Concrete Floppies

Sat, 11 Apr 2026 00:00:00 +0000

After finishing my Unregistered Boneheads project, many ideas came to me. Not especially as a full second series of bones, but as a desire to explore new mediums. One of those was concrete.

Some online hobby shops are selling ready to be used small portions of “art” concrete. That’s basically (almost) the same concrete used in your house, but more liquid and very much more expensive. Stubborn as I am, I went to my local hardware store, but without a surprise, all concrete is sold in huge bags of 10 to 30kg. Makes sense.

So I moved to my local hobby shop and found what’s called “Jesmonite”. This is a secret formula of acrylic resin liquid part that you mix with mineral powder, and ends up with a concrete-like material. More expensive than my initial >real< concrete kit, but I took it anyway.

The project

Something I had in mind for a while, was to have (or make?) nice floppy-shaped coasters. Most of what you can find online are crappy plastic shapes, and using real floppies was not what I was aiming for. It felt quite appropriate in my head, having the “premium” feel and touch of soft concrete with an object as iconic as a floppy disk.

I started by finding a cardboard box with matching dimensions to make my silicon casting. Ironically, or maybe poetically, the closer I had was a HDD/SSD enclosure.

I made a wall with LEGO Bricks to reduce a bit the box size and as such reducing the amount of silicon I had to pour. Everything was then secured and made water-tight with tape and hot glue.

My cloning subject was of floppy I had from my childhood. I removed the label, gave it a nice alcohol bath and make sure it was as nice looking as possible. Little holes around the disk were filled with hot glue as I don’t want my silicon to slip into every little hole and make each casting a pain to remove.

Making the mold was as straightforward as you can imagine, tape the floppy to the bottom of the box and pour silicon over it. Making sure everything was covered and trying as much as possible to get rid of bubbles. A night later, my mold was ready to be used.

At this point everything was ready for Jesmonite. Mixing with a ratio of 1(liquid):2.5(powder) by weight, I added a touch of acrylic paint to add some color and poured.

Unlike with my epoxy peripetias, Jesmonite is cured in a matter of minutes, after which I can sand down excesses and stick some rubber feet to the bottom of each.

Beauty shots

Honestly quite happy with the results. My silicon mold have some imperfections which are obviously translated into my replicas. But it’s very close to what I had in mind. Making Jesmonite coasters is probably the Jesmonite 101 activity, however it makes an afternoon well spent and looks quite nice on my coffee table.

I started by doing a bit less of Jesmonite (35g against 42 now), as such two of the floppies broke during manipulation. Nothing unfixable by a bit a glue :)

Recipe

(note to myself, just in case)

Jesmonite:
- 12g liquid, 30g powder
Silicon:
- 80g total

Crafts on Thi's things

Concrete Floppies

The project

Beauty shots

Recipe