Question about sand form

[bnew17]

I have been going back and forth on whether to make a hard form for my oven or make a sand form. I have access to both sand and red clay. Is the red clay desirable to make the “sand form” ? I would assume so since it gets hard. The sand is mostly dry but there is some with some moisture.

There are so many topics with “sand” and “form” a when searching I have had a hard time trying to find a good thread on this topic.

[david s]

The advantage of the sand form is that it is easy and fast to create as well as easy to remove.. It only needs to be in place as a temporary form. Making it from clay will introduce problems of the clay shrinking as well as being really difficult to remove. A sand castle allows you to cast in situ rather than having to move the heavy casting and risking damage.Using wet newspaper as a slip layer to stop sand adhering to the cast can result in it slipping, creating folds and exposing tsome of the sand to the castable. You can try a 50/50 mix of water and PVA to hold the newspaper together where the bits overlap, like a really thin paper mache layer that wouldn't be too hard to remove out the oven mouth.

[bnew17]

The advantage of the sand form is that it is easy and fast to create as well as easy to remove.. It only needs to be in place as a temporary form. Making it from clay will introduce problems of the clay shrinking as well as being really difficult to remove. A sand castle allows you to cast in situ rather than having to move the heavy casting and risking damage.Using wet newspaper as a slip layer to stop sand adhering to the cast can result in it slipping, creating folds and exposing tsome of the sand to the castable. You can try a 50/50 mix of water and PVA to hold the newspaper together where the bits overlap, like a really thin paper mache layer that wouldn't be too hard to remove out the oven mouth.

Thanks David, is there a certain type of sand that is recommended?

[david s]

The cheapest.
As almost all kids discovered, making sandcastles works with most sand, but finer sand forms more readily. Around 10% water is about right and the addition of some powdered clay helps it stick together. But that is really not required as it’s a hemisphere you’re making with no undercuts. Some polystyrene fruit boxes or similar piled into the middle reduces required volume of sand.