This Instructable will be part of a series that will start by looking into creating minimal surface’s using sand and the process to do so, from creating a container to do the tests in to how the surface responds to different parameters, and how to solidify a layer of the geometry.

There are multiple ways to use this process, I will be going into detail on two ways, the first using sand mixed with salt and spraying it with salt water, the second using hairspray to create the bond.

Materials:

Quikcrete (or other PlaySand)
Box Created for Castings
Razor Blade
Salt (Sea salt seemed to work best)
Warm Water

Measuring Cup

Table Spoon

Tea Spoon

Spray bottle

Step 1: Create Your Geometry

The first step when doing this process is to decide upon the geometry that you will be using. For early tests to make sure you get the process done correctly and the mixtures you want you can use just a pile of sand. This will make it for easier remove of the shell. I recommend doing this on either an edge or corner of the box you created so you can remove the walls allowing you to see how the shell has formed and making it easier to remove.

Depending on the way you want to solidify your model will depend on the sand you should use. For my tests I used Quikrete (Play Sand), which is just a playground sand found at ACE hardware.

Note: Make sure your sand is completely dry before attempting

If you are going to use the Salt water mixture first mix in salt with your sand, this will help make sure that there is a strong bond between particles creating a stronger shell. I found that a mixture of 10 parts sand to 1 part salt worked well for me.

If you are going to use the hairspray you can just use the sand by itself, but if you have created a large amount of the mixture of sand and salt you can use that as well.

Step 2: Create Your Agent

If you are using the Hairspray make sure you have a bottle with a high strength hold, for the Salt water you need to do a little more preparation.

What you'll need:

Salt (Sea salt seemed to work best)

Warm Water

Measuring Cup

Table Spoon

Tea Spoon

Spray bottle

Depending on your sand mixture and salt you may need to experiment with the Ratio of water to salt. For my tests I used 2 cups of warm water and 3 Tablespoons of Sea salt.

Step 1: Pour 2 cups of warm water into a measuring cup

Step 2: Add 3 Table Spoons to the water and stir until completely dissolved.

Step 3: Pour the solution into the spray bottle.

Step 3: Spray Your Geometry

Use the correct agent to spray the geometry. For this step you will want make sure you cover the geometry completely and with a few coats without over saturating the sand, between 3 to 5 passes seemed to work without over saturating for me, but using the hairspray this isn't as much of an issue. If you do end up over saturating it, you will just need to allow more time for the sand to dry completely.

Note: to speed up the drying process a hot light or a heat gun work really well.

Step 4: Remove the Geometry

Carefully remover the sides of your box, use an Razor Blade if needed to carefully cut along the edges, breaking the seal from the sand and your box. Slowly start to remove the sand from the underside of the shell until the majority of the sand is removed. Try lifting the shell, if it is stuck use the razor to cut the area free where it is attached.