Flexible and Light Stone Material





Introduction: Flexible and Light Stone Material

By experimenting with foams and sand I found out that it's really easy and fun to make a material I call "sandy foam'. It looks like stone, but is actually a flexible and light material. It's perfect to decorate your garden or home with and to make projects with (not too young) children.

This Instructable is about the basic steps of making the material and the experiments I did. In the end I explain how to use the material for making products.

Step 1: Ingredients of the Material

All you need are two components of expanding, flexible foam and sand. I used the flexible polyurethane foam of Dougles & Sturgess. And sand from Ocean Beach of San Fancisco, to add an extra personal touch to the material. The materials you use are really important for the look of the material. The structure, flexibility and color of the material depends on it. Take a look at step 4 for the experiments I did with different kinds of foams.

Step 2: Measure the Ingredients

The basic amounts I used were 0.10 oz of part A, 0.30 oz of Part B and 1.30 oz of sand. But the proportions depends on which materials you are using and what kind of look you want to achieve.

Step 3: Mix the Ingredients

Mix part A and B together and add bit by bit the sand.
In total, mix at least 30 seconds. It is recommended to use a drill for the mixing, because it will stimulate the expanding process. But I just used my hands for mixing and it also works fine.

Step 4: Experiments With the Material

I experimented a lot with the sandy foam.

The first picture shows the different expanding foams I used and the different amounts of sand. I used expanding foam because, first of all, it's a little bit magical to see the foam growing. Also, it will shape itself in a organically looking shape, and that is useful if you want it to look like stone.
The top layer is made with Soama Foama 25 of Smooth-on and the second layer with flexible polyurethane foam of Douglas & Sturgess. The first one expands less, is more flexible and sticky and has a smoother surface. I decided that the second one is more suitable for the stone look.

By working together with Alex Crease (printeraction) we created this ball shape, you can see in the second picture. Alex 3D printed a mold and first we poured a little amount of sandy foam in it. After that layer dried we poured another amount of sandy foam in it, this time with less sand in it.

The third picture shows experiments with molding the sandy foam. I found out that if I didn't cover it with any material, like paper or textile, the foam gets shiny and less stone-like.

Using molds made from different materials, like plastic, paper and foam, I learned that the sandy foam is really sticky and needs grease, like molding release, to get from the mold easily.

Step 5: How to Use the Material

Because the material has a stone look, I used it for products for the garden or a home. Like flower pots, bowls and fake stones.

Here's an Instructables about how I made the flower pots: Flexible Stone Pots.
This Instructable explains how to make fake stones: Fake Stones.
And these bowls are fun to make too: Flexible Stone Bowls.

Let me know if you have any creative ideas for a sandy foam project!



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    12 Discussions

    Do you find that this material is porous? I wonder how well it would work to make a container for earth and plants in a terrarium, then fill in the rest with water. I have frogs and am looking for options. If I experiment with this I'll let you know.

    It's a great idea! Thanks for sharing.

    1 reply

    Or you could make a floating island for a fish tank.

    perfect for my front garden where I want a few nice rocks that cant be used to brake my window in :) (Yes, I live in a rough neighbourhood and dont want my window braking)

    1 reply

    Great idea. I made an Instructable about how to make fake stones with this material: www.instructables.com/id/Fake-Stones.

    Great idea....I'm wondering if you've experimented with these on a larger scale, and how they hold up long term to light and water....as in garden troughs and small ponds for rock gardens....

    Did you flush your sand with plenty of water to wash it since you got it from the beach?

    This is a neat idea. It would be a good way to transform my sand collection (I collect sand from every beach I visit) into something new!

    1 reply

    This sand looked very clean and without rocks or shells, so I didn't wash or sieve it.
    That sounds like a great project!


    3 years ago

    This would be great for making film props and sets. Really great idea!

    Very cool! I'm curious how the material will hold up over time and UV exposure.