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:
- 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.
- A storage box, this is what I’m currently using - 58L Sealed Storage Box
on wheels ($30, from The Warehouse)
- Water (as per the plaster instructions).
- Measuring jug
- Face mask
Steps to Make Your Damp Box:
- 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 😊
- 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
- 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
- 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.
- 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.