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Sterile & Lab Equipment
Unicorn 3T Grow Bags (Pack of 10)
Genuine Unicorn 3T autoclavable bags with a 0.2 micron filter patch. The standard choice for making grain spawn: filled with grain, sterilised in a pressure cooker, then inoculated with your own culture.
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Pack of 10 bags. Substrate, grain and culture sold separately.
2.5 mil polypropylene rated to 121C / 250F at 15 psi
0.2 micron type T patch keeps spores and bacteria out at the grain stage
The 3T pattern most spawn growers use, not a generic substitute
The short version
The Unicorn 3T is a side-gusseted polypropylene grow bag with a 0.2 micron filter patch. It is built to be filled with grain, sealed, and sterilised in a pressure cooker, then left to colonise into grain spawn.
The fine filter is slow on gas exchange but holds back airborne spores and bacteria well. That is why most growers reach for the 3T at the grain stage, where keeping contamination out matters most, rather than for fruiting blocks that want more air.
What it is
A sterilisation bag for grain spawn
The 3T is the spawn workhorse from Unicorn. It measures 20 by 13 by 48 cm with a side gusset, so it stands up while you fill it and folds flat when you are done. The film is 2.5 mil polypropylene, which holds up to a full pressure cooker cycle without melting.
The square patch on the front is a 0.2 micron filter, 3.8 by 3.8 cm. This is the finest filter in the Unicorn range. Air moves through it slowly, which is the point. The mycelium still gets the oxygen it needs, but mould spores and airborne bacteria are held back. Coarser bags move more air and suit fruiting blocks. The 3T is set up for the grain step, where contamination is the main risk.
| Bag size | 8 in x 5 in x 19 in, side-gusseted |
|---|---|
| Material | 2.5 mil polypropylene, autoclavable |
| Filter | 0.2 micron patch, 1.5 in x 1.5 in (Unicorn type T) |
| Rated to | 121C at 15 psi |
| Holds | About 6.5 litres by volume, roughly 2 to 3 kg of grain |
| Best for | Grain spawn production |
How to use it
Filling, sterilising, colonising
Prepare and fill
Hydrate and load your grain. Roll the top of the bag down a couple of inches and add your grain, leaving the top clear so you can fold and seal it. Wipe away any stray grain so the seal stays clean later.
Fold and load the cooker
Fold the gusseted top closed, tucking the sides in and the open top under the bag. Stand the bags upright in your pressure cooker on a trivet or rack, above the water line, with space between them for steam to move. If the cooker has no liner, keep the bags off the bare metal wall, for example with a layer of foil or paper towel, so the film does not melt against it.
Sterilise
Run the cooker at 15 psi, which holds the inside at 121C. Smaller fills need about 90 minutes once up to pressure. Some growers run 2 to 3 hours for a large dense bag packed with grain. Then let the cooker cool and fully depressurise before you open it, which can take several hours. As the bags cool they draw air back in through the filter, so cool them in your cleanest space.
Inoculate
Once cool, introduce your culture using clean technique, ideally in front of a still-air or flow hood. Bags fitted with a self-healing injection port let you inject liquid culture straight through the port without opening the bag. Shake to spread the culture, then colonise somewhere warm and dark.
Quantities and times depend on your grain, your hydration and your cooker. Treat 2 to 3 kg and a 90 minute to 3 hour cycle as a starting point and adjust to your own setup.
Handling and storage
Keep them clean and dry
Store the unused bags flat, dry and out of direct sun. They are a single-cycle consumable for hobby use, so plan on one sterilise per bag. After a cycle the film softens with heat, so handle hot bags gently and never open the cooker under pressure.
Good to know
What the 3T is not for
This is a spawn-stage bag, not a wide-open fruiting bag. Its fine 0.2 micron filter is deliberately slow on gas exchange, so for bulk fruiting blocks that want more air, growers usually move to a coarser filter bag. The 3T is also not a substitute for proper sterile technique. The bag keeps contaminants out, but only if you keep your work area and your hands clean while it is open.
Common questions
Frequently asked
It blocks airborne spores and bacteria while still letting the mycelium exchange some air. It is the finest filter Unicorn make, which is why it suits the grain stage. The trade-off is slower gas exchange, so it is not the choice for fruiting blocks.
Yes. They are rated for 121C at 15 psi, the standard pressure cooker setting. Stand them upright on a rack above the water and keep them off the bare metal wall so they do not melt.
The bag holds about 6.5 litres by volume, which is roughly 2 to 3 kg of hydrated grain. Leave the top clear so you can fold and seal it.
Smaller fills need about 90 minutes once up to pressure. Some growers run 2 to 3 hours for a large dense bag packed with grain. Then let it cool fully before opening.
The base 3T does not. A separate self-healing injection-port version lets you inject liquid culture without opening the bag, and stick-on ports can be added to plain bags. Check the variant you order.
Treat them as single-cycle. The film softens with heat and the filter and seal are made for one run.
Use them for legal gourmet cultivation and for spores or cultures kept for microscopy. We do not supply anything for unlawful use.
Sources
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Sold as sterile cultivation equipment for legal gourmet mushroom growing and for spores and cultures held for microscopy. We make no health or medical claims.
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