Montessori Land and Water Form Trays DIY post

So I have been steadily working on building my montessori materials up to get them ready for our new classroom which is about halfway done now!  Here is a look at my finished land and water form trays which all told cost me about 20 dollars to make and are metal instead of the plastic ones that run over 100 dollars for the set!

Materials used:
Plaster of paris
Aluminum cake pans (98 cents each at walmart and the perfect size!)
Modge podge high gloss sealer (to make them waterproof)
99 cent rose art modeling clay (to form the molds for the plaster)
Acrylic paint

I forgot to take in progress pics so I will just give a brief explanation of how I made them.

First I set out all of the trays and rolled out my modelling clay into flat pieces to form the molds,  Then I put the clay into each pan into the shape of the landform I was making.  NOTE: i only had to make 5 total molds as the other 5 trays are the inverse of the first 5 molds which saved on clay and time.  I then mixed the plaster and poured the molds.  Be prepared to hold up the clay for a few minutes on a couple of the molds for stability.  Soon as I pour I tap the whole tray off the table to bring air bubbles to the top instead of inside the plaster.  After it was dry enough I removed the clay and set them up in the next 5 trays and repeated the process but inverted where I poured the plaster. NOTE: on some of the smaller forms you may have to glue down the plaster to the tray after it has set because it will not stick on it's own.  (the ones I glued where: island, peninsula, archipelago and isthmus)  After all the plaster was poured and the clay removed I began painting the trays.  I used green for the top of the land, 2 shades of brown to show the earth on the sides of the land and then blue for the water areas.  I waited a day for them to fully dry.  After they were dry I took them outside and gave each of them a heavy spray down with the high gloss sealer so that my trays can be filled with water when we use them.

here are the finished trays!