Modifying Mason Jar Lids

Part 1 : Unit 3 : Modifying Mason Jar Lids for Mushroom Cultivation

Mason jars play an important role in mushroom cultivation, for sterilizing grain, substrate, or Liquid Culture. Making some slight modifications to the jar lids is well worth the effort, and can save you a whole bunch of headaches down the road. What do these modifications include? It’s actually rather simple: You’ll make two holes in the plastic lid, one for the injection port, and the other for the filter sticker. These additions allow you to insert or extract sterile liquid culture from the jars without having to open them and expose them to possible contamination. Once you’ve got all the required tools, it’s a 10 minute procedure. Why is this worthwhile doing? We’re happy you asked. Incorporating liquid cultures in your growing journey adds a whole new dimension to your cultivation abilities. From faster colonization times to storage of special genetics, liquid cultures can improve the quality and cleanliness of your work. How do these modifications work? By allowing clean and sterile access into the jar through the injection port, and also allowing clean air flow into the jar through the filter sticker – you’ve got a sterile means of inoculating things, especially if we use sterile syringes and needles. So, without further ado we will begin our path to mycelial independence!
Modified mason jar lids
Modified Mason Jar Lids

Modifying Jar Lids for Mushroom Cultivation

Video Tutorial : Modifying Mason Jar Lids for Mushroom Cultivation

The video markers above 👆🏼correspond to the the various Steps in this Unit. Click on them to skip to a Step.

Step 1 : Drill the Larger Hole for the Injection Port

You want to drill 2 holes in the lid – a larger hole (7/16″) for the injection port, and a smaller hole for the air filter. It is important not to drill the holes too close to the edge of the lid, since this will make it hard or impossible for you to apply the filter sticker and the injection port, but you also need to have enough space between the two holes, as shown in the diagram on the right. Slowly engage the drill and push the drill bit through the lid to the 7/16″ mark on the drill bit. This leaves just enough space for the injection port to be pushed in. Clean any plastic residue from the lid and make sure there are no sharp plastic pieces hanging off the drilled hole. You want to have clean cut holes, so that the injection port will be flush with the lid when applied. Very carefully proceed to enlarge the hole until you get to the 7/16″ mark on the step drill bit.
Mason jar lid hole position

Step 2 : Drill the Smaller Hole for the Air Filter

Now drill the smaller hole – about 1/4″ should be big enough. Again, make sure the hole is clean cut, with nothing to interfere with the adhesive of the filter. Switching drilling sides can help give you clean cut results, as shown in the video.

Step 3 : Insert the Injection Port into the Larger Hole

Push the injection port through the larger hole, with the flat round part on top. Because it’s a tight fit, pushing it through usually won’t be enough. You will need to pull and tug at the injection port from the other side to help it go all the the way through. Make sure the injection port is flat and flush with the top of the lid, and the bottom of the injection port is round and unpinched.

Step 4 : Apply the Air Filter Sticker Patch on the Smaller Hole

Alcohol-wipe the area around the smaller hole on the inside of the lid, and then dry it with a towel so that the sticker sticks well. Apply the filter sticker onto the smaller hole from the underside of the lid, making sure it is centered. Apply pressure on the whole sticker to make sure it sticks well. This is important as this lid will be exposed to high pressures and temperatures.

Place the silicone gasket around the inside of the jar lid. You always want to make sure the gasket ring is in place when closing a jar.

That’s it! Continue preparing all the lids you need, one by one. Each one will require your full attention, and don’t cut corners. Once that’s done, give yourself a pat on the back – you’ve completed a quick but very important step!

Troubleshooting : I made the injection port hole too big!

It takes some time to get a feel for the drill and the hole size you’re making. If you go past the 7/16″ mark and the hole isn’t a tight fit, you can use some “High Temperature Silicone / Gasket Sealant” around the injection port hole, and seat the injection port in the hole. The sealant should provide an airtight seal after 24 or 48 hours of hardening.

Next Unit: Building a Still Air Box (SAB) and a Monotub. In the next Unit you will learn how to build a SAB and a Monotub, both crucial tools in your mushroom cultivation journey.

2 Responses

    1. Yes, this process could be replaced by span bags, and as a more seasoned grower, spawn bags are my favorite method to go with. Spawn bags do require some more hardware and can get quite expensive, especially if using biodegradable materials and having them come with injection ports. Without injection ports, I believe spawn bags are much more prone to contamination when you’re beginning your growing journey.

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