Cover your work area with a plastic mat or with newspapers. Find a mixing container (preferably a disposable one) that could accommodate the amount of mixture intended.
The ideal ratio for a plaster of paris mixture is 2 parts plaster of Paris powder to 1 part water. Measure out the water and pour it into your mixing container.
Measure out the plaster of paris powder and put it into another container. Break up any lumps of powder with a spoon.
Remember that the ratio should be 2 parts powder to 1 part water. If you measured out 1 cup of water in Step 1, then you would need 2 cups plaster of paris powder.
Continue adding the Plaster of Paris powder, tapping the sides of the container from time to time. The cue to stop is when you notice that the powder is almost covering the surface of the water and is not as easily absorbed by the water. Normally this point would be around the 2:1 ratio but could vary slightly depending on several factors, including the brand of plaster of paris powder and water temperature.
The mixture will start to set within a few minutes. Besides hardening, you'll notice that the plaster of paris also gives off heat. It typically takes 20 to 30 minutes for plaster of paris to set.
*The drinking straws on this particular project is to create a hole on each plaster of paris cube.