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Inconsistent Clay?


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I have a question about clays.  I've found that the Standard Ceramic Clays I am buying are very inconsistent in hardness. Is this true of all clays?  Just when I think I've found a clay that I can throw easily, the next box has a totally different feel.  It's not a problem for handbuilding, but really limits my throwing size.  I work with cone 6, and there's only one ceramic supply place nearish-by, (hour and a quarter away on a good day), and it only carries Standard clay.  I really liked the Little Loafers I bought online and would be happy to do that again, if it will feel the same each time.   What's your experience on this issue?  Are all clays inconsistent from batch to batch or is there a difference between manufacturers?

 

Thanks!

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It could be inconsistent to it could be the age and dryness. You can ask how old it is when you buy it. For commercial clay I buy, I always throw it on the concrete floor at least once on all 6 sides.This softens it up usually unless it has dried out beyond this point. Some of my clay can be 9 months old, depending on what I have been doing.

 

Marcia.

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and there's only one ceramic supply place nearish-by, (hour and a quarter away on a good day), and it only carries Standard clay.

 

If its the only clay they carry, and the only one within a 100 mile radius: then I would have to assume it is not old stock. I do not use Little Loafers, but I see posts about it all the time. The most common is how "smooth and creamy" it is. "smooth and creamy" means high % of ball clay (extra fine). "smooth and creamy" also means smaller amounts of fire clay, and more than likely by the color: Imco 400. Again by the color: a kaolinitic ball clay at that.

 

All of which leads me to think they are being inconsistent in the amount of water added to batches. OR, they need to up the percentage of water they are adding per batch. Extra fine ball clay + Imco 400 means it will absorb up to 10-15% more water than is added. So it will come out of mixer nice and smooth: but within 1-2 months it will begin to get firm; after 3-4 it will be firmer yet.

 

There are things you can do to rehydrate it: will let others address those fixes.

 

 

Highwater clay not only had contaminants in them, but is so snotty wet

Roll one entire sleeve out on your slab roller: thin as possible 1/4" or so.  Pending the room temp and humidity: let it sit from 1-4 hours open. Then wedge it on a plaster board to get it into your preferred moisture range.OR.. just let it sit in the bag for a few months: let the clay age.

 

Nerd

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It's all about how much water they add during mixing. If the production manager isn't checking on the production team, then it will often come out too hard or too soft. The guys mixing the clay probably aren't potters, so they don't necessarily know exactly how it should feel. Plus it doesn't take much water to make a batch too wet. 1 gallon can have a noticeable effect on an 18000 pound batch. This time of year makes mixing difficult, too, because humidity levels are constantly changing, so sometimes the clay dries out a bit during mixing and sometimes it doesn't. Moisture levels in the raw materials can also fluctuate and affect the batch. It's an inexact process. That said, I called Standard and complained just a couple of weeks ago because I had several batches that were too wet to use. Give them a call and let them know you're unhappy. It's the only way they'll know there's a problem.

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Guest JBaymore

 

 

Highwater clay not only had contaminants in them, but is so snotty wet

Roll one entire sleeve out on your slab roller: thin as possible 1/4" or so.  Pending the room temp and humidity: let it sit from 1-4 hours open. Then wedge it on a plaster board to get it into your preferred moisture range.OR.. just let it sit in the bag for a few months: let the clay age.

 

Nerd

 

 

The poor potter's filter press.  ;)

 

best,

 

...........john

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Reading your posts I can see why my kneading isn't softening the clay - it needs more moisture.  I have had these last couple boxes of clay for a few months, so maybe it's just been sitting around too long.  I tried dropping a bag yesterday as Marcia suggested -  well actually I dropped it many times on all its sides, and it made no difference.  It was kind of fun tho.  

 

I might be better off ordering clay online as I need it instead of buying a lot at one time.  And hope it's fresh.  Or rather I should order by phone and ask if it's fresh.  How fresh  is fresh?  What age clay do I want?

 

If I slice the clay up to stack and slam, and spray some water as I go  would it help or just make a big slimy mess?  

 

Glazenerd, I'm all about wanting smooth and creamy clay.  I've been trying different clays (from Standard Ceramic that is)  but none offer much info about their composition, and even if they did, it wouldn't help me much since I know so little about what I should be looking for.    Is a high % of ball clay a negative?  I know it's a huge topic and I've read a little about it but don't know what the relationships between the different components should be for different applications.  I guess my biggest concern right now would be glaze fit.

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If your clay has gotten to stiff there is a easy fix.  Put a half cup of water in the bag, if it is really hard you may have to poke a few holes.  Immerse it totally in a five gal bucket of water and let it set for a few days and then check it and see if it is soft enough for you.  I would much rather get clay that is to hard than soft, messing with sloppy clay on plaster slabs is a lot more work.   Denice

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I can tell by running a wiretool thru the clay if it can be thrown and what can be made.

 

First I try wedging...if it is too dry to wedge, you can't throw it. Then, I roll the unit of clay into a cone, and drag a wire tool thru it. If I have to hold it in order for the wire tool to exit the clay, its too dry and then I thin slice the clay, adding water between each slice, wedge, stand on its end, and drag the wire tool back thru. When the wire tool passes thru the clay without being held...it's ready to throw...after wedging again.

 

This method pretty much applies with all clays even though I use a lot of red stoneware!!!

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If I slice the clay up to stack and slam, and spray some water as I go  would it help or just make a big slimy mess?  

 

 

Use a small hand sprayer and it'll be fine, just spray the surfaces that are going back together after slicing.

 

If it does get too wet just leave it to dry out a bit.

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Irene

 

 

How do you determine the level of ball clay the recipe had to begin with?    The Cream Test

 

When you throw the original clay: how much cream comes up and on your hands?

 

Coats just the inside of your palms and oozes through your fingers over time.... lower levels.

Coats your palms, and oozes; have to clean a few time while throwing.... mid levels

Oozes quickly and constantly cleaning off hands....... high levels.

 

In cone 6 firings: a high amount of ball clay- cream also indicates that it will have a high vitrification rate if fired correctly. Lots of cream  = lots of fine particles, which = better density packing, which = vitrification.

 

Nerd

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Irene

 

 

How do you determine the level of ball clay the recipe had to begin with?    The Cream Test

 

When you throw the original clay: how much cream comes up and on your hands?

 

Coats just the inside of your palms and oozes through your fingers over time.... lower levels.

Coats your palms, and oozes; have to clean a few time while throwing.... mid levels

Oozes quickly and constantly cleaning off hands....... high levels.

 

In cone 6 firings: a high amount of ball clay- cream also indicates that it will have a high vitrification rate if fired correctly. Lots of cream  = lots of fine particles, which = better density packing, which = vitrification.

 

Nerd

 

Ah, interesting info Nerd, thanks for that.  I'm going to post it somewhere in my workshop for reference,  (also, I think I like your cream test better than Mark C's. :rolleyes:

 

I'll have to pay more attention next time I throw,  tho truthfully I suspect the amount of slush I get on my hands at this point is more a function of the way I throw than what's in the clay.  Or maybe not - I've been using Standard 181 lately, any experience with that?   

 

But back to the cream test, does it then follow that porcelain has a lot of ball clay in it?  

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You'll spend as much on shipping as you will on clay if you order one box at a time online.

 

Which is why I've only ordered clay online once.  I still might end up doing it again, but for now I'm going to make the pilgrimage to the place in Lodi next week.  It's the second Saturday of the month and they have a lot of stuff on sale then, so I'll get some clay and a couple other things I need while I'm there.

 

And ask for their youngest clay.  It just seems wrong somehow......

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But back to the cream test, does it then follow that porcelain has a lot of ball clay in it?

Yes, it applies to porcelain as well. Although there will be some variances because some porcelain bodies have ball clay, others do not. Even those that do not have ball clays will still cream up because of macaloid or hectorite additions.

 

Nerd

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But back to the cream test, does it then follow that porcelain has a lot of ball clay in it?

Yes, it applies to porcelain as well. Although there will be some variances because some porcelain bodies have ball clay, others do not. Even those that do not have ball clays will still cream up because of macaloid or hectorite additions.

 

Nerd

 

 

I've never heard of those.  I'm going to go read up on different types of clay.  Thanks for the info Nerd!

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  • 4 weeks later...

We slam every pug on 4 sides as it does work well for porcelain  before working with it.

I also oder my clay made in winter when its not so hot and dry out in LA where its made. winter clay is more uniform I feel.

Sorry you did not like the cream test-its not an exact science.Everyone is different on who much cream they like in coffee.

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