Parafilm
Grow supplies
by Bemis
Parafilm for Mushroom Growing and Lab Work
Parafilm is a semi-permeable sealing film that keeps contaminants out while letting gas exchange happen naturally. Originally a laboratory staple for sealing Erlenmeyer flasks and petri dishes, it's become one of the most useful bits of kit in any mushroom grower's toolkit. The film is 10 cm wide, stretches to 3–4 times its original length, and moulds itself around virtually any container shape you throw at it.
Which Roll Size Do You Need?
We carry two variants. The 1-metre cut is your best bet if you're sealing a handful of petri dishes or agar plates for a single project — enough for roughly 8–12 dishes depending on how generous you are with overlap. The 38-metre roll is what we'd pick if you're doing any amount of regular work. At nearly 40 metres, it'll last months of agar transfers, grain jar prep, and dish storage. Once you start using Parafilm, you go through it faster than you'd expect.
Specifications
| Spec | Value |
|---|---|
| Width | 10 cm (approx. 4 inches) |
| Length (small) | 1 metre |
| Length (full roll) | 38 metres |
| Stretch capacity | 3–4 times original length |
| Material | Polyolefin / paraffin wax blend |
| Latex content | Latex-free |
| Permeability | Semi-permeable (allows O₂/CO₂ exchange, blocks bacteria) |
| SKU (1 m) | SH0011 |
| SKU (38 m) | SH0012 |
Complete your cultivation setup with agar plates, a pressure cooker for sterilisation, and a still air box or flow hood. Parafilm pairs directly with petri dishes and Erlenmeyer flasks — if you're doing agar work, you'll want all three on your bench.
Why Parafilm Matters for Mushroom Cultivation
Contamination kills more grows than bad genetics ever will. We've seen customers lose entire batches of agar plates to a single exposed dish left overnight. The problem isn't dramatic — it's invisible. Mould spores and bacteria float around every room in your house, and they only need a fraction of a second of exposure to land on your nutrient-rich media and start colonising.
Parafilm solves this in a way that cling film, aluminium foil, and electrical tape simply don't. It's semi-permeable — meaning oxygen and carbon dioxide pass through the film while bacterial contaminants and mould spores can't. According to research published in PMC (2023), Parafilm has been assessed for its ability to contain biological material during transport, confirming its effectiveness as a barrier against microbial contamination. A separate study published in PMC (2023) also validated Parafilm as a sterile transport matrix for biological samples, noting that sheets can be prepared under complete sterility beforehand.
That gas exchange bit is critical. If you seal a petri dish with standard cling film or tape, you create an airtight environment. Your mycelium needs to breathe. Wrap it in Parafilm instead, and you get a sealed dish that still allows fresh air in — the best of both worlds. One thing to watch: a 2025 study in PMC noted that different sealing films can alter O₂ and CO₂ concentrations inside petri dishes, so don't go wrapping 6 layers thick. A single stretched layer does the job.
How to Use Parafilm
- Cut a strip of Parafilm roughly 15–20 cm long. The film sits between a paper backing — peel the backing off before use.
- Hold the strip at both ends and stretch it gently. It'll extend to 3–4 times its original 10 cm width. You want it thin enough to be slightly translucent but not so thin it tears.
- Press the stretched film around the rim of your petri dish, Erlenmeyer flask, or jar lid. Parafilm is self-sealing — it sticks to itself when stretched and pressed, no heat or adhesive needed.
- Overlap the ends by at least 1–2 cm to create a complete seal. Smooth down any wrinkles with your thumb.
- Store your sealed dishes upside down (agar side up) in a clean, dark space at room temperature. The Parafilm seal will hold for weeks without drying out or losing grip.
- When you need to access the dish — for an agar transfer, inoculation, or inspection — simply peel the Parafilm off in one piece. It won't leave residue.
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Medical disclaimer. This content is for informational purposes only and does not constitute medical advice. Consult a qualified healthcare provider before use of any substance.