Reclaim Clay — Posts — The Studio Manager

Recycling and reclaiming clay is a constant job in any ceramic studio. If you work in a large or shared studio, it’s probably best to get a pugmill or mixer. But if you are working alone or in a small studio, you can easily stay on top of your reclaim following this method. It’s especially important if you create a lot of trimmings from wheelthrowing.

Here’s how to do it.

Step 1

Dried clay scraps ready to be reclaimed. This clay is in our favorite Red Gorilla Tub.

Gather all your dried scrap in a bucket. For this method, all the clay must be completely dry. This is is easy if it is thin trimmings, but you may need to break up larger chunks and give them time to dry. When working with dry clay, take care to avoid breathing clay dust—a respirator is best.

In the picture here, it’s about 6 lbs of dried scrap, which will turn in to about 10 lbs of workable clay.

Step 2

Add water. Add enough water to reach about 80 percent of the height of your scrap. Don’t worry if you add too little or too much.

Step 3

The dried-out clay scraps will quickly slake down in the water.

Let the clay slake down in the water. If you have just thin trimming scraps, this could be a matter of minutes up to about a half hour. If you have bigger chunks, it could take a few hours for everything to completely hydrate.

During this stage, you can add more water if needed.

Slaked-down clay. It will feel like a very thick slip.

After the clay has completely hydrated, it’s ready for the next step. It should look like this, or it may have fully submerged under the water.

If you stick your hand into the clay, you shouldn’t feel any hard lumps or chunks.

Step 4

Clay spread out to dry on a plaster wedging table — Clay spread out to dry.

Spread the clay on an absorbent surface such as a plaster wedging table or plaster bat. Keep the clay about an inch or two thick. You can add finger holes to increase the surface area touched by air, but the main source of drying will be the absorbent plaster.

Step 5

The clay has dried on one side and can be peeled up and flipped.

After drying for a few hours, the clay will still be quite wet. But if you can peel it up and find a drier “skin” on the bottom, it’s ready to be flipped. This will help equalize the drying time.

Step 6

Depending on the conditions in your studio and the ambient humidity, they clay may dry quickly. If you are out of time for the day, just cover it with plastic to slow the drying.

For this demo, the clay was covered after being flipped once, but you could choose to cover the clay at any point and walk away. Or your studio might be dry enough that it can all be done during your workday.

The clay after sitting under plastic overnight. It is ready to be wedged.

Step 7

Clay that can be peel off the plaster surface is ready to wedge.

The final step is wedging the clay. If you can peel up the clay and it is somewhat dry, it’s ready to wedge.

The clay is easiest to wedge when it is soft, but not so soft that it’s sticky.

Step 8

The wedged clay, ready to be made into something new.

The clay can be used right away. Or even better, bag and store the clay for a few days and then wedge again. This way you can be sure that all the clay is completely mixed.

What reclaim technique works for you? Let us know in the comments.

Updated and revised, September 9, 2023

A dirty, stinky throwing slop trash can in need of some cleaning and copper carbonate, to eliminate odors.

Stinky slop and glaze buckets can be a problem in any ceramic studio. The smells range from a swampy, pond-mud smell to a very strong sulfurous odor. All are caused by some kind of organic matter in your clay or glaze.

In addition, some glaze materials such as bone ash or CMC are organic materials and will start to smell over time, especially if the bucket is not stirred regularly.

To deal with smelly buckets, the best practices are to:

Keep organic materials like brush bristles, paper, etc out of your buckets and jars
Stir and mix your materials more frequently
Cycle materials more frequently
Clean your buckets with soap and water, and sterilize them with bleach

Adding bleach? In some studios, bleach is added to slop buckets or clean up buckets and mixed with the clay slop. This is an ok thing to do, but has it’s drawbacks. Usually, the bleach will just mask whatever the problem is for a few days or weeks, and then the smell will return. And I personally don’t like to add bleach to buckets where the material is being recycled such as clay slop buckets. And if you add too much bleach, the slop water can be rough on your hands.

The following article covers some ideas for eliminating odors from glaze buckets, underglaze jars, and slop buckets. Discussed is a somewhat extreme method of adding copper carbonate. In general, I would use this as a last resort after you have tried to cycle material, or clean outed and sterilized the problematic bucket. A little bit of copper can get rid of smells, because of the antimicrobial properties of the element, but using it does have some drawbacks as well.

This practice of adding a small amount of copper carbonate comes from a tip I read many years ago I read in Ceramics Monthly. (I haven’t been able to find the link) The tip from the potter was adding a trace amount of copper carbonate to glaze buckets. My memory is just a gram or two. It wasn’t enough to change the color of the glaze (even in a white glaze), but it was enough to prevent mold growth. If you have a glaze that regularly smells, try adding an extremely small amount of copper carbonate to any glaze, and see if that fixes the problem. The tutorial below also covers adding copper carbonate to slop buckets, in addition to some strategies to deal with smell glaze and underglaze jars.

Shop Copper Carbonate at Amazon

How To Eliminate Odor From Glaze Buckets
How To Eliminate Odor from Underglaze Jars
Maintaining and Dealing with Odor in Slop Buckets and Reclaim Clay

How To Eliminate Odor From Glaze Buckets

Stinky glaze buckets happen from time to time. Usually, this is caused by some sort of organic matter. It could also be caused by organic glaze materials such as bone ash or CMC gum. For bone ash glazes, try stirring the glaze more often, or proceed with the copper carbonate fix as detailed below. For glazes with CMC gum, try replacing that with bentonite, which is a very fine, inorganic clay that can help glazes stay in suspension.

Before adding copper carbonate to a stinky bucket, screen the glaze first to make sure you’ve removed any brush bristles, bisque chunks, or other foreign matter. Sometimes, just stirring the glaze more often may eliminate the issue, so try that first!

Method:

Add 1 gram of copper carbonate per 5 gallons of glaze, stir, and wait 24 hours.

That’s it!

Just a bit of copper should take care of the problem, and in such a small amount, it shouldn’t change the color of the glaze. I even did this once with 5 gallon bucket of white glaze. A little risky, but it worked without changing the glaze color.

If you are nervous about adding copper carb, or if your studio scale is not very accurate, try measuring the smallest amount you can, such as 2 or 5 or 10 grams, and then physically dividing it up to get down to something like .5 grams or 1 grams, and add that small amount to your glaze. If the smell isn’t gone in 24 hours, repeat the process.

If the copper carbonate doesn’t solve your problem, don’t keep adding it past 2 or 3 grams. Eventually, you will add enough to alter the color of the glaze. If the problem persists, you may have to discard the glaze and start over with a fresh batch.

How to Eliminate Odor from Underglaze Jars

Underglaze jars can get really stinky. Some in particular, such as the various reds from the Amaco Velvet Underglaze line, seem prone to getting stinky.

To prevent odors with underglazes:
> Remove any cardboard liner from the caps
> Stir to mix. Don’t shake all the underglaze against these cardboard liners
> Try to prevent brush bristles from dropping in
> Keep any other organic matter out of the jar

But if your underglaze gets stinky? There may not be much you can do. It’s such a small volume, and our best remedy, copper carbonate, is a colorant. Still, you can try adding a very small amount of copper, approximately 1 gram or less. Stir into your underglaze, cap it up, and wait 24 hours. Check and repeat if necessary. Caution: you will change the color of your underglaze if you add copper to them! I’ve done this a few times with the extremely-prone-to-stinkiness Bright Red Velvet Underglaze. The copper mutes the red a bit, but it’s actually a lovely result that is still red.

But the conclusion is, there may not be much you can do for a stinky underglaze except to tolerate it and/or discard and buy a new jar.

Maintaining and Dealing With Odor in Slop Clay Bucket

A slop bucket is a great way to reduce the amount of clay going into your sink and can also be used for initial cleaning of splash pans and throwing buckets. If there was room, I’d have a series of three of these for cleanup. But in the studio I manage, there is just one 40 gallon trash can with a mesh lid. It’s used to collect all the throwing slop.

Ideally, this trash can gets completely emptied about once a month and the heavier slop is saved and mixed with reclaim clay. But while the slop is building up, the bucket can get pretty stinky. And if you recycle stinky slop, then you have stinky reclaim clay (although the process of mixing does seem to help alleviate some problems with smell.)

The first step I would take with a stinky slop bucket would be to completely empty it and clean with soap. Then, sterilize the bucket or trash can with bleach and let it dry completely. Usually this will eliminate your stinky slop bucket problem for at least a few months up to 6 months. Slop buckets will always get smelly at some point so just plan to fully clean and sterilize it on a regular schedule.

A more extreme solution is adding a small but regular dose of copper carbonate to your slop bucket. Caution: adding copper carbonate to reclaim clay may result in small green spots showing up through white or clear glazes as you are adding copper to your clay! Use this method at your own risk.

The tutorial below covers maintaining a slop bucket with copper. As mentioned, try cycling your materials more regularly, keep organic material out of your bucket, and give your bucket a deep clean before trying this method!:

Step 1: Remove water, add copper carb, and stir

Ideally, the slop bucket is a settling tank so that heavier clay particles will separate and fall to the bottom. Pictured here is a 40 gallon trash can. As the can fills to the top and settles, pull off the top 10 gallons of water. This watery slip goes down the sink in my studio, but you could choose to let it settle and then decant.

After taking off the top 10 gallons, add about a half a spoonful of copper carbonate. This is about 2-3 grams of copper carbonate.

After adding the copper carbonate, stir or mix the whole slop bucket with a drill. It helps to disperse the copper.

Add about 1/2 spoonful of copper carbonate per approximately 20-30 gallons of slop. — Add about 2 to 3 grams (about 1/2 spoonful) of copper carbonate per approximately 20-30 gallons of slop.

Copper carbonate on the surface, ready to be mixed into the slop.

Step 2: Clean the Lid

Not exactly necessary, but a regular lid cleaning makes it easier to maintain and inspires respect from your fellow studio mates.

It’s a bit hard to see in the picture, but I am are using my favorite pro-grade cleanup sponges.

For the lid on our bucket has a DIY screen made by cutting a hole in the trash can lid and attaching rubberized mesh with nuts and washers. The mesh helps to keep tools, sponges, and large chunks of clay out of the slop bucket.

Step 3: Repeat as Necessary

Our bucket with a clean lid and a bit of copper to prevent any stinky odors.

As stated above, it takes us approximately 1 month to end up with about 15 gallons of heavy slip but usually every week or more often, I remove the top layer of watery slip from the bucket. Every time water is removed, I add copper to the bucket.

Once there is 15 gallons or so of heavier slop at the bottom of the bucket, I remove it and put it in 5 gallon “settling tanks,” This watery slop is then poured over dried out scraps or added to the pugmill as needed. It’s the best way I can think of to capture all the fine particles left over from the throwing process. I’ve also found that as this slop with copper moves through the reclaim process, it combines with other clay and helps keep that reclaim from getting stinky too.

Occasionally, I do notice a little green copper speck popping into a white glaze from the reclaim clay, so if you want to be extra careful, use the least amount of copper necessary, or mix it into a watery slurry before adding to your slop bucket.

Summary

This post has covered a variety of ways to deal with smelly glaze, underglaze, and slop buckets. Also detailed is how to use copper carbonate to eliminate odor in glaze buckets, underglaze jars, and slop buckets. It’s an effective and affordable way to manage the inevitable odors that arise in a ceramic studio.

Do you have any other techniques for maintaining odor-free slop and glaze buckets? Let us know in the comments.

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