How to make mushroom grain jar lids

When growing mushrooms using grain jars, the lid setup plays a crucial role in maintaining sterility while allowing for proper gas exchange. Standard jar lids can be modified or replaced with specialized lids designed for mushroom cultivation.

Injection Port (Self-Healing Port) – A small rubber or silicone port that allows for clean, sterile injections of spore syringes or liquid culture without exposing the jar to contaminants.
Gas Exchange Filter (Polyfill, Tyvek, or Synthetic Filter Disks) – Since mycelium needs oxygen, lids include a breathable filter to allow for gas exchange while preventing contaminants like mold and bacteria from entering. I like to use cloth surgical tape. Two pieces. Cover your lids with foil before you pressure cook.
Tight Seal (Metal or Plastic Lids) – Lids must seal securely to maintain sterility but still allow for proper air exchange through the filter.

DIY Modified Lids – Many growers modify standard metal mason jar lids by drilling a hole for an injection port and covering another hole with micropore tape, Tyvek, or polyfill for airflow. This is what I am doing in the video above. These lids work great and are usable over and over. You may need to reapply the silicon bead once in awhile.
Pre-Made Filtered Lids – These ready-to-use plastic or metal lids come with built-in injection ports and high-efficiency filters to maximize sterility and ease of use. I have honestly never purchased these. They were so simple to make I didn’t bother. I could see buying them if you had hundreds to make.

Prevents Contamination – The combination of a self-healing injection port and a filter reduces the risk of bacteria or mold entering the jar.
Allows Mycelium to Breathe – Without proper gas exchange, mycelium can stall or grow weak.
Supports Faster Colonization – Well-ventilated jars allow for steady mycelium growth without excessive moisture buildup.

There are a bunch of different lid manufacturers our there. Here is one I found on Amazon.

As I said previously, I don’t buy ready made lids, but these look pretty legit!