Step 1: Find a mold
There are several sources for these molds readably available if you know where to look for them. We have only tried this with soft silicone molds so far, but other types of molds may work as well. If you look in the clay section of crafts stores it is possible to find molds for making clay leaves and flowers. These can frequently be repurposed to make war gaming terrain. Molds that were intended to make edible plant parts for cake decorating are also an excellent source.
Step 2: Make a cast
Once you have a suitable mold you will need to make a hard casting of the desired objects. We started by making a casting of the mold in dental plaster (what we happened to have on hand). We then added some handles to the back side using some dowel pieces, with a little wood putty used to support the back side of the oddly shaped casting. If you are pressing something large this isn’t really necessary, but if it’s small you will need a handle large enough to hold onto.
Step 3: Find some plastic
Next you will need a good supply of suitable plastic. We cut our plastic off some old packages that we had lying around. Any blister pack you have on hand should work. Not all clear plastic is suitable for this however, so make sure that it turns soft and pliable when heated. Don’t bother trying to use plastic cut from a beverage bottle because it will not work.
Step 4: Shape the plastic
Once the plastic is cut into appropriately sized pieces that are large enough to hold. The plastic is then heated over a candle until it becomes soft and is immediately pressed into the mold using the casting. It takes a little practice to get the temperature just right, but isn’t too difficult. Basically if you get it too hot you melt a hole in it, and if it’s too cool then you don’t get any detail from the mold. As long as it’s warm enough to be pliable it will work. Repeat the process as many times as necessary, trim, assemble, and paint.
Obviously this process will work for many things besides making plants. I got the original idea for it from somebody who was using the process to make clear plastic canopies for model airplanes. http://www.ffscale.co.uk/page4f.htm