Designing Custom Mycelium Molds for Fragile Glass Packaging
What CAD designers and packaging engineers need to know before submitting their first mycelium mold spec to a grow facility.
Designing for a living material
Mycelium isn't injection-molded. It's grown. The mycelium colonizes a substrate (hemp hurd plus agricultural byproduct) inside a void, then is heat-killed and finished. That biology imposes three design constraints injection designers rarely think about.
Constraint 1: Wall thickness
- Minimum: 12mm
- Sweet spot: 18–25mm
- Maximum without internal voids: 60mm
Thinner walls don't fully colonize; thicker walls grow unevenly.
Constraint 2: Draft angles
A 2–3° draft on every vertical surface lets the finished part release from its growth tray. Zero-draft walls work but require split tooling and add lead time.
Constraint 3: Growth tolerances
Expect ±1.5mm dimensional variance on parts under 200mm, ±3mm above. If your glass bottle requires a press-fit, design the mycelium cavity 1mm undersized — the natural compression seats the glass without rattle.
File format
Cerda accepts STEP, STL, and parametric Fusion 360 archives. Send the glass CAD too — we model the negative around your actual product, not a nominal envelope.
Lead time
- Tooling: 5 business days for new molds under 8 cavities
- First production grow: 7 days
- Total from PO to pallet: 14–18 days
Free DFM review
Send any current EPS or molded-pulp design to Cerda and we'll return a mycelium-converted CAD plus a sample within 10 days at no charge.
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