One of the first replacements we found when starting the studio was mushroom foam. Made of mushroom mycelium, it is a plastic-free casting medium that you grow yourself. Grow.bio by Ecovative offers dehydrated material that anyone can buy and lots of educational material and inspiration to help you get started.

Founder Melissa had an inkling that this could replace styrofoam for set-making, but there was only one way to find out! Instead of doing testing, we jumped right in and got enough material to grow the farm set for our short film. Working on such a large scale made the process a bit different, but Grow.bio’s team was always quick to offer advice when we weren’t sure how to proceed.

While this is somewhat of a finicky process, it’s incredibly rewarding when you are successful. Here is what we learned and how we were able to use their innovative material to replace all styrofoam for our short film sets.

• Bag of Grow.bio dehydrated mycelium material
• 3 cups filtered water
• 8 tablespoons organic, unbleached white flour
• Bag of Sculpting mix (optional)

(Each bag of material fills approx. 0.12 ft³ of space. You will need to calculate how many bags of material you need for your project and multiply the above amounts by that number)

• Extra Large stainless steel bowl
• Spray bottle of 70% Isopropyl alcohol
• Compostable gloves
• Binder clips (2 per bag)
• Compostable cling wrap
• Mold(s) in the shape of your choosing
• Plastic bag or tarp
• Glass dish, filled with filtered water
• Humidifier (optional, depending on region)

1. Spray alcohol over your workspace and allow to dry or wipe clean.
2. Open the bag of dehydrated mycelium material. We like to cut the top off with scissors, but make sure not to rip or damage the white square on the bag.
3. Put on your gloves and mix 4 tablespoons of flour and 3 cups of water in a bowl. Then pour it into the bag.
4. Realign both sides of the bag and fold it down until it’s just above the white square. Use two binder clips to re-seal the bag.
5. Carefully holding the folded edge and the bottom of the bag, shake rigorously until the mycelium material appears to have evenly absorbed the flour and water.
6. Repeat this process for as many bags of material as you have.
7. Store in a clean, dark room with the temperature set to about 72 degrees Farenheit for 3-4 days or until the material grows a white layer all over it.
8. Bring back to your clean surface and spray the stainless steel bowl with alcohol. Wearing gloves, open one bag and pour the clump of material into the stainless steel bowl. Break up the material with your hands until it’s back into small pieces. Make sure to only do one bag at a time.
9. Add 4 tablespoons of flour and mix. If you are going to be free forming this onto a set, add the sculpting mix here.
10. Prepare your mold (see notes below) and pack the now-fed material into it OR begin forming natural shapes on your set. Continue steps 8 and 9 until all of your bags are used. Cover in cling wrap, making sure it doesn’t touch the material, and poke holes in the cling wrap with a toothpick.
11. Place the mold back in the temperature controlled room and leave for 5-6 days or until it is white again.
12. Carefully release the material from the mold and, if it’s small enough, place it in a plastic bag or drape a plastic tarp over the form so that it isn’t touching the material. Fill a glass cup, bowl, or dish with filtered water and place it under the bag to keep it moist. Make sure the plastic is secure enough to seal the moisture from the dish in.
13. Check back the next day and continue checking until a white layer has grown all over the form.
14. If it’s small enough to fit in an oven, place it on a baking sheet and bake at 180 degrees Farenheit for a few hours or until dry. If it isn’t small enough, store it in a low moisture area and continually check to make sure no new growth occurs.

• It’s very important that you don’t damage the white square on the Grow it Yourself bag. This is a filter and prevents the material from molding while it rehydrates. Once we were able to fix a rip with duct tape, but another time it ruined a whole batch.
• We made our molds out of wood secured with screws and lined the bottom with cardboard covered in cling wrap. We also lined the wood sides with cling wrap to ensure we could easily release the grown material from the mold. If needed, we unscrewed one side of the mold to get the material out.
• To make the natural landscape shapes on our 4×8′ set, we covered cardboard in cling wrap and taped it to the edges to contain the material. We also used the sculpting mix to help form the hills and ground. Adding this cardboard container also allowed us to cover the entire set in cling wrap without it touching the material.
• You can poke toothpicks into the foam in step 12 so the plastic bag can rest on the toothpicks instead of directly on the foam.
• Montana is a very dry climate so we needed a humidifier to keep the room moist enough to grow the material. If you live in a very humid place, you won’t need a humidifier.
• If you live in a humid place and are growing a form too big to dry in the oven, you may need to look into a dehumidifier so that the mushroom foam doesn’t continue to grow. If it does, you will start to see black spots on the white outer layer.
• The one beef we have with this process is the necessity of a plastic bag. We did try using a plastic tarp, but it was too large and wasn’t sealing the set in well enough. We do think this could work, but it was too early in our R&D to take a chance so we did get a a roll of painter’s plastic, which we used as sparingly as possible. Grow.bio said we could reuse this if we cleaned it with bleach, but since bleach does not align with our studio values, we opted to reuse what we could. (If there are no holes from toothpicks and the plastic didn’t touch the material, we were able to reuse it without issue.)
• We grew anywhere from 5 bags to 30 bags at a time. You will need enough to fill out your entire mold or set in one go, you cannot add to the shape once it starts growing. We would always recommend growing a little extra, as you can always make a smaller form from it.
• PAY VERY CLOSE ATTENTION TO THE EXPIRATION DATE ON THE BAG. You must use the bag within 10 weeks of the batch date, not the date you received it.