Short clay

[Claymade 1]

Taking over a college class for a friend and found that the clay body is very "short" . Does well with pinching and coiling but is cracking a lot with a slab roller. Any quick fix ideas? I can't age it for 3 months. Thanks!

 

 

[hitchmss 264]

Access to a pug mill? Is this clay that has been made in the studio, or commercially prepared clay? Usually commercially prepared clays, if they are for throwing, or general production methods, then it is very plastic. If its a sculpture body it may not be very plastic.

If you dont have access to a pug mill, then wedging on a table that you spritz with water will help work moisture into the clay, which will improve its plasticity. If you do have access to a pug mill/mixer, then additions of 1-3% of bentonite/macaloid will help. If it already has a plasticizer in it, you may not want to add much more....can lead to less than desirable working/drying characteristics.

[neilestrick 3,566]

There can be different reasons for a clay being short. How is the clay body processed? Has it gone through a de-airing pug mill?

[Claymade 1]

Thank-you both for your quick replies! This was commercially prepared clay that has been repugged many times, but not in a de-airing pugmill.  A potter friend in her 60th decade of clay making said that in the old days a bar of Ivory soap was slaked down in water and then added to the clay to quickly increase plasticity.  What do you think? We will continue to wedge. I am just very spoiled by our de-airing pugmill at my other school!

[Benzine 1,066]

If the clay is reclaimed, from throwing, the clay could be short, if the watery slurry from the throwing, is not included with the drier bits.  There are a lot of finer particles in that water, which help with the clay's plasticity. 

Ivory soap, that's a new one!

I've heard of vinegar being added to clay, to help with plasticity.  I'm not sure what the soap would do, other than make it smell better.  Though, you could be on to something.  A clay that washes your hands, while you work!

I joked with my instructor in college, that they should make a clay, with a lotion base, so your hands aren't dried out, when working.

Edited February 14, 2019 by Benzine
Added additional information.

[Rae Reich 432]

Wedge in ball clay and water.

[Denice 659]

When I have a clay that seems to dry,  I put it in a bag with a little water.   The amount of water depends on how much clay you have,  you put the bag in a 5 gal bucket of water.   Over night the water pressure pushes the moisture throughout the clay.  If it is really hard will take 2 days.     Denice

[hitchmss 264]

If the recycled clay has been run through the pug mill, just once, I might suggest running it through again. A deairing pugmill will input more force onto the clay as its being pugged, which will help compress the clay and imrpove plasticity, but just being forced through the nozzle of the mill may help; you may want to try adding a little more moisture than you would normally like your clay at, which will improve the plasticity, and then just let your pugged logs sit out for a couple hours to get to the dryness you want.

Ive never heard of the ivory soap trick; not sure how Ivory makes their soap, but there may be some materials in there which actually do improve plasticity (on a chemical basis) and not just having soapy/slippery clay where the soap is acting as a filler and not really binding the particles together. I could see this trick going poorly if the amount of soap added to the clay was so much, that when fired, your pot would be much weaker, because all that filler was burnt off.  Same deal goes for bentonites; very small organic particles which absorb high amounts of water, but also have a high LOI; 1-3% works well for most clay bodies, but if you were near 7-10% you would notice adverse effects.

The vinegar, or other flocculants work on a chemical/molecular level to bring the particles into a tighter matrix, providing plasticity without sacrificing fired strength.

[Min 2,471]

If it's all made of scraps that have been used and reused many times then try adding some new unused clay to the pugger along with the tired old clay.  Run the clay through two or three times to get it all blended together and give it a try. If the work is for functional pots check the absorption hasn't increased too much from original unused clay.

[Claymade 1]

Thanks again to all. Forget the Ivory soap- try the vinegar, wheel water, repugging, new clay (I like this!) I am very grateful for this forum!

[liambesaw 1,846]

I believe @glazenerdhas a recommendation of adding a mixture of ball clay, feldspar and silica to reclaim to give it back some legs too.  I have added om4 to reclaim before and it worked too.

[Babs 940]

If its ok to pinch and coil are you trying to get it too thin too fast in roller. Also it may just be too dry for slab roller.. just thoughts because I find tbis can happen rolling a body which at right dampness to coil and handbuild needs to be a little damper for rolling directly on my worktop.

 

 

Edited February 15, 2019 by Babs

[glazenerd 1,501]

Fix It mix for stoneware is: 80% OM4, 10% silica, 10% feldspar. 

Add 1/2 to 1 cup per gallon of reclaim. ( sounds like you need at least a cup).

[Marcia Selsor 1,816]

there used to be an additive called "plasticizer" .  maybe it is still around. Vee-gum is also

a plasticizer.

 

Marcia

[oldlady 2,425]

a very quick way to make clay more pliable is to form a thick sausage about the thickness of your arm, wrap it in a very thick, very wet towel and smack it with a stick.  not a yardstick stick, a club like stick.   when you unroll and wedge it, the water helps and the smacking makes it more thixotropic.  

[Kristina Vatne 2]

On 2/14/2019 at 6:02 PM, glazenerd said:

Fix It mix for stoneware is: 80% OM4, 10% silica, 10% feldspar. 

Add 1/2 to 1 cup per gallon of reclaim. ( sounds like you need at least a cup).

Would this work for cone 6 midrange stoneware? Or is it strictly for high fire?

[glazenerd 1,501]

48 minutes ago, Kristina Vatne said:

Would this work for cone 6 midrange stoneware? Or is it strictly for high fire?

Cone 6 stoneware 76% OM4, 14% feldspar, 10% silica. ( This is a plasticity fix only.)

[Kristina Vatne 2]

23 hours ago, glazenerd said:

Cone 6 stoneware 76% OM4, 14% feldspar, 10% silica. ( This is a plasticity fix only.)

Thank you very much!