Flexible Stone Pots





Introduction: Flexible Stone Pots

Looking for a way to decorate your garden or house? These pots have a stone look, are flexible and light and the best thing: they are easy and fun to make!

The pots are made from a material I call "sandy foam". A combination of expanding foam and sand. More explanation about the material I used for this pots, experiments with it and all the possibilities, look at my previous Instructable: Flexible And Light Stone Material.

Step 1: Grease Cups

To create the pots, we're going to "flatten" the sandy foam between two cups. You need two cups that fit into each other and give the foam enough space to expand and shape around the smaller cup.
Grease both cups in with mold release. I used grease from a "Body Double" package of Smoot-on. Grease the inner side of the bigger cup and the outer side of the smaller cup.

Step 2: Mix Ingredients

For the sandy foam material I used flexible polyurethane foam of Douglas & Sturgess. To create the foam for the first layer I used 0.10 oz of part A, 0.30 oz of Part B and 1.30 oz of sand. Mix it for at least 30 seconds, and add little amounts of sands in between. I mixed it in a smaller cup to make it easier to pour the foam into the greased bigger cup. The foam is pretty thick and sticky after mixing, so I needed a little help of two spoons to get all the material into the bigger cup.

Step 3: Build First Layer

Once you poured all the sandy foam into the bigger cup, press the smaller cup into the bigger cup to flatten the foam between the two cups. You can see the foam shaping itself around the smaller cup. Using a transparent cup makes it easier to keep track of where the foam is going.
As the foam is expanding, it will press the smaller cup upwards. To make sure the smaller cup will stay in the foam, you can put something heavy in or on the cup.
Wait until the foam is dry and take the smaller cup out of it. This shouldn't be too hard if you greased the cup.

Step 4: Build Second Layer

In case you want to make a second layer, let the dried sandy foam stay inside the bigger cup. Building a second layer can be interesting if you use lighter or darker sandy foam. You can achieve this by mixing more or less sand with the foam. For a lighter second layer I mixed 0.30 oz into the same amount of part A and B as I used for the first layer.
Smear the lighter sandy foam above the first layer around the edges using a spoon or mixing stick. Now press again the smaller cup into the bigger cup, wait until the second layer is dry and pull the smaller cup out of the foam.
The most easy way to remove the dried sandy foam from the bigger cup is to cut the bigger cup and tear it until the bottom, so the cup opens up and you can easily remove the dried sandy foam from the cup.

Step 5: Result

A stone looking cup appears when you remove it from the bigger cup.

Step 6: Experiment!

Experiment with different molds and shapes and amounts of sand. I discovered that when you do not grease the bigger paper cup (the white cup I'm using in the previous steps), the sandy foam will attach to the paper. Removing the paper from the dried foam is difficult, but it creates a very interesting and rough structure, see the last picture.



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    20 Discussions

    Does it hold moisture or do you have to use a tray underneath?

    Suppose, this foam is not particularly ecologically friendly... 8(
    So, a no-go for me (many more, maybe) until other gluing substance invented or found...

    5 replies

    Is this a fact or a concern? Is it toxic? Is the foam safe to handle with bare hands? Just the facts please!

    Imho, it's just constructive criticism, not negative nor positive.
    Maybe, it'll spark motivation/idea to find some other substance instead of the one used here...

    An interesting project. Where can we find black sand like you used in this instructible? The only sand I've ever seen in my country is white or tan color.

    4 replies

    I've found it at Ocean Beach in San Francisco. I don't know where you live, but it's definitely worth a trip to San Francisco ;). You could also take a look at for example Amazon, for decoration sand.

    I would venture that the darkness in the sand particles is crushed carbon, from beach bonfires. (as an SF native).

    That could be the difference. Hmmmm, maybe a crumbled charcoal briquette could adjust the color of play sand to get this look. Thanks

    I lived in San Francisco back in the early '80s. The sand on Ocean Beach was tan back then. Maybe I can buy colored sand at the craft store. Thx

    How do you recycle the PET after the pot is no longer needed or useful?


    Excellent instructable! It will be interesting to see how sturdy and flexible this material is. For instance, how big of a pot one could make and whether or not one could move it around without it falling apart...how flexible it is...things like that.

    Actually...just the idea appears worth the purchase of materials, even without a specific project in mind...just to play with and test :)

    These pots kind of resemble a part of a sandcastle at the beach. (Which makes sense, given that they are 3/4 sand.) I like the look! Nice idea. :)

    1 reply

    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....

    1 reply

    Thank you! I haven't used the material for larger projects. But I can imagine you can create garden troughs by using buckets or tupperware boxes as molds, instead of cups. That would be a really interesting project.

    This is a cool idea. I really like the look.

    Beautiful idea to mix fine aggregate into a foam base material, thanks for the inspiring idea!