Adherable Lid Filters 50-Pack (Microppose)

Microppose Adherable Lid Filters 50-Pack: 0.3-Micron Contamination Defence for Mushroom Growers

The Microppose Adherable Lid Filter is a self-adhesive, 0.3-micron filter patch that blocks bacterial and fungal contaminants from entering your growing containers while still allowing gas exchange. Stick one over a hole in your jar lid, spawn bag, or monotub and your mycelium gets the fresh air it needs without the uninvited guests. Fifty filters per pack — enough to kit out a serious batch run or keep a hobbyist stocked for months.

Why 0.3-Micron Lid Filters Are Critical for Mushroom Cultivation

Contamination is the single biggest reason mushroom grows fail — and it usually happens through the air holes you drilled yourself. Trichoderma, Neurospora crassa (the bright orange bread mould), Rhizopus stolonifer, Bacillus species — they're all floating around your workspace on invisible spores. One lands inside your jar and the whole thing is done. We've seen growers lose ten jars in a row because they used micropore tape that peeled back after a single sterilisation cycle.

These Microppose filters solve the problem properly. The 0.3-micron pore size is small enough to physically block bacterial spores (most are 0.5-5 microns) and fungal contaminants (typically 2-50 microns), while still allowing oxygen and CO2 to pass through. That's the balance you need: your mycelium breathes, contaminants don't get in. The oleophobic and hydrophobic material means moisture and oils won't clog the filter either, so it keeps working through the entire colonisation and fruiting cycle.

The honest limitation? These are single-use. Once you've pressure-cooked a jar or autoclaved your grain, the adhesive has done its job and you shouldn't try to peel and reapply. At 50 per pack, though, the cost per jar is minimal — and that's a fraction of what you'd lose replacing a contaminated batch of grain spawn.

Specifications

What Makes These Better Than Micropore Tape

Most growers start with micropore tape. It's cheap, it's available at any pharmacy, and it works — sort of. The problem is that micropore tape peels. Condensation from sterilisation loosens the adhesive, and once there's a gap between the tape and the lid, contaminants walk right in. We've had customers tell us they double- and triple-layered micropore tape only to find green mould in their jars two weeks later.

Microppose filters use 3M adhesive that's specifically designed to hold under heat and moisture. Once it's stuck, it stays stuck. The filter material itself is also a step up — the 0.3-micron rating is tighter than standard micropore tape (which typically sits around 0.5 microns), and the oleophobic coating prevents the filter from becoming saturated and losing airflow. It's the difference between a bodge job and a proper solution. If you're running more than a couple of jars, the upgrade pays for itself the first time you don't lose a batch.

How to Apply Microppose Adherable Lid Filters

1. Drill or punch a hole in your jar lid, tub lid, or growing container. A 20-25mm hole works well — large enough for adequate gas exchange but not so large the filter can't cover it with overlap on all sides.
2. Clean the surface around the hole with isopropyl alcohol (70% IPA). The adhesive bonds best to clean, dry, grease-free surfaces. Let it dry completely.
3. Peel the backing off one Microppose filter and press it firmly over the hole, smooth side out. Make sure the adhesive makes full contact around the entire perimeter — no air gaps, no lifted edges.
4. If you're using these on grain jars for pressure cooking, apply the filter before sterilisation. The 3M adhesive and filter material are rated to withstand autoclave temperatures (121°C at 15 PSI).
5. After sterilisation, allow jars to cool to room temperature before inoculation. If you're using Microppose Injection Ports, inoculate through the port without ever opening the lid.
6. Once colonisation is complete and you move to fruiting conditions, the same filter continues to provide gas exchange. No need to swap or modify.

From Our Counter: When Filters Actually Matter Most

There's a misconception that contamination mostly happens during inoculation. It can, sure — but the real danger zone is the first 3-5 days after inoculation, when your grain or substrate is warm, moist, and nutritious but the mycelium hasn't colonised enough to defend itself. During that window, any gap in your filter is an open invitation. We've watched growers obsess over their still air box technique and then stack their jars on a shelf with dodgy tape. The filter is your 24/7 guard — it matters more than any single moment of sterile technique.

One thing to watch: don't stack jars so tightly that the filters are pressed against each other or against a shelf surface. The filter needs a small amount of airspace above it to allow gas exchange. A wire rack or a bit of spacing between jars is all you need.

Contaminants These Filters Block

Frequently Asked Questions

Last updated: April 2026