Plaster of Paris is a gypsum-based cement-like mixture used in crafts and moulding. Unlike cement, it remains fairly workable with tools after hardening, making it a common choice for creating statues, models and various other crafts. Plaster of Paris is usually bought in a powdered form that is then mixed with water just like cement would be. You can also replicate some of its qualities with common household ingredients.
Mix two parts regular white glue with one part warm water in a bowl, and stir continuously with a wooden spoon or Popsicle stick. Add more water if the mixture is too thick: the goal is to get a soupy-looking product that will still have the consistency of glue. This glue plaster has many applications. Pour the liquid into a mould and let it harden to create 3-D models. Or soak newspaper in it and create paper mache objects.
This glue mixture is an excellent substitute for plaster of Paris, but it is not an exact replication. Drying time is greatly increased, and the finished product won't have the same hard, chalky feel and look to it. Glue-based plaster is best used for wet application to models in the form of paper mache.
Mix two parts standard white flour with one part warm water. As with the glue mixture the key is to thoroughly and continuously stir the mix until all the flour lumps are gone and the mixture reaches the necessary smooth consistency. The liquid should be relatively thick and resemble a glue, but not so thick that it requires great effort to stir it; thin by adding a little more water in very small amounts if necessary.
Flour plaster can be used in the same way as the glue mixture for wet application to newspaper or gauze for paper mache models. Like the glue, flour plaster does not fully replicate the qualities of plaster of Paris. However, unlike the glue there are additional steps to take to better replicate the end result of plaster of Paris. Once the flour mixture is ready for use, allow it to dry and cool somewhat. It will not completely harden, but will turn into a workable solid somewhat resembling bread dough. Shape this however you'd like: try filling a baking tray with the mixture and pressing imprints into it to create things such as handprint moulds or simply tear off pieces and shape them into various objects. Then bake them at around 107 degrees C for several hours and you'll be left with hardened objects that very closely resemble the finished product of plaster of Paris.
Plaster of Paris Mix
Sometimes you may find that there is no alternative for true plaster of Paris. Because plaster is gypsum-based, it has applications that cannot be achieved by glue or flour methods. Fortunately, plaster of Paris mix is relatively cheap and just as easy to mix as any of its alternatives. Combine the mix with an appropriate amount of water, as specified by the packaging. Use a stick or heavy spoon to stir until well mixed; you will have a thick paste similar to the glue mixture but heavier. This plaster mix can then be poured into moulds or sculpted over a rigid structure to create masks, figurines and so forth. Once moulded or poured, it takes about an hour to dry into a solid, but it's best to leave it for an entire day to dry completely through.
For added colour to your projects you can stir a small amount of paint into the plaster mix. One colourful plaster project that's fun for kids simply cannot be replicated with plaster alternatives, because it requires the chalky qualities of actual plaster of Paris. Add colour to the plaster mix and pour it into moulds made of toilet paper tubes. Once the plaster hardens, cut away the tube and the resulting product can be used as sidewalk chalk!