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Making a damp box for your pottery pieces

At that start of Summer, I made a damp box to store my pottery pieces with the hope it would slow down the drying process and give me time to trim and attached handles etc. It has worked amazingly. Pieces I made weeks ago still feel like they have just been thrown. So, I thought I would make another damp box, to help show how easy it is. Takes about 10min to make (honestly, I should have made one as soon as I started pottery)

What is a damp box?
A damp box is a sealed container with a plaster base that helps keep unfinished pottery in a workable state, preventing it from drying out too quickly.

I’m based in Auckland, NZ so I’ve sourced the products from my local suppliers.

What You'll Need:

  1. Plaster of Paris (I use the entire 5kg bag – nice and easy). Bunnings has it at limited locations, Gordon Harris stocks it, and Placemakers has it ‘direct from suppliers’ – so you just need to order it in.
  2. A storage box, this is what I’m currently using - 58L Sealed Storage Box on wheels ($30, from The Warehouse)
  3. Water (as per the plaster instructions).
  4. Measuring jug
  5. Face mask

Steps to Make Your Damp Box:

  1. Find the ideal Storage Box: Things to consider
    • Good height clearance once you have added in the plaster base
    • Find a storage box that has wheels, makes it easy to move around
    • Clay likes to be out of the sun, and ideally in dark and cool spaces, so I choose a plastic box with a black tint. I also keep it covered with a towel
    • If you use a new plastic box even better as it will still have its wax coating on – which allows your finished plaster base to also pop out of the box and to be used as a plaster bat to reclaim/recycle your clay 😊
  2. Mix the Plaster of Paris with the water:
    • For a container this size, I used the entire 5kg bag. Plaster of Paris expands slightly as it sets, but the effect is very subtle—especially over a large surface like a damp box. This means the amount of plaster you mix is almost exactly what you'll end up with.
    • The recommended method is to add the Plaster of Paris to water
    • Stir well with your hand until the mixture is smooth and free of lumps. To avoid air pockets, tap the outside of the box. NB: I still got air pockets
    • Gentle tap the box on the floor/bench to remove more air pockets and to help flatten it
    • Be careful of the wind if you decide to do this outside
  3. Let the Plaster Set:
    • Allow the plaster to set. If you want to pop it out of the container to use as a plaster bat, you can gently do this after 1-2 hours. NB: The plaster will set within 30min, it will feel firm but is fragile.
    • How long to leave it before using – for my initial one, I left it for over a week, this time round, I only left it for 24 hours as I needed to use it. Please follow the specified time on the plaster packaging.
    • Ensure good airflow to help it dry out properly
  4. Activate the Damp Box:
    • To activate, lightly mist the plaster base with water using a spray bottle. The plaster will absorb and retain moisture, creating a humid environment.
  5. Store Your Ceramics:
    • Place your unfinished pottery in the box. Ensure the lid is sealed to maintain the humidity, and add in a pot of water

Tips for Use:

  • Re-moistening: If the plaster starts to dry out, mist it again lightly with water.
  • Cleaning: Avoid soaking the plaster, as too much water can cause it to crumble over time.