Grow mushrooms the EZ way.

How To Make Mushroom Jar Lids.

Mushroom Jar Lid

Welcome to this tutorial on how to make mushroom jar lids!

In this guide, we will show you how to create your own mushroom jar lids using either low cost methods such as micropore tape or professional style lids using an air port.  

Regardless of which method you choose, the process is easy and can be done at home with a few simple materials.

The purpose of grain spawn or liquid culture lids is to provide a gas exchange barrier for your mycelium whilst blocking out unwanted contaminants and their spores. 

In this tutorial, we will show you how to make your own mushroom jar lids for grain spawn, liquid culture or agar. 

These lids should give you the ability to easily and effectively create a sterile environment for your mycelium to grow.

There is a plethora of methods to making mushroom jar lids, in this post I will cover the following:

  • Injection Port and Air Pot lids.
  • Micropore tape Lids.
  • Stiff Felt Lids.

Making Injection Port And Air-Port Mushroom Lids.

This setup is the most professional style of the lid you can make.

It uses a small airport for gas exchange and a self healing injection site. 

This type of lid makes creating sterile grain spawn and liquid culture much easier.

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  • Lower contamination rate.
  • Precise air exchange.
  • Self healing injections.


  • Can be messy to set up.
  • Makes putting foil on the top of your jars more difficult.

Materials Needed


RTV Silicone.

Sharp Object.

Air-port and injection port.


I drill holes in the lid that's large enough to fit the injection port and air port.

Put a smaller hole in the centre (this is where the air exchange port will go) and place the injection port nearer the edge of the lid.

This makes it easier to extract liquid culture or inject down the side of grain spawn.

The hole doesn't have to be the perfect size or shape, as I will seal it with RTV later.

I  push the thin side of the airport through the hole to ensure there's a good fit.

I apply RTV silicone generously to the underside of the air port, so there's a thick amount on the whole underside (the thinner side should be face down).

Air port underside covered in RTV

I push the injection port through the hole I created and apply pressure for around 20 seconds.

Airport lid

Next, I do the same for the injection port.

I push the injection port through the hole to ensure a good fit.

I apply a generous amount of RTV to the underside of the injection port.

Injection port Lid

I push the injection port through the hole I created and apply pressure for around 20 seconds.

Mushroom lid creation

Finally, l set the jar aside and leave it to cure for 24 hours before use. This will allow the RTV silicone to cure before exposing it to heat.

Alternatively, it is possible to create your own injection port using only RTV silicone. 

To do this you just fill the hole you’ve made with RTV silicone then inject through the silicone when you are using your lids.

Making Stiff Felt Mushroom Lids.

It is possible to use stiffened felt to create the gas exchange filter over the hole in your lids.

I have had lots of success with these lids before I moved onto air ports.


  • Cheap.
  • Simple.
  • Effective.
  • Long term setup.


  • Felt may wick moisture into/out of jars.
  • Can be fiddly/messy to set up.
  • Can't inject through the felt.

Materials Needed


RTV Silicone.

Stiffened Felt.

Sharp Object.


Create a 1-2mm hole in the lid of the jars.

Cut out a piece of stiffened felt which will cover this hole and place it over the top of the hole.

Seal the edges of the stiffened felt with RTV silicone by massaging it down against the lids and the stiffened felt.

Its best to do this with some wet tissue on your finger or a piece of scrap plastic

You want to make sure the edges are sealed down to the jar and there are no air pockets or areas not covered.

Alternatively you can attach the stiffened felt to the bottom of the lid.

Making Micropore Tape Lids.

This is the most basic lid often used in PF-tek. It is a no thrills lid which uses micropore tape which you inject through and which provides the barrier for the mycelium. 

After each injection you should place another piece of tape over the hole created. Checkout how to use liquid culture for an example of this.


  • Cheap.
  • Simple.
  • Effective.


  • Results in lots of layers of tape after lots of use.
  • Tape adhesive can get stuck to jars
  • Tape can harbor contaminants if wet.

Materials Needed


Micropore tape.

Sharp object.


Collect all your items.

Create a hole in the lid of your jar using the sharp object you want for the whole to be around 1-2mm in diameter.

Place two strips of micropore tape over the hole.

Covering grain jar hole with micropore tape

You can also mix up the techniques as show below.

For PF-tek i dont like to use a air exchange port as the vermiculite at the top of the jar may block the air port. So instead I use injection ports with micropore tape.

Mushroom jar lids


Hopefully I have given you some ideas on how to create mushroom jar lids for grain spawn and liquid culture jars.

There are plenty of options out there but it is best to try out different techniques and see what provides you with the best results for you. 

If all else fails you can buy premade mushroom lids on amazon as seen below.