We need to prepare some materials: silicon dioxide, polyvinyl alcohol, glycerol and water. These materials are relatively safe and easily available.
Silica and polyvinyl alcohol are mixed in the ratio of 1: 1. You can adjust the amount of material as needed to obtain the required colloid concentration. Then, add proper amount of glycerol and water to the mixture.
Next, put the mixture into a container and stir it thoroughly with a stirring rod or stirrer. You will find that the mixture becomes sticky and bubbly, and you can pull the filaments with your fingers.
When the mixture is stirred evenly, pour it into a sealed container and let it stand at room temperature for a period of time. This can further solidify and shape the mixture.
After standing for a period of time, you can use this styrofoam without clay, borax and glue. It can be used for some simple bonding tasks, such as the bonding of paper and cloth. Please note, however, that the adhesive strength of this kind of styrofoam may not be as good as that of commercial rubber, because no clay or adhesive is added.
Making styrofoam is not complicated, and clay, borax and glue are not needed. Just prepare silicon dioxide, polyvinyl alcohol, glycerol and water, and mix and stir them according to a certain proportion. Although its bonding strength may be limited, it is completely feasible for some simple bonding tasks. I hope this method can meet your needs!