This is a fascinating, almost “alchemical” home experiment! When you mix these three ingredients, you don’t just get a mush, but your own modeling clay that hardens into stone when it dries.

It’s essentially a recycling technique that hobbyists call “artificial stone” or particularly durable papier-mâché.

What exactly happens? Polystyrene (Styrofoam): While it doesn’t completely dissolve in hot water (you would need acetone for that), the heat and mechanical stirring cause it to shrink and lose volume (air).

Toilet paper: It adds cellulose fibers to the mixture, which act as a “framework” or binder.

Hot water: It helps the paper fibers dissolve into a fine pulp, which is then coated with polystyrene scraps.

What is the result and what is it good for?

If you mix this mixture well (ideally with a little white PVA wood glue), you will get a malleable mass from which you can make the following:

Garden decorations: After drying, the mass is surprisingly light, yet very strong and weather-resistant.

Artificial rocks and stones: Ideal for aquarium enthusiasts (caution, the glue is toxic!) or model makers creating dioramas or nativity scenes.

Repairing holes in walls: In an emergency, this mixture can be used as a very strong filler that can be sanded after it hardens.

⚠️ Important note: Be careful when handling polystyrene and hot water. Polystyrene can release microplastics or fumes at high temperatures. Therefore, work in a well-ventilated area. To achieve a truly “liquid” polystyrene effect, some people use acetone instead of water. However, this is a dangerous chemical reaction that produces an extremely flammable “plastic slime.”

Would you like me to put together a precise “recipe” with the exact quantities needed to make a smooth, crack-free modeling clay from this mixture?