Custom jar lids

Making Jar Management Easy

The picture on the left is a jar of mycelium. We want to protect it from contamination but at the same time not deprive it of air—that same air that contains contamination.

In this blog, we are going to share our way of building our custom jar lids to make day-to-day jar management easy, and provide protection against contamination. When the hobbyist gets a pack of jars, the lids are plain and there are no holes. Since we are dealing with mycelium, and mycelium is alive, then at some degree it will require air exchange.

There are many types of materials that can be used to accomplish this, but we are going to stay on the cheap side to accomplish this. However, we have to keep in mind that whatever we use has to be reliable. A modified lid that no longer seals will probably mean the end of our mycelium, so we need to build cheap, yet still reliable.

Liquid culture jars, grain jars and agar jars all require custom made lid.

Liquid culture jars require a lid with an injection port and a air exchange port. The same goes for grain jars that require an injection port to inject liquid culture into the grain and an air exchange port. Finally, agar jars that just require an air exchange port.

So, we end up needing two types of custom lids:

  • injection port + air exchange port
  • air exchange port only

And here is the materials required and how we build our custom lids:

  • micro pore tape
  • small drill bit
  • injection port
  • high temperature RTV which is a car gasket maker 

Making holes in a lid is straightforward, so we are not going to explain how to make a hole, but basically we need two type of holes: one small hole for air exchange and one larger hole for the injection rubber.

The injection rubber port has to be tight enough to hold the rubber in place, so make the hole smaller than the rubber. Before pushing the rubber in the hole on the lid we put RTV around the hole. In the following pictures, you can see the end result.

The first image on top is for making agar jars where the only port needed is for air exchange. The three next pictures are for grain jars and for liquid culture jars; for both, we need air exchange but also an injection port, so we can use a syringe to inoculate.

A single lid built this way can be used multiple times, but every time we sterilize, we must change the micro pore tape. Always use two layers of tape. We have been sterilizing grains, agar and liquid culture with our lids with no problem for months.

Keep in mind that the injection ports need to be replaced when there are too many needle holes on them, otherwise they may not offer proper seal, which could result in live culture or grain contamination.

When applying RTV, be generous to properly create a seal between the lid and the injection port.

We understand that for some people, building custom lids can be annoying, and that is why we have them for sell in our shop section, which includes a roll of micropore tape.

Please see our other blogs covering more specific subjects about the fun world of growing mushrooms.

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