Why my clay acts like this?

[Tina01]

@Babs @glazenerd

I conducted a PH test, Don’t know if it's useful or not but hopefully it will as it took 2 days!

I didn't have a fancy test kit so I used a red cabbage : D but tried to be as precise as possible. 

01) The amount used for each test.

Then I added 1/2 tablespoon of following materials, stirred well, then added water to 100ml, let that sink if it was required. 

02) HCl , diluted, strongest I could find.

03) Vinegar 

04) Tomato

05) Colorless soft drink 

06) Water

07) Old red recycled clay 

08) Current clay 

09) Egg 

10) Baking soda (saturated water)

11) Bleach 

So I think:

The new clay is more alkaline than old one but not much, it could be around 7.4 or7.5 ( calculating this value with normalization, if the original indicator be of any PH value,  still best approximation for water is 7 and egg is certainly 7.8) Then it falls between these values. 

 

[glazenerd]

Tina:

I made some assumptions based on the information you have provided so far.  I also converted to metric-

1/4 Liter of clay = 220 grams +/-

add 5grams of bentonite ( or 5ml ) My bentonite came out almost exactly 1 gram = 1 ml.

Add 1 teaspoon of baking soda to 1/4 liter of water and shake well (stir). Then pour off 60 ml of water only; to be used in the clay. Do not allow any residue from the baking soda into the clay.  The actual amount of water needed to form a clay ball should be around 50 grams.

Once you blend into a pliable ball: let it stand 3-5 days before checking plasticity. Plasticity is not automatic: it builds up to a peak over a period of days.

This is a base recipe/starting point: may need adjusted as you check plasticity levels. Once you reach a workable formula: simply multiply the base to make larger batches.

*** had to hijack my wife's computer; my 16 yr old Ipad is on its last leg.

Tom

[Tina01]

7 hours ago, glazenerd said:

Once you blend into a pliable ball: let it stand 3-5 days before checking plasticity. Plasticity is not automatic: it builds up to a peak over a period of days.

Thank you so much Tom.

I guess the water was a bit low, instead of 60ml I added 70ml but didn't go further as you should've calculated it correctly. 

220g clay + 5g bentonite 

after adding 70ml of water/baking soda solution:

nowhere near pliable. after much wedging kneading compressing, best ball shape:

so put it in a plastic bag and sealed for further diagnosis and remedies .

[Babs]

5 hours ago, Tina01 said:

Thank you so much Tom.

I guess the water was a bit low, instead of 60ml I added 70ml but didn't go further as you should've calculated it correctly. 

220g clay + 5g bentonite 

after adding 70ml of water/baking soda solution:

nowhere near pliable. after much wedging kneading compressing, best ball shape:

so put it in a plastic bag and sealed for further diagnosis and remedies .

I'd dip that in water then put in plastic for a while.

[glazenerd]

Tina

Bentonite can absorb up to 15 times its weight in water. So adding 70 ml does not come as a surprise. from what I see, looks like your in the 75ml range total. The main thing is to keep records as you go. Be sure to mix clay and bentonite well before adding water.  Additional note: powdered clay has silica: mix outside if you can- wear a mask until you get it moist.

Tom

[PeterH]

I wonder if these ideas could simplify the incorporation of bentonite into the mix

How to Add Bentonite to a Wet Glaze
https://suemcleodceramics.com/how-to-add-bentonite-to-a-wet-glaze/

[Tina01]

12 hours ago, Babs said:

I'd dip that in water then put in plastic for a while.

sure, but didn't want to change the formula that Tom had calculated with much trouble...

7 hours ago, glazenerd said:

Bentonite can absorb up to 15 times its weight in water. So adding 70 ml does not come as a surprise.

Thank you Tom and sorry again for the troubles, hope you've read my message. I know  that about bento, that makes me think if I add 75ml ~= 75grams water/bs to the mix, all the water will get absorbed by bento (5g x 15 = 75) So what will remain for the clay itself? 

7 hours ago, glazenerd said:

The main thing is to keep records as you go. Be sure to mix clay and bentonite well before adding water. 

I am and hope they stay on this site also, they might be useful for someone else. 

Yes, I  did so, but didn't know have to wear a mask.

7 hours ago, glazenerd said:

from what I see, looks like your in the 75ml range total.

Added 10ml more water as a total of 80ml. flattening it inside ziplock bag hopefully to get into the body.

still it's confusing that bento eats all so no water will mixed with clay even if bento dispersed evenly inside body. or perhaps I'm wrong. 

 

6 hours ago, PeterH said:

I wonder if these ideas could simplify the incorporation of bentonite into the mix

How to Add Bentonite to a Wet Glaze
https://suemcleodceramics.com/how-to-add-bentonite-to-a-wet-glaze/

That was interesting, though I doubt it works! mine will probably just clog the top of the tube! I will try that anyway. 

TYSM all!

Edited November 13, 2022 by Tina01

[Babs]

57 minutes ago, Tina01 said:

 

That was interesting, though I doubt it works! mine will probably just clog the top of the tube! I will try that anyway. 

TYSM all!

It does!!!!

Use another container and decant into tube after slaking overnight or till it reaches the state Sue describes.

Many folk have a bentonite "slurry" premixed as Sue McLeod  blogs about sitting near their reclaim bucket or in their glaze mixing area.

[Tina01]

On 11/14/2022 at 1:21 AM, Babs said:

It does!!!!

Use another container and decant into tube after slaking overnight or till it reaches the state Sue describes.

Many folk have a bentonite "slurry" premixed as Sue McLeod  blogs about sitting near their reclaim bucket or in their glaze mixing area.

Well something is wrong, I did that, as she was stated, tried to  sprinkle bentonite on water and not touch that. Mine is a mix? of only 5 grams bento with 100ml(grams) water. But according to her, after 5~10 min it should disperse and after ~5 hours settled down so clear water on top can be siphoned. Mine didn't go like that:

at T+1 minute:

at T+6 hours:

at T+ 18 hours:

at T+ 24 hours:

should I stop this? It feels like it's going to mold.

[Babs]

Ok so you are adding 5% B onto a surface, small surface area.

Sue had a BUCKET, I didn't read closely but as Benton. additions are usually 1 to 2% by weight, which could mean a very light sprinkling over the surface.

With a mix , your last sample good to go. A Slake of 24hrs not uncommon.

I would put your small amount of dry clay and Bentonite in a jar, shake it up, add it to an   amount of water, more than you need. Give it a good mix or two. Slake overnight. Leave a day, drain off any clear water, spread on your drying board and go from there.

Bentonite is extremely hygroscopic.

 

[Kelly in AK]

That looks exactly like what I would expect bentonite to do. The part touching water swells and doesn’t let water pass further. A thin dusting might settle right away, but any more than that you’ll have a pile of dry material on top of a layer of impervious wet gel. I’m not sure what the scum on top after it all settled is. Could be bentonite with air trapped as a foam.

It should feel greasy, almost soap like, between your fingers.  It’s an amazing unusual clay mineral. 

[Tina01]

13 hours ago, Babs said:

Sue had a BUCKET, I didn't read closely but as Benton. additions are usually 1 to 2% by weight, which could mean a very light sprinkling over the surface.

With a mix , your last sample good to go. A Slake of 24hrs not uncommon.

Thank you! If you watch the video on that page, the nature of the whole process seems different.  it just submerged after a couple of minutes and was crumbling under water to fully disperse (in 5 hours she says). but mine didn't sink until after 18 hours and it was still a clumpy. then it raised to top again. 

The 5 grams in 100ml I used was derived from@glazenerd formula, which originally was 5g to 220g of clay and 75ml of water.

By the last sample if you mean the last two photos (after 24h) I was hoping that it should have dispersed and sunk completely (vs 5 hours). Perhaps the container wasn't large enough as you said or my bento isn't really bento.

 

7 hours ago, Kelly in AK said:

A thin dusting might settle right away, but any more than that you’ll have a pile of dry material on top of a layer of impervious wet gel. I’m not sure what the scum on top after it all settled is.

Hi! : - * Thank you! 

Yes, a thin layer settled as it's visible in the first photo. I also doubt about it, if it submerged totally (at 16 hours) why again some of it rise to the surface? as you're not sure what that "scum" is, and I wasn't either, so I asked that if I should dump those perhaps using a spoon in my previous post. 

Now after about 36 hours it seems a  little of that top layer (about 1/3) has settled and slightly smells molding (but no visible evidences yet).

Again, Thank you both for your help and care. 

 

p.s. As many times mentioned in this thread that bento can absorb water 15x  its weight, 5g could absorb 75g, or 75ml water. However what I see is more than 50ml is still free water.

Edited November 16, 2022 by Tina01

[PeterH]

3 hours ago, Tina01 said:

p.s. As many times mentioned in this thread that bento can absorb water 15x  its weight, 5g could absorb 75g, or 75ml water. However what I see is more than 50ml is still free water.

I really hope it isn't necessary to try it, but I found this test method
TECHNICAL NOTE -BENTONITE SWELL INDEX
https://globalsynthetics.com.au/wp-content/uploads/2016/05/TECHNICAL-NOTE-SWELL-INDEX.pdf
ASTM- D5890 is used to determine the swell index. A 2g sample of dried and finely ground bentonite clay is dispersed into a 100 ml graduated cylinder in 0.1g increments. A minimum of 10 minutes must pass between additions to allow for full hydration and settlement of the clay to the bottom of the cylinder.
These steps are followed until the entire 2g sample has been added to the cylinder. The sample is then covered and protected from disturbances for a period of 16 - 24 hours, at which time the level of the settled and swollen clay is recorded to the nearest 0.5 ml.
...
While the sodium bentonite clay utilized in Bentofix® GCLs typically meets a Swell Index in the range of 24 ml – 36 ml, the targeted minimum value is 24 ml /2 g. This minimum value will generally ensure the specified performance of a GCL product is achieved.

Obviously 24-36 ml/2g = 60-90 ml/5g, and note (presumably active) dispersion of 0.1g increments.

 

PS Should you try this --  and it gives an acceptable result -- maybe your bentonite is just extra difficult to wet. In which case using pre-slaked bentonite could be important helpful when making additions to your clay.

Edited November 16, 2022 by PeterH

[Babs]

I will end my cpntributions to this by saying a LOT of solutions to problems or questions in Ceramics are/ should be prefaced by the phrase " it depends"

Not everything is or can be black or white, right or wrong. 

The slaked bentonite is one way to go.

Wearing a mask and mixing it with the clay prior to wetting another.

Because the chemical equation calls for 100mls of water, hmm 

I would sat It depends! I want a really mixed hydrated clay body so I would  add lots more and give it the time it requires to get there. The moulds could be plasticisers!@

Be careful not to throw out the baby with the bathwater.

Next batch of clay will be different.

Enjoy the process.

 

[Tina01]

On 11/16/2022 at 4:06 PM, PeterH said:

Obviously 24-36 ml/2g = 60-90 ml/5g, and note (presumably active) dispersion of 0.1g increments.

 

PS Should you try this --  and it gives an acceptable result -- maybe your bentonite is just extra difficult to wet. In which case using pre-slaked bentonite could be important helpful when making additions to your clay.

Hi! and thank you for these details! 

Now unfortunately I can't do it with such a precision, (in 0.1 of grams). But for sure I will keep trying! Now about 72 hours most of it has settled and there seems no more activity, and also the top layer seems totally dry (even though the lid was on it the whole time). so I will remove that.

 

11 hours ago, Babs said:

I want a really mixed hydrated clay body so I would  add lots more and give it the time it requires to get there. The moulds could be plasticisers!@

Be careful not to throw out the baby with the bathwater.

Next batch of clay will be different.

Hi! and thank you for your response!

Yes, the next batch will be different hopefully the one I'm looking for! perhaps I should've listened to @Min also and try to make something with ready-made clay, but I have this bad habit of trying to understand everything at once and doing all the work myself, from hunting to glazing. I will continue anyway! 

So again thank you and thanks to all who share their experiences. It's a huge help for me and I highly appreciate it! 

[PeterH]

26 minutes ago, Tina01 said:

Now unfortunately I can't do it with such a precision, (in 0.1 of grams). But for sure I will keep trying

What is (probably) important is that you add the bentonite in very small quantities, preferably sprinkled over a significant area. Then allow a little time before agitation, as you really want the bentonite to drop through the surface into the water of its own accord.

IIRC the way it would be done in a lab is to place all the bentonite in a thin line on a glazed tile. Then cut small lengths off the line as required with a sharp edge (traditionally a razor blade).

[Tina01]

Hi all! 

Some updates... I finally built and cooked my first pot! : ) well... it's a vase I guess. I don't know if it has cooked thoroughly or not, but it turn from slightly greenish gray to pinkish beige. A few small areas had a different , more saturated green hue when I took it out of my kiln. It's hard on surface, not scratches with fingernails but does with sharp metals. Absorbs water but doesn’t disolve or making my finger muddy when rubbing it wet. Still I'm afraid to fill it with water although some smaller thinner testing items I cooked with it are still  holding strong  under water after 20 days.

hunting/making clay is still in progress. as the last formula didn't work (infact it couldn't be tested as it had a horrible smell, something like fetid swamp rotten eggs after 5 days). Most likely because my bentonite keeps molding, no matter how many times I remove the mold layer from the top. So I finally mixed all the different clays I had and still working on dry powders to find a solution. 

[Kelly in AK]

Tina! You just made my day.

[Tina01]

2 hours ago, Kelly in AK said:

Tina! You just made my day.

: ) Thank you sooooo much! kisses! ; )

[PeterH]

On 12/20/2022 at 6:57 AM, Tina01 said:

hunting/making clay is still in progress. as the last formula didn't work (infact it couldn't be tested as it had a horrible smell, something like fetid swamp rotten eggs after 5 days). Most likely because my bentonite keeps molding, no matter how many times I remove the mold layer from the top. So I finally mixed all the different clays I had and still working on dry powders to find a solution. 

You could prevent the mould by adding a biocide. Short lived ones (that require topping up) are hydrogen peroxide and bleach (but bleach may be hard on the hands). A long-lived one is copper carbonate. 

The Best Way to Eliminate Odor from a Stinky Ceramic Slop or Glaze Bucket

- Try to make sure that your waste doesn't get near any aquatic life, especially if you use a long-lived biocide.

- I could understand your "wild" clay going mouldy if it has lots of organics in it, but am surprised that shop-bought bentonite does.