read the descriptions and decided which ones i would like to try. i have even looked at their absorption levels. i have selected about 6 different clay bodies to try out. 

 

from what fellow students have told me the staff at IMCO are not as well informed. for our ^5 studio students have come back with ^10 clay as the factory store said that was the best clay. 

 

i am looking forward to all the trial and errors. 

 

last semester i threw a bag of  cassius basaltic. i loved that clay body and with my uber failed pieces i learnt a lot and learnt to love that clay and realized what a criminal act it was to cover that beautiful claybody in glaze even though it did WONDERFUL things with the glaze (but too much bloating). so i learnt my lesson and learnt how to use it in our kiln's regular schedule as i could not change the firing. eventually i did have some successful pieces.  

 

and this last week a threw a bit with quyle's sierra gold and love the look of the clay. threw well. its a cone 10 clay that someone in class wanted me to try out. 

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i would not have even changed or thought of clay if it wasnt for this forum. but at school my attention was drawn to lots of S cracks and round cracks amongst advanced students in any plate and plate like forms like big shallow bowls, planters and platters. made me wonder why we saw so many cracks.

Hi Preeta:

Do not base your clay choice on rather the pieces come out with cracks. Base it on how it throws and works for you. The glaze can be adjusted to ft your final clay choice. Any clay that has a broad range of firing temps, I am leery of..Cone 10 clays requires less flux, and normally uses less silica than a cone 6 clay for several technical reasons. That said, I find it nearly impossible that a clay body could be blended to mature correctly at the lower end, which means it would have equal problems at the higher end.

I would however do one test as your are figuring out your clay of choice. Do not need to be too technical because COE and shrinkage should have been determined by the maker. I would make a 4 x 4 tile and fire it unglazed to maturity: then weigh it and chart. Then boil it for 2 hours, pat dry, and weigh it again. If their is a difference, that means it is absorbing water, which also means it has not fully vitrified. If you are doing functional ware: this could be a problem.

Nerd

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thanks Bruce. I had no idea Laguna sold packs like that. I am going to ask IMCO if they have the same thing as Laguna. 

 

Glazenerd now i understand from the platter broke in half thread all the issues with cracks and why you are saying not to judge from cracks. 

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