Tina01
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Everything posted by Tina01
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it's an A2 drawing board , made of chipboard / MDF compressing it with rib before the final thickness is of no use and from my experience at the gaged level (~6mm) is just hiding the the problem (cracks), not solving it. They will later show up as what you've seen. it was. and the circumference of clay was certainly free. it was wrapped in two layers of very thick towels. Thank you btw, my question for now was about the cracks in rolling stage bc it had happened to me with every type of clay I have worked with so far. Two types of ready to use, one recycled and the one that is dry/raw and I'm trying to process.
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I want to try both, however now that I've found a consistent type source, need to know what am I doing wrong and what to tweak. @Babs says roll a coil around your finger, shouldn't crack. I did so and it was relatively smooth, but when making the slab it's all cracked at the bottom surface. I know there might be many factors involved, but want to know most probable ones. e.g. does it need to be mixed with bentonite, if so, how much? does it need more water? more wedging? adding temper (cattail)? should I sieve it? should I set it aside to rest after mixing with water? or should I just work on a non water absorbent material rather than wood? or something else?
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@Babs @Hulk @oldlady @Min @PeterH @JimLurking @glazenerd Can you guys please check my last post about the new clay and kindly guide me? (the one that shows coil, test title, and problem with the flattening)? TYSM. p.s. if any other photo required (from dry clay, bentonite, board surface texture, etc...) I will happily provide.
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Thank you so much! this was a great favor, I'll contact him for sure if needed. but from my past experience in arts, generally speaking it's more likely to get scientific answers from the internet, that is most "masters" try to dictate what they have learned and never doubt on their teachings, whether there might be better and more correct approaches available. Again, thank you, your time and effort are greatly appreciated.
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unfortunately not, for calcium I can ground some seashells? but still I'm not even sure that it's really bentonite, wrote its properties but nobody has confirmed yet. I was blamed for adding unwashed beach sand but shouldn't it contain (or contaminated with) calcium and/or sodium perhaps? isn't that too much? would be much more than clay itself in volume! Thank you, will try that.
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I finally found a semi-trustable source for clay unfortunately it's a one hour drive there, so I just bought ~20lbs of dry clay powder and 4lbs of bentonite clay, to see how it works. interestingly they have about the same volume. And oddly the clay is slightly greenish in color, anyone knows what it means? the bentonite one has a peculiar odor to it, is it normal? when wetting grows even larger in volume (maybe 3~4 times). in very smal quantities dries to a likely thin transparent fragile sheet of plastic. made a tile for shrinking ratio, and roughly it's 5% (went from 10cm to 9.5cm): didn't dare to mix bentonite with it, as I guessed the plasticity is fine enough: then the problem that I always have was present again: rolling the slab (6mm thickness): but the back side: if I smooth either side, the other looks like above. to reduce this I've wetted the board, it helps, but not enough. should I add bentonite clay to it? I guess about 2% right? or does it need more water, wedging, or aging (letting the wet clay sit for a week)? In addition to above, it might need some grog also (crushed breaks in 40 mesh)? I found these on digitalfire.com , 40 comes from size of sugar so I have something to compare with.
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Another failed attempt: cracks in drying time although I made my best efforts, wrapping it in two layers of thick towels. and it shrinked but there where still plenty of space if it wanted to shrink even more and not crack.
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I did try the experiment, with a lump of clay that was still not dissolved. added 1 teaspoon of baking soda in water then added the clay, it started to break: however after half an hour: then waited one more hour, but even after stirring there were some smaller lumps: and they're there now after 4~5 hours. so I repeated the process with dried pieces (they were not lumps, but pieces of my recent failure project) . Again added 1 teaspoon baking soda to one container stirred well and added the parts, left one is just water: after 15 minutes: after 1 hour, water only: with baking soda: after that, I stirred both and let them sink: I didn't notice a difference in particle size between the two while stirring and in first experiment I could achieve the same result using a mixer (for dissolving the lumps, not the cementing , if that was the problem). So, did it help? I can't judge, and let's say it did, what should I do next? adding baking soda to the dry clay powder?
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@PeterH These were pretty interesintereg! Had no idea about it! I'll try to reach more people that possibly know the regions better, however living in remote areas makes it difficult, on the other hand it's nice if I would be able to collect my own. at least I'll know what's inside! Thanks for the links! @HulkThat was interesting either! hopefully I could be able to do some research through them. Unfortunately there was no supplier in that page form Georgia, but I will keep trying, currently was able to get some workable clay (still no professional specs on them) with help of some friends. but next steps would be much more difficult! (glazes, stains, etc...) thank you! You guys are awesome!
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yes, indeed, unfortunately :-( thank you so much for your kindness! Answering my questions is a huge favor one can do for me :-) it would be easier for me to search for natural clay and process it, rather than ordering, waiting, paying for the clay, shipping, and also paying for customs (as an imported good)! Again yes, I'm so disappointed. :-( but won't just leave it.... I found the expensive white one is also available on Amazon in terra cotta https://www.amazon.com/KOH-I-NOOR-013170700000-Keraplast-Drying-Modelling/dp/B0094FZZWU/ but I can't use it as earthenware, correct? My goal is to make something functional, even just a flower vase.
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Well I found that I should buy a different brand, except for the third one which I'm not into modeling, sculptures, talking to my friends. however I tried both methods, but both are time consuming. with wetting wet, the inner region still is stiff, needs experience to know how much water is needed and may take much longer than a day depending on clay amount. with dried slices, I added water to the level that you've mentioned but they turn into thick slip so again I had to remove water, (pouring on a fine texture fabric above some folded towel). that again takes time. perhaps it's because of different clay. during that process after failure I tried to filter the clay using a strainer, and found various sizes of natural stones in 1kg (about 2lbs) of it, and guess it's abnormal and also being short, nearly worst clay possible! the ones that didn't pass: and many that passed: now I set the clay aside to drying , having no access to bentonite, what can I add for increasing plasticity? I have some iron oxide powders (red and yellow) and zinc oxide(white). will they be helpful?
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Thank you yes, sorry about the confusion! not in US, but in a small town in southern part of the country. That's why I'm so limited in availability of material and also online shopping. Also thank you for sharing your experience. I will try this either among the other method of earlier post. Unfortunately don't know anyone in person but my best guess is that those had left at the store for a long time so I will try another store. also will look if I could find a pottery workshop . thank you for your help again.
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Thank you, will try that for sure! I hope it works. Could have save me a long time and lot of work if knew that earlier.
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Thanks to everyone for their help. It seems you all agreed that adding sand caused the problem. So I threw them away and probably won't add anything in the future. As for buying clay, there's not many options to choose from, there are only 3 types available here, and the packaging is so poor quality that they are just softer than leather hard and wedging them is quite hard. I don't know how others deal with it and wonder what to do with them? 1. Normal, raw wild clay (perhaps with some processes). 2. Clay mixed with a plant called Typha latifolia, (bulrush?) advertised to be more crack resistant than the regular one. 3. White, air dry clay, that is very expensive. better packaging, softer, but I guess it's only for sculptures and not firing. And there's no cone or any other info available. I bought all, however don't know how to properly add back water to them. Is making a slab and submerging in water or forming to a bowl then pouring water in it is a good idea? Thank you again everyone!
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No, actually the clay was dried (not used from purchase time , I don't have access to raw or wild clay if that's what you mean). So I really don't know if it already has something in it or not. I guessed not, therefore added the sand. It was not recommended or special, as I mentioned, just picked them up from a beach. Oh about the silica, didn't know that either, the guy on youtube says add sand, wood ash, crushed fired clay, etc... for absorbing thermal shock... yes... I won't add anything more to the currently recycling batch and also will compare it with new ones I should buy. When it is percent, how does it differ if it's a small pot or big? except for these additions to handle thermal shock, what can I add for increasing plasticity and avoid cracking in drying and firing time?
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the small cracks on the outside yes, although I knew it won't help and they shouldn't appear in the first place. What is visible in photo are from those on the bottom side (on the mold). Yes, that was disappointing so I removed them and added back to the rest of chunk with a little water stored in a plastic bag.
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Yes, you're right, I should have test it but since adding sand was more easier to clay/water mixture in bucket than to the clay later, I did that. The sand was not washed (if you mean by tap water) I really can't tell the mesh size, but I collected them from the beach (will attach a photo) . The most weird thing is if they clay is too wet, it will be sticky but shouldn't crack. However mine was cracking while shaping, flattening, bending... not only at edges but all over the slab. leaving it to dry and wedging helped a lot, but still far far from a regular workable clay. By the way, why there are some lumps still in the bucket and it's not uniform after 6 days? I hardly think that those disolve at all. the lumps sand grains, pencil for reference
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Well mine was a bit wetter and more sticky but it was cracking at the same time.
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The clay was not fired or anything, just had dried in its packaging. I crashed the blocks to the size of golf ball chunks (more or less) then put them in a bucket, filled with water. After 4~5 days and stirring everyday , there were still a few lumps not dissolved in it but I didn't pay attention to those. Then according to some recipes I mixed about 20% sea sand to it and put it in a pillow case to dry. I have another bucket with same clay sitting for a week now, but still it has some clay lumps in it, I guess I should use an electric mixer. But for current batch I'm not sure if it's because of added sand or not. I can't pull them out so either I have to discard it and don't add anything to the new bucket, or if sand is ok redo the wetting procedure again as you told? p.s. No, they are just regular clay (not a well-known manufacturer or brand) but I'm sure they're good as I've seen people use the same without problem.
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Hi I'm Tina and just joined here, I'm a total newbie in pottery. I had some clay that were bought a couple of years ago, obviously they were bone dry. I attempted to recycle them and start making something. However it didn't go well. The problem is that although the clay was wet and sticky (to wooden board and my hands), at the same time many small cracks were forming when I tend to flat it with a rollor. or making a coil out of it. I tried to wedge it for half an hour, adding a bit more water, but that didn't help much. small cracks all over the slab and more severe cracks around the edges. what could be wrong with it and what should I do? more info with pictures: Thank you so much for helping me!
