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Sometimes thrown pottery gets neglected or forgotten. Life gets busy and you come back a week later to an unintentionally bone dry pot. This has happened to me too many times. So, I decided to do some practical research and find out what’s the best way to rehydrate bone dry clay. And this is what happened…
I tried 4 ways to rehydrate bone dry clay pots to revive them. The two methods that worked were the slower methods that used a damp atmosphere. By contrast, the two methods that didn’t work well involved immersing the clay in water. Whilst quicker in theory, they damaged the pottery.
This article is not about recycling clay. Instead, it is about trying to rehydrate bone dry clay so that you can trim it, bisque it, and glaze it. Perhaps you like the piece you have made and you don’t want to destroy it in the process of recycling. If that is the case, then read on…
I will go through each method I tried and give you an overview of what worked and what did not.
Method 1:
The Bag and Towel Way to Rehydrate Bone Dry Clay
What You Need:
- A couple of plastic bags
- Some newspaper
- An old towel (or two)
- Some masking tape/packing tape
Method 1 for Rehydrating Bone Dry Clay – The Steps
- Place one of your plastic bags on a flat surface.
- Put some folded newspaper on the bag and position your bone dry pottery on the paper.
- You are going to be making a plastic tent over the pottery. So, it’s a good idea to put something on the paper that will keep the plastic off the clay. I used a PVA glue bottle!
- Wet some old towels or cleaning rags. Ring them out so they are damp but not sodden. If the towels are very wet, they may create puddles of water on the plastic. If your pottery is sitting in a pool of water overnight it will turn to mush.
Place the damp towels in a circle around the cluster of pots. Try to avoid the wet towels touching the newspaper. Again, if the towel is touching the newspaper the paper will soak up all the water and get soggy. And the base of your pots will disintegrate.
- Cover the arrangement with a sheet of plastic and seal the edges. I used packing tape. I also pinned one edge down with some weights (I used some spare G-clamps I had lying around).
- You can use this edge to look under the plastic now and then and see how the pottery is doing.
The idea is that your clay will absorb moisture from the humid environment and with time will become workable again. I had estimated that it would take a couple of days for the clay to revive. In fact, it took a week. And I had to re-wet the towels every other day.
Nevertheless, after a week the clay was no longer dry. It was leather hard, and ready to be trimmed. The surface of the clay was good and hadn’t been compromised by being rehydrated.
Verdict:
This method took longer than I anticipated. However, it is an effective way to rehydrate bone dry clay using everyday household materials.
Advantages of This Method of Rehydrating Bone Dry Clay
- You don’t need any particular materials. It is possible to find everything you need in your kitchen or studio.
Disadvantages
- It can take up quite a bit of space if you have a few pieces that you want to rehydrate.
- Your pottery is only covered by a plastic bag. They are vulnerable if you drop something on them.
Method 2:
Using A Damp Box to Rehydrate Bone Dry Clay
A damp box is basically any environment that traps moisture and creates a humid atmosphere to keep clay workable. It can keep clay in a workable state indefinitely.
Some professional potters and schools will have damp cupboards to store lots of pottery in.
However, a damp box does not need to be complicated. Some potters simply put their pottery under an upturned bucket with a damp sponge underneath the bucket too.
I sit somewhere in between these two extremes. I have some boxes specifically made to work as a damp box. They are simple to make and a very effective way to rehydrate bone dry clay.
What You Need:
- A damp box.
If you don’t have a damp box, they are easy to make. You can follow my step-by-step guide to making a damp box here. The article has a video and a FREE downloadable checklist to follow.
Here is a short overview of the process of making a damp box for clay. For a full step-by-step video, check out my YouTube channel.
Method 2 for Rehydrating Bone Dry Clay – The Steps
The basic steps of building a damp box are:
- Pour a 1-2 inch layer of plaster into the box.
- Let the plaster set.
- Press and flip the plaster out of the box and clean off all the loose flecks of plaster.
- Reposition the plaster slab in the plastic box.
- Moisten the plaster and put your pottery on the plaster.
- Close the lid of the box to create a humid environment.
For this experiment, I replenished the amount of water in the damp box, with a jug of water.
It’s important when using a damp box that the water doesn’t pool on the top of the plaster. You can dab it down with a cloth or paper towel.
Once the plaster is suitably moist, position your pottery in the box. Make sure that the various pieces are not touching each other. Especially if they are made of a different clay body.
Once the lid is on, it should take 2-3 days to rehydrate bone dry clay fully. Not only is the atmosphere damp, but the plaster is also moist. The clay draws water up from the plaster, without becoming waterlogged
Verdict:
This is my preferred method way to rehydrate bone dry clay. On this occasion, the clay was leather hard and ready to trim in 3 days.
Although it took a few days, it’s quicker than the first method I described. And the pottery is not damaged at all by the process of reviving it.
Advantages of This Method of Rehydrating Bone Dry Clay
Once you have built your damp box all you need to do is keep the plaster moist and put the pottery in the box.
- A damp box is quite compact and a few boxes can be stacked on one another.
- Unlike simply covering your pottery in a bag, in a damp box, your clay is protected.
- Pottery rehydrates evenly in a damp box, which stops moisture differentials from being introduced. If one part of your clay gets soggier than another, it is more likely to crack next time it dries.
Disadvantages
- You have to make your damp box which takes about an hour.
- Once you have made the box, it is a permanent feature in your studio, taking up space. Unlike a plastic bag and towel, it can’t be folded away.
Method 3:
The Bag and Bucket Way to Rehydrate Bone Dry Clay
This is one way to rehydrate bone dry clay in small amounts.
What You Need:
- A bucket of water.
- A sponge.
- A sealable plastic food bag, or one with handles you can tie.
- A piece of dowel.
- A needle tool.
Method 3 for Rehydrating Bone Dry Clay – The Steps
Put your bone dry clay into a sealable plastic bag.
Add some water to the plastic bag with your sponge. Add enough water so your clay is sitting directly in the water and semi-submerged.
Dunk the bottom half of the plastic bag into the bucket of water. This will get rid of the air in the water around the clay. Seal the plastic bag up, either with the zip lock or tie the handles together.
Suspend the sealed plastic bag and clay in a bucket of water. If you are using tie handles you can do this by slipping a piece of dowel through the handles. Then dangle the bag into the bucket.
Make sure that the whole piece of clay is submerged in the bag under the water. The idea is that the pressure of the water forces the water in the bag back into the clay.
When I’ve seen this demonstrated, it has been suggested that you can leave the clay for around 5 minutes. After around 5 minutes, take the bag out of the bucket and open the bag. The idea is that the bone dry clay will now be rehydrated.
Verdict:
I left my clay submerged in the bag for 10 minutes. When I took it out, the surface of the clay was a little pulpy, but it still felt hard. I prodded it with a pointed sculpting tool. I could tell that only 1/8 of an inch was soft.
I decided to submerge it again. This time, I replace the dowel with some string. My intention was to let the clay sit deeper in the water. I thought that more water pressure on the dry clay might help.
However, after another 10 minutes, the clay was still hard on the inside. What’s more, the outside had become quite mushy and bloated.
My conclusion is that this method might work if you want to rehydrate bone dry clay that is quite flat and thin. However, chunkier pieces, even if they are small, don’t seem to fare too well.
Advantages of This Method of Rehydrating Bone Dry Clay
I am aware that this method can work with small flat slabs of clay. When it works it is a quick, mess-free way to rehydrate bone dry clay.
Disadvantages
It doesn’t work well with chunkier pieces. The piece that I tested was a funny little donut shape my daughter had made. But it wasn’t much thicker than the base of a typical pot. I’m not sure how well this method would adapt to reviving something substantial like a bowl.
Method 4:
The Rinse it and Wrap it Way to Rehydrate Bone Dry Clay
I would describe this method as being a seat of your pants kind of technique. I approached it with apprehension! I was pretty certain that the clay was going to simply dissolve in my hand.
What You Need:
- A tap!
- A soft cloth or small towel.
Method 4 for Rehydrating Bone Dry Clay – The Steps
- Run your bone dry pottery under the tap.
- Keep turning it so that each side and surface is under the direct flow of the tap.
- Continue to do this for a few minutes. If you take your pottery out from under the tap too soon, the superficial water will evaporate immediately. And your clay will be dry again quickly.
- Take it out from under the tap once it feels as if it’s been thoroughly wetted. But before the sides of the pot start to go floppy.
- Wet a small towel or rag and wrap the pot in the very wet rag. Don’t use a big heavy towel, as this will potentially damage the shape and surface of your pottery.
- Let this sit for five to 10 minutes. Monitor how damp the clay is at intervals. Once you can make a mark in the underside of the pot with your thumbnail remove it from the cloth.
- Don’t leave your pot in the damp cloth for longer than 10 minutes. If you leave it for any length of time the base will sit in a pool of water. The result of this would be that the bottom of your pot would turn to mush.
Verdict:
My experience of using this method of rehydrating bone dry clay was that it was not very effective. I had expected the pot to simply dissolve in my hands. However, what happened was that the greenware actually stayed pretty hard.
Even though I left it in the cloth for around 20 minutes, it was only superficially soft.
What I also noticed was that the slip that had dried on the surface of the pot was flushed away. This left a rather unappealing gritty sandy texture to it. It didn’t look like a nice grogged surface, it just looked like a grainy mistake!
The Pros and Cons of This Method of Rehydrating Bone Dry Clay
If this method worked, it would have the advantage of being easy and quick. However, I did not find it to be successful.
I’m aware that other potters recommend this approach. But they must be doing something differently. I would not recommend it as a way to rehydrate bone dry clay.
Final Thoughts
This was a useful exercise for me. What I have taken away from this experience is that there is no short cut to rehydrating bone dry clay. I did not find that the quicker ways of submerging the clay in water very effective or speedy.
What I found that putting the clay in a humid atmosphere and giving it time to reabsorb moisture worked. The damp box worked the best, as the clay could draw up water from the plaster without getting water logged.