Reclaiming Large Quantities of Clay

[Vik]

Hi there! 

I work at a local Maker Space and we currently recycle three different clay bodies in the studio. Our current setup consists of three separate 32-gallon garbage cans. However, we are facing an issue with the water not draining properly when we dump all the clay scraps from throwing into the cans. This makes it challenging to reclaim the clay in a timely manner. On the other hand, if we remove the water used during the throwing process, we tend to lose a significant amount of fine loose particles, causing the clay bodies to fall apart. Since we share the space with other areas, we have limited space available for the reclaiming process.

Additional information: We do have a pugmill for the reclaiming process. 

[Pres]

I would start by having a smaller bucket (5gal) for throwing  to be tossed into and let set, then drain off the water after a day. If this is too small, use several 5 gal. buckets and drain and empty cycling through the buckets. This process should help  you with the excess water problem, but you may also need to have a large plaster slab to put clay onto to dry it even more. several of these may make it easier to work get to the pugging stage. Old tech, but works. One last thought is that I have used large hanging bags like pillow cases to put slop into, allowing them to dry/drain then invert them to pug the clay.

 

best,

Pres

[glazenerd]

Vik:

One of those cases where the tricks of the wild clay collectors comes in handy. Pour the whole bucket through a pillow case; tie a loose knot on the end, and hang up outside and let it firm up. With current outside temp, check it morning and evening until it “feels” right. Then you can pug it up.

Tom

[Callie Beller Diesel]

I agree with Pres: the biggest thing you can do to reclaim clay in a timely manner is to have a smaller reclaim bucket that obliges you to do it more often.

Also, if space is a problem, you can build stacking frames to do reclaim on, similar to the principle Tom describes. This article (there’s a paywall, but you can access 3 free articles a month) describes how to build a gravity filter press. All you need are some 2x4’s, hardware cloth/chicken wire and a thrift store bedsheet. You can use this method to build stacking frames that have a smaller footprint, and even have separate trays for the different clay types.

I do my reclaim on a similar setup, and I find as long as your slurry isn’t super fluid, you don’t need the plastic to catch the runoff. I aim for a pudding consistency. 

[Kelly in AK]

I use something similar to dewater clay. There’s no moving these when they’re full though. 

[Min]

Another thing you could do is see if your claybodies are available dry. If they are then after slurry mixing the slops with the reconstituted scrap pug it together with some dry clay to get the right consistency. Even sprinkling the slurry with the dry body would help, it also helps return the body to closer to original state if it's missing fines.

[neilestrick]

The vast majority of places I see using dry clay to recycle are not actually properly set up to deal with the dust created from using dry clay. If you don't have proper ventilation then don't do it.

[Piedmont Pottery]

In addition to using smaller buckets, adding a bit of Epsom salts to flocculate the clay will make the fine particles settle much more quickly, allowing you to remove the clear water above the clay layer.

[Callie Beller Diesel]

@Piedmont Potterydo you find that the epsom salts affect how the reclaim throws afterwards? Or is it not enough material to affect the batch?

[Vik]

Hey Everyone! I want to thank you all for your advice! My maker space will try a lot of these out to see which will work best for us. I'll be sure to keep this thread updated with our progress. @Piedmont Pottery I'm also curious if you find that adding the epson salt affects how the reclaim pottery throws afterwards in addition to firing and glazing. 

[Piedmont Pottery]

On 7/16/2023 at 1:19 PM, Callie Beller Diesel said:

@Piedmont Potterydo you find that the epsom salts affect how the reclaim throws afterwards? Or is it not enough material to affect the batch?

If anything, I find my recycled clay may throw a bit better than new clay.  While I suspect that there may not be enough epsom salts to affect the clay chemistry significantly, in theory, flocculating the clay should improve plasticity.  I've seen no changes in glazing between new and reprocessed clay.  I have not done any kind of systematic test to look at the impact of MgSO4 on clay properties, and I don't measure the amount I add per bucket.  I just pour in a bit of saturated epsom salts solution to the bucket.

[glazenerd]

Epson salts are basically magnesium sulfate. 20% +/- magnesium; which is the clay world is a body flux. The sulfates will burn out. Given the amounts used; nearly zero effect. At most, the magnesium will change a high white body to an off white body; and that would require larger additions than what is being discussed. 

Tom

[grackle]

I do use 5 gallon buckets and they work well, however I suspect I may be creating some problems for myself in that I do not always make sure i put just one type of clay in each bucket.  I typically use 4 different kinds of clay, 3 are cone 6 and one is a cone 5.5.  I have a white stone ware and a white porcelain, and I know that i have sometimes mixed them in a recycle bucket.  I can see the bits of porcelain in the cut clay after wedging.  Is this a bad idea?

I also have a red stoneware clay, and the 5.5 is a very dark, somewhat groggy clay that i have a love hate relationship with.  Glazes are beautiful on this dark clay, but tend to bubble a bit, so I thought perhaps if I mixed some dark scraps into the red clay bucket, it would tone it down a bit.  Does seem to help, but now I am reading about things like different shrinkage rates, etc.  And the red is cone 6 and the dark (fires almost black) is 5.5.

Any thoughts would be much appreciated!

[Hulk]

Testing tells the tale!

I've tried mixing clays in reclaim - just once so far - was not pleased with the results!
Two of the three clays in the mix had some problems I'd hoped would be ameliorated by the third clay.
The "good" clay was just over half, by volume, and the most problematic clay less than fifth; still, the "bad" showed through, big time.

I've just bagged some buff reclaim this week, where I tossed in a small amount of speckled buff with the other buff.
Both clays "behave" - hence I'd like to expect that the result will be great.
Still, I plan to include just a few pieces and some test tiles, test test test! ...then go from there.

[grackle]

Thanks, Hulk.  I am beginning to suspect you are right.  Fortunately, since my production is small, I can probably just use the Mixed reclaim for small handbuilt projects, and just start over with keeping the various clays separate.

[Kelly in AK]

At school I occasionally end up with a few different clay bodies for the students. Sometimes other schools will give away clay that’s too stiff to use, since I have a pug mill I always get as much as I can.

After fifteen years doing it, the biggest problem remains the “other stuff” that sneaks into the reclaim bucket. The pugger mixes everything into a homogeneous body and it all starts as cone 5/6 clay.

There was a year I got some porcelain and that required a few trips through the machine to get it mixed in well (didn’t have a pugger-mixer at the time, just a simple pugmill).

Edited August 15, 2023 by Kelly in AK

[Pres]

I have always tried to limit my number of clays so that I don't have to deal with mixed bodies. One clay is dark  another white and that makes it easier. However sometimes trimmings do mix when I get lazy. However, both clays fire the same, and have the same characteristics but different colors. Occasionally you will see a dark streak or light one running in the body as I only hand wedge reclaim.

When teaching, I had the Walker for pugging, but we never had more than one clay at a time in the studio . . . good old SC 200, or SC 112. They played well together, but I only bought one or the other each year.

 

best,

Pres

[grackle]

in college, when i was learning ceramics, they had an old big cement mixer out back, and all the scraps and clay water went in there.  we used two clays, a white and a red from Armadillo Clay, both cone 6.  The instructor would add dry clay when we ran the mixer, and  I do not remember a pug mill (i think we just hand wedged).  i remember looking into the mixer one day, and it was full of mosquito larvae--this is Texas after all!

So, okay, since I am a bit lazy and retired, just doing this for fun and family mostly, i now think I will try to keep things separate, but not get obsessive about it!!

[grackle]

also quite taken with the idea of small streaks of light and dark.

[Callie Beller Diesel]

If you’re going to mix clay bodies in the reclaim, it’s best to make sure it’s a completely homogeneous mix if you want minimal fuss. Slurry mixing the reclaim or running it through a pugmill until the streaks are gone are both ways of doing that. As long as it’s a homogeneous mix, it’ll be a brand new clay body with properties of all the components. If they all fire at roughly the same temperature, you probably won’t have to mess with the firing cycle, but you’d have to keep an eye on the level of black clay in the mix if it bloats above 5.5. If you don’t want to do a bunch of testing, you could make planters, stepping stones, sculptures and other things that porosity probably doesn’t matter for. 

If you want to have a marbleized look, it may well be possible to combine some or all of your clay bodies, but you’d have to make a few samples and stress test them to be sure. If you let us know what brand, we can help look up specs or see if someone here has tried with those specific ones. 

Whether diluting the black clay in red fixes blistering/pinholing problems related to off-gassing will probably depend on the proportion of red to black clay. Do you happen to have an estimate of what proportion of each clay went into your test?

[Kelly in AK]

Mosquito larvae enhanced the plasticity.

(Just kidding. Don’t try it.)

[oldlady]

not having an education at a college or university, i just think logically about reclaim.  i never wet anything until the day before i pug everything.  learned i cannot wet a partially dried piece so i do not even try.

using only one clay makes it simpler.  when i used a red as well as a white, i marked one clay bag RED.  since i work mostly with slabs, it is very easy to have an open clay bag sitting on the floor next to the slab roller.  as pieces are cut from the large slabs i make, the trimmings drop into the bag.  the pieces i make take some time, and i proceed with making flat things until i have filled the shelves in the studio.  the glazing takes time as well and so the trimmings are totallydry before i am ready to pug.

by this time there are 4 or 5 bags or buckets waiting for the pugmill.  everything is transferred to buckets, outside the studio while wearing a respirator.   the buckets are moved to the pugmill and distilled water is added to each bucket to an inch or so above the level of clay scraps.  the dry clay scraps absorb the water overnight

 

the next morning, my Bailey does the mixing and air removal and i do it twice just to be sure the blend is thourouglhly mixed.  there are usually some damp pieces left from recent throwing so they go in as well.   what results is a great throwing body that i enjoy using to make empty bowls for the annual winchester va dinner.

you may not buy as much clay as i do so do not have bags of trimmings.  you may not have a pugmill or access to one.  but you do have access to some kind of container of scraps and some tabletop space for piling up the trimmings as they occur.  they dry pretty well overnight and can be put in a bucket waiting for you to wet and wedge into pliable clay.

Edited September 9, 2023 by oldlady
correct