🧫 Mycelium Casting Instructions

Ashley Goldbirch
Sep 16
3 min read

This is an brief instruction list for casting with our mycelium substrate. Outcome results of mycelium will naturally vary due to its living nature. These parameters are as a guide and do not represent all the possible methods to cast and grow mycelium materials!

🧰 Equipment Needed

70% alcohol (preferred for sterilising) or soap and water
Gloves (especially if you are sensitive to alcohol)
A mould or form (plastic, glass or metal is best; avoid wood or porous materials)
Distilled or de-ionised water (tap water also works)
Clingfilm (plastic wrap)
Micropore tape (surgical bandage tape)

⚙️ Instructions for Use

1. Prepare the Mould

Clean your mould thoroughly with soap and water, or wipe with 70% alcohol.
Make sure the mould is completely dry before use.
Use non-porous materials (plastic, glass, metal) to prevent the mycelium from bonding to it.

2. Prepare Water

Set aside some distilled or purified water in case your substrate needs rehydration.
This will help prevent contamination during the process.

3. Break Up the Substrate

Clean the outside of your substrate bag.
Gently break apart the material inside without puncturing the bag.
If there are large clumps, remove them when packing the mould to ensure even growth.

4. Clean the Workspace

Disinfect your work surface.
If possible, work near a lit gas hob to create a cleaner air zone (but keep alcohol away from open flames!).

5. Check and Adjust Moisture Content

Cut open the top of your substrate bag.
Take a handful of substrate and squeeze it:
- If dry and crumbly, add water gradually (about 100 ml per 500 g substrate) and mix well by shaking the closed bag.
- It should be moist enough that water comes out when squeezed, but not dripping wet.

6. Pack the Mould

Gently press the hydrated substrate into your mould.
Do not compact too tightly—this can suffocate the mycelium in the centre.

7. Cover with Clingfilm

Wrap the mould with clingfilm.
Heat the tip of a toothpick or knife and pierce small holes through the clingfilm (about every 5 cm apart).

8. Apply Micropore Tape

Cover the pierced holes with micropore tape.
If you don’t have micropore tape, you can cover the mould with a paper towel soaked in alcohol.

9. Incubate

Place the mould in a warm (19–25 °C), dark place away from direct sunlight.
Incubate for up to 2 weeks, checking periodically.

10. Remove from Mould

When the material appears fully colonised and white throughout, gently remove it from the mould.

11. Optional Surface Growth Stage

If desired, place the piece in a moist, closed container to let the mycelium thicken on the surface.
Note: mushroom fruit bodies may appear during this stage.

12. Drying

Bake your mycelium piece in an oven at 60 °C for 2 hours to kill the living mycelium.
Afterwards, place it somewhere warm and breezy to remove remaining moisture.

13. Finished!

Your mycelium object is now complete and ready to use.

⚠️ Safety Notes

If you notice strange growth or colours, it may be mold contamination.
Spray the affected area lightly with hydrogen peroxide (H₂O₂) and allow the mycelium to regrow over it.
If contamination spreads, wear protection and open the bag in a well-ventilated area—some molds can be harmful when inhaled.
Always be extremely careful when working around an open flame, alcohol is very flammable, if you don't feel confident, complete without the use of an open flame or ask for assistance. Goldbirch is not responsible for any harm from accidents.

♻️ Aftercare & Disposal

If your creation reaches the end of its life, break it up and mix it into topsoil or compost—it will decompose in about 3 months.
If it gets wet, dry it in a warm, breezy spot.
Be gentle when wet, as the mycelium skin can be impressionable.

Enjoy creating! If you share your creation online, tag @gold.birch on instagram — we love to see what you make!