Why my clay acts like this?

[Tina01]

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! 

[Babs]

The mold ,steel bowl  , needs to be coated with something to prevent clay from sticking to it as it dries.

Strips of damp newspaper, plastic wrap, green thick dishwashing liquid etc.

Oh! a hump mold  need to get that clay off there asap. Clay shrinks, mold doesn't

How did you wet the clay  down?

Was the clay previously thrown into pots? Can lose fine particles which make clay plastic.

Make a slurry of clay   leave for a couple of days, spread out on plaster board to dry , wedge and see if it is better.

May need some bentonite to increase plasticity.

Do you know what clay it is?

Edited October 20, 2022 by Babs

[Tina01]

1 hour ago, Babs said:

The mold ,steel bowl  , needs to be coated with something to prevent clay from sticking to it as it dries.

Strops of damp newspaper, plastic wrap, green thick dishwashing liquid etc.

How did you wet the clay  down?

Was the clay previously thrown into pots? Can lose fine particles which make clay plastic.

Make a slurry of clay   leave for a couple of days, spread out on plaster board to dry , wedge and see if it is better.

May need some bentonite to jncrease plasticity.

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. 

Edited October 20, 2022 by Tina01

[Hulk]

I like recycled clay!
It's a bit of work, on the other hand, the material is "free."
I'm bagging the clay when it is just a bit wetter/softer than what the vendor provides, however, not so wet that it's very sticky - I can wedge it without having to then scrape off my hands, and although some bits stick to the wedging board, it's not much.

[Jeff Longtin]

My hunch is that there is too much sand in the clay.  I would have suggested you test the clay first before adding that much sand. 

Has the sand been washed? I've never worked with sea sand but I wonder if it adds salt to the clay? Do you know the mesh size of the sand? A smaller mesh would have less impact on plasticity. 

 

[Tina01]

1 hour ago, Hulk said:

I like recycled clay!
It's a bit of work, on the other hand, the material is "free."
I'm bagging the clay when it is just a bit wetter/softer than what the vendor provides, however, not so wet that it's very sticky - I can wedge it without having to then scrape off my hands, and although some bits stick to the wedging board, it's not much.

Well mine was a bit wetter and  more sticky but it was cracking at the same time.

[Hulk]

I'd missed the percent sand.
Now I'm curious how my clays would behave with twenty percent sand added.

Looks like you smoothed those small cracks over.
The big cracks, do they still appear when the piece is allowed to shrink - removed from the mold sooner?

Edited October 20, 2022 by Hulk
typo

[Min]

5 hours ago, Tina01 said:

I mixed about 20% sea sand to it

I wouldn't do this until you have fired some test tiles to see what the sea sand is doing to the clay. If it contains calcium (from seashells) it could really affect the firing. Also 20% sand is a lot for making small(ish) pots like in your example.  I'ld suggest starting from the beginning and making some tests with 5%, 10% and 15% sand. Wash the sand, dry it then weigh out the amounts and add it do dry clay and slake it down, mix it up with a paint mixer then when workable make some test tiles and fire those (with no glaze) to whatever cone the clay is rated for then examine the test tiles.

Was it sea sand that was recommended to you or just "sand"? In ceramics when sand is mentioned it's silica sand. Silica sand comes in different mesh sizes, the smaller the number the courser the sand.  

I'ld also try making some pots without any added sand, clay might be just fine the way it is.

[Tina01]

48 minutes ago, Jeff Longtin said:

My hunch is that there is too much sand in the clay.  I would have suggested you test the clay first before adding that much sand. 

Has the sand been washed? I've never worked with sea sand but I wonder if it adds salt to the clay? Do you know the mesh size of the sand? A smaller mesh would have less impact on plasticity. 

 

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

 

[Tina01]

34 minutes ago, Hulk said:

I'd missed the percent sand.
Now I'm curious how my clays would behave with twenty percent sand added.

Looks like you smoothed those small cracks over.
The big cracks, do they still appear when the piece is allowed to shrink - removed from the mold sooner?

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. 

[Tina01]

1 hour ago, Min said:

I wouldn't do this until you have fired some test tiles to see what the sea sand is doing to the clay. If it contains calcium (from seashells) it could really affect the firing. Also 20% sand is a lot for making small(ish) pots like in your example.  I'ld suggest starting from the beginning and making some tests with 5%, 10% and 15% sand. Wash the sand, dry it then weigh out the amounts and add it do dry clay and slake it down, mix it up with a paint mixer then when workable make some test tiles and fire those (with no glaze) to whatever cone the clay is rated for then examine the test tiles.

Was it sea sand that was recommended to you or just "sand"? In ceramics when sand is mentioned it's silica sand. Silica sand comes in different mesh sizes, the smaller the number the courser the sand.  

I'ld also try making some pots without any added sand, clay might be just fine the way it is.

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? 

Edited October 20, 2022 by Tina01

[Babs]

Crack the dried clay down as much as possible snd then slake.

Sand is your prob.

If already a handbuiling clay ,dnt need it. Coil abit of clay and bend the coil around your finger, shouldn't  crack.

[Callie Beller Diesel]

Some white firing clay bodies, especially some mid-fire porcelains,  don’t reclaim well unless you have all the components added back into the mix.  IThat’s because some of them have neph sye as an ingredient, which is slightly soluble, and it affects thixotropy and plasticity. If you add or subtract too much, it can make your clay extra short. Because you’re reclaiming clay that hasn’t been used, I don't think this is your problem, and drying the batch that doesn’t have the sand added will confirm or disprove that.

BUT. 

If you didn’t wash the sand and it was from an ocean beach, there could be any number of possible solubles that will also mess with that particular point of chemistry. If your clay body is one of these clay bodies that doesn’t like to be reclaimed AND you added extra sodium or calcium solubles left behind by sea water, that would also explain this reaction. Especially because you let the slurry sit for a few days, and everything had a really good chance to marinate together. 

[Tina01]

 

On 10/20/2022 at 11:36 PM, Babs said:

Crack the dried clay down as much as possible snd then slake.

Sand is your prob.

If already a handbuiling clay ,dnt need it. Coil abit of clay and bend the coil around your finger, shouldn't  crack.

 

On 10/21/2022 at 9:16 PM, Callie Beller Diesel said:

Some white firing clay bodies, especially some mid-fire porcelains,  don’t reclaim well unless you have all the components added back into the mix.  IThat’s because some of them have neph sye as an ingredient, which is slightly soluble, and it affects thixotropy and plasticity. If you add or subtract too much, it can make your clay extra short. Because you’re reclaiming clay that hasn’t been used, I don't think this is your problem, and drying the batch that doesn’t have the sand added will confirm or disprove that.

BUT. 

If you didn’t wash the sand and it was from an ocean beach, there could be any number of possible solubles that will also mess with that particular point of chemistry. If your clay body is one of these clay bodies that doesn’t like to be reclaimed AND you added extra sodium or calcium solubles left behind by sea water, that would also explain this reaction. Especially because you let the slurry sit for a few days, and everything had a really good chance to marinate together. 

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!

Edited October 23, 2022 by Tina01

[PeterH]

2 hours ago, Tina01 said:

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? 

This sort of idea is often recommended:
https://www.clayartcenter.org/clay-art-center-blog/2020/3/how-to-rehydrate-bone-dry-clay-easily

Video of the same idea on a slightly smaller scale:

 

[oldlady]

tina, could you please identify your location for us?   i do not think you are in the United States but in the country of Georgia.   that makes a very important difference so we do not give you information you cannot use.

from experience, i learned that trying to wet clay that is already partly wet does not work.     drying out the clay in thin slices works very well.   once the clay is totally dry, the water you add will immediately be sucked up and the clay will soften.   if the clay is not totally dry it will not work.   left overnight, the clay you have wet will be usable the next day.  i do this in a bucket and collect dry bits as i work each day.   when i want to use it, i add the water to just above the dry clay and let it soak in overnight.

if you know of people who use this clay, talk directly to them to ask what they do.

[Tina01]

2 hours ago, PeterH said:

This sort of idea is often recommended:
https://www.clayartcenter.org/clay-art-center-blog/2020/3/how-to-rehydrate-bone-dry-clay-easily

Video of the same idea on a slightly smaller scale:

 

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. 

[Tina01]

1 hour ago, oldlady said:

tina, could you please identify your location for us?   i do not think you are in the United States but in the country of Georgia.   that makes a very important difference so we do not give you information you cannot use.

from experience, i learned that trying to wet clay that is already partly wet does not work.     drying out the clay in thin slices works very well.   once the clay is totally dry, the water you add will immediately be sucked up and the clay will soften.   if the clay is not totally dry it will not work.   left overnight, the clay you have wet will be usable the next day.  i do this in a bucket and collect dry bits as i work each day.   when i want to use it, i add the water to just above the dry clay and let it soak in overnight.

if you know of people who use this clay, talk directly to them to ask what they do.

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.

[Tina01]

On 10/23/2022 at 5:42 PM, oldlady said:

 drying out the clay in thin slices works very well.   once the clay is totally dry, the water you add will immediately be sucked up and the clay will soften.   if the clay is not totally dry it will not work.   left overnight, the clay you have wet will be usable the next day.  i do this in a bucket and collect dry bits as i work each day.   when i want to use it, i add the water to just above the dry clay and let it soak in overnight.

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? 

Edited October 28, 2022 by Tina01

[oldlady]

oh!  that is very bad stuff, i do not want to call it clay.    seeing it makes me feel like i should send you some good clay but i cannot afford the shipping costs.   is there any other country that you can buy clay from?

there is no future in trying to work with whatever that stuff is.   you just must find a clay source that has real clay.   does your country have an art program in a university?   if so, maybe you can find their supplier and buy from them.

wish you good luck finding clay.

[LeeU]

On 10/23/2022 at 9:33 AM, PeterH said:

This sort of idea is often recommended:

@Tina01--PeterH is showing you what I find to be the best and easiest way to rehydrate clay.  It's kind of a "no fail" method (I learned about it here on this Forum) and I use it for up to 25 lbs of clay in a 5 gal. bucket.  Check it out!

[Tina01]

12 hours ago, oldlady said:

oh!  that is very bad stuff, i do not want to call it clay.

yes, indeed, unfortunately :-(

12 hours ago, oldlady said:

seeing it makes me feel like i should send you some good clay but i cannot afford the shipping costs.   is there any other country that you can buy clay from?

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)!

12 hours ago, oldlady said:

there is no future in trying to work with whatever that stuff is. 

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.

[PeterH]

In case it's of any help: Clays of Georgia for Ceramic Applications
http://gspltd.ge/admin/editor/uploads/files/InterCeramics.pdf

No experience in looking for clay myself, but perhaps these are of interest:
Where is Clay Found? https://ancientpottery.how/where-is-clay-found/
How to Find Clay, the Definitive Guide  https://ancientpottery.how/how-to-find-clay/

But if you do have a commercial source of real pottery clay, that seems the easiest option. Even if you have to re-hydrate it.

[Hulk]

Isn't Georgia known for white clay?
Perhaps pottery shops in Georgia could direct you to suppliers.

Some may carry supplies! For example, the MODI Ceramic Project in Tbilisi, who feature Seramiksir products
MODI ceramic shop

This shop's website mentions Georgian white clay, " The business prides itself on being the first studio to develop and produce the acclaimed Georgian porcelain..."
About us – White Studio
 

Here's a listing of global suppliers, interesting!
Ceramic Materials Suppliers — pottery to the people

[Tina01]

@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!