How to make self-healing injection port lids for grain spawn and liquid cultures!

Creating self-sealing injection port (SSIP) lids for grain spawn jars and liquid culture jars is an integral part of mushroom cultivation. These lids allow for sterile inoculation of the jars without exposing the contents to contaminants in the open air. Here's a detailed step-by-step guide:

Materials Needed:

1. Wide-mouth canning jars with metal lids (size depends on your needs).
2. High-temperature silicone sealant (e.g., RTV silicone).
3. Synthetic filter discs (SFD) or Micropore tape.
4. Drill with 1/4-inch and 3/8-inch drill bits (or sizes to match your injection ports and filters).
5. Rubbing alcohol and paper towels.
6. Optional: Gloves.


1. Cleaning: Clean your jar lids thoroughly with warm soapy water, rinse, and dry. This will help the silicone adhere properly. You may also wipe them down with rubbing alcohol.

2. Drilling the Injection Port: Choose a spot on your lid for the injection port. This will usually be towards one side of the lid, not in the center. Carefully use your drill with the 1/4-inch bit to drill a hole through the lid at the chosen spot. Clean up any metal shavings and wipe the lid down again with rubbing alcohol.

3. Drilling the Gas Exchange Filter Hole: Now, choose a spot for the gas exchange filter. This should be on the opposite side of the lid from the injection port. Use your drill with the 3/8-inch bit to drill a hole for the gas exchange filter. Again, clean up any metal shavings and wipe down the lid with rubbing alcohol.

4. Applying the Silicone: Now, take your high-temperature silicone sealant and apply a good-sized blob over the injection port hole on the top side of the lid. It should be large enough to form a nice seal, but not so large that it will interfere with screwing the band onto the jar. Then, apply a similar amount of silicone on the underside of the lid over the same hole. This double layer creates the self-sealing injection port.

5. Setting the Silicone: Allow the silicone to cure according to the manufacturer's instructions. This is usually 24 hours, but can be longer. Do not touch or disturb the silicone during this time.

6. Applying the Filter: Once the silicone is fully cured, you can add the gas exchange filter. If you're using a synthetic filter disc, you can secure it over the gas exchange hole with a small ring of silicone and allow it to cure. If you're using Micropore tape, you can cover the hole with a couple of layers of tape.

7. Final Clean: Once everything is dry and fully cured, give the lids one final wipe down with rubbing alcohol before use.

And there you have it! You've made your own injection port lids for mushroom cultivation.

Remember, always use caution when drilling metal and working with silicone sealants. Always work in a well-ventilated area, away from open flames, and protect your eyes, hands, and work surfaces.
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