I did this at TechShop Menlo Park. http://www.techshop.com
In order to save time, money and materials instead of using plastic buckets for mold containers and having to cut them and recycle them, I decided to make a reusable collapsible mold box.
Step 1: Take measurements
I took measurements of the sprued wax object I am trying to make a plaster mold for. It was 7 by 7 inches so my mold box needs to be 8 by 8 to accommodate it with some space on all sides. My object including the main sprue was a little over 9 inches so my box needs to be 11 inches in height to safely fit the object without risking it touching the bottom. 2 of the sides need to be slightly wider then the other two so they nicely overlap.
Step 2: Putting together
i found some wood in the scrap bin and cut it to my pre- planned dimensions. I put the pieces together with tape so I can easily take the tape off and collapse the box to get the mold out saving my box pieces to reuse it many times over.
Step 3: Object insertion
In order to keep my sprued wax object hovering in the middle space of the box to pour plaster into, I stuck a piece of welding wire into its base and hung it into the box and poured plaster over it.
Step 4: Cure the mold
After taking the box apart to reuse many times over I bake the plaster molds in a kiln very slowly increasing the temperature to prevent them from cracking from heat shock by turning the kiln to low, taking all the peephole plugs out and propping the lid open with shelf supports. My box made many molds and saved much plastic waste.