Cultivation Guide

How to make jars with substrate for mushroom spawn

STEP 4. How to prepare Spawn Jars and Spawn Bags by your own and save money. Spawn Jars types: autoclavable polypropylene and glass jars. Components for making Inoculation Port and Air Filter. Recommended volume for Spawn Jars and Spawn Bags

STEP 4. Day 2. How to prepare spawn jars and spawn bags

On the previous step you've already cooked the substrate for magic mushrooms. Now you need to prepare spawn jars or spawn bags in order to proceed with sterilisation process.

For this purpose growers use different kind of jars, containers or spawn bags for substrate with inoculation port and breathable air filter. Let's figure out different options!

What is inoculation port and air filter?

Each container, either a polypropylene heat-resistant bag or any jar with lid should be equipped with an inoculation port and a breathable air filter.

Inoculation port (aka injection port) — is an entry point for a syringe needle containing the liquid spore solution or liquid culture to inoculate the sterile substrate. It must be protected agains any competing microorganisms contamination through it. Bactericidal breathable patch, butyl rubber self-healing injection ports (aka bottle stoppers) or heat-resistant RTV-silicone sealant is used for this purpose.

Breathable air filter — is a filter that provides gas exchange during the colonisation period. It must be protected by bactericidal layer to prevent any competing microorganisms from entering through it. Bactericidal breathing patch, Luer lock syringe filters, and synthetic filter disks are used for this purpose.

Mushroom cultivators practice in different ways. Someone makes two holes in the lid: one for injection port and one for filter. Someone makes several ports for inoculation and several filters for air exchange.

It is cheap and easy to make by your own or you can buy ready to use jars with lid components for mushroom spawn.

Jars, lids and lid components for Spawn Jars

There is a huge variety of materials that can make growing process easier. Let's take a look at the different options and alternatives.

❇️ Mason jars for spawn

Glass Mason jars with metal lids. Each lid consist of two parts: a replaceable lid disc with a rubber seal around the rim and threaded ring

Mason jar for substrate. Spawn jars. Psilocybin mushrooms cultivation
Mason jar. Lid with injection port (butyl rubber) and air filter (micropore)

Glass Mason jars with heat-resistant autoclavable plastic lids. You can prepare your own or buy ready-made lids. Inoculation port — butyl rubber injection port. Filter — laboratory funnel filter or substitute with a patch.

Glass spawn jars with heat resistant polypropylene lids
Glass spawn jars with heat-resistant polypropylene lids

🔴 In fact you can use any glass jars for canning

Shroomok's Choice on Amazon:

Ball Wide Mouth Mason Jars with Lids & Bands | 16-oz | 2-Pack - $13.78

Ball Wide Mouth Mason Jars with Lids & Bands | 24 oz | 2-Pack - $14.04

Ball Wide Mouth Mason Jars with Lids & Bands | 16-oz | 6-Pack - $18.99

Ball Wide Mouth Mason Jars with Lids & Bands | 32 oz | 12-Pack - $31.04

❇️ Lid components for spawn jars

Each lid should be equipped with inoculation port (butyl rubber injection port) and a air filter (synthetic patch or micropore nylon lab filter).

Inoculation port - butyl rubber injection port, air filter - Luer lock syringe filter
Inoculation port - butyl rubber injection port, air filter - Luer lock syringe filter

Butyl rubber self-healing bottle stoppers is a great option for inoculation port.

Luer-lock syringe filter is a great option for air filter.

These components can be installed in any kind of lids (polypropylene or metal), polypropylene containers or spawn bags. All components are autoclavable and reusable!

❗️Use heat resistant RTV silicone to instal, glue and seal lid components!

Shroomok Choice on Amazon

Plastic (5PP) or Stainless steel autoclavable lids:

Plastic Regular Mason Jar Lids, 8 Pack - $9.99

Plastic Mason Jar Lids, Wide & Regular, 24 Pack $14.99

Stainless Steel Mason Jar Lids and Rings, Wide & Regular, 48 Pack - $16.96

Air filters for lids:

Synthetic Filter Disc for Air filter - 64/128/256 pcs. - $7.99

Syringe Filters PTFE Hydrophobic - 25 pcs. - $13.99

Inoculation port for lids:

Mushrooms Self Healing Injection Ports - 20mm, 100 pcs. - $10.99

2-in-1: Synthetic Filter Paper Stickers 64 pcs & 100 pcs Injection Ports - $9.99

To glue and seal lid components:

High Temperature RTV Silicone and Sealant - Red - 3 oz. - $8.29

Ready to use Jars with Lids + air filter + inoculation port:

Wide Mouth Mason Jar Plastic Lid + Syringe Filter + Self Healing Injection Ports - 3 pcs - $14.99

3-in-1: Ready to use Mason Jar Lid, Syringe Filter & Self Healing Injection Ports - 6 pcs - $22.99

❇️ Heat-resistant polypropylene spawn bags

You can make by your own or use ready-made bags with inoculation port and air filter.

Spawn bags for mushrooms cultivation
Spawn bags for mushrooms cultivation
Spawn bag with injection port and air filter
Spawn bag with injection port and air filter

Shroomok's Choice on Amazon:

Small-Medium Mushroom Culture Bag with Air Filter- 10 pcs. - $6.59

Middle Mushroom Spawn Bags with Filter -10/20/50/100 pcs. - $9.99

Large Mushroom Grow Bags with Gas Filter - 10/25/100 pcs. - $11.99

3-in-1: Autoclavable Grow Bag + Injection Port + CO2 Filter - 10 pcs - $28.49

❇️ Glass canning jars for Spawn Jars
Glass jars for substrate with metal lids. Spawn jars for psilocybin mushrooms cultivation
Glass jars for substrate with metal lids. Spawn jars for psilocybin mushrooms cultivation
❇️ Heat-resistant polypropylene autoclavable jars for Spawn Jars
Heat-resistant polypropylene jars for substrate
Heat-resistant polypropylene jars for substrate. Lids with one hole for injection port and filter covered with bactericidal patch
Polypropylene jars for spawn
Polypropylene jars for spawn

How to identify heat-resistant autoclavable plastic for spawn jar?

Look for 5PP and "for food" labels

How to identify heat-resistant polypropylene jars for spawn
How to identify heat-resistant polypropylene jars for spawn. PP symbol

Shroomok's Choice on Amazon:

Polypropylene Jars with Lid for Grain Spawn or LC - 12/24/50-Pack 8/16/32 oz. - $8.99

Polypropylene Jars for Grain Spawn & LC - 24 oz. (16 oz, 32 oz available) - 9 Sets - $9.97

Autoclavable Reusable Polypropylene Jars with CO2 Filter in the Lid |17-oz | - 6 pcs - $19.99

How to make injection port with RTV silicone

You can use heat-resistant red RTV silicone for DIY self-healing injection port.

Red RTV silicone sealant as injection port for spawn jar
Red RTV silicone sealant as injection port for spawn jar
Heat-resistant rtv silicone sealant as injection port
Heat-resistant rtv silicone sealant as injection port

Shroomok's Choice on Amazon:

High Temperature RTV Silicone Gasket Maker and Sealant - Red - 3 oz. - $8.29

What to use is up to you!

DIY spawn jars

To make DIY jars and lids for substrate you need:

  1. Jars with lids (volume, types of jars and lids we are going to discuss below).
  2. Screwdriver/nail/awl/drill with a diameter of 5-10 mm.
  3. Bactericidal breathing patch — 1-2 per lid.
  4. Heat-resistant rtv silicone sealant — optional.
What volume for spawn jars is needed

Any jar that fits your pressure cooker (autoclave or multicooker) from 250 ml to 1 liter. We use 500 ml and 700 ml jars. For us these are the optimal volumes. The shape of the jars does not matter.

Jars for substrate
Polypropylene jars with polypropylene lids or glass jars with metal lids

🔴 Note: The shape of the jars is important for PF-tek growing. Use cylindrical or conic jars without narrow neck (neck should be wider than the bottom), so that you can take out the mushroom cake safe and sound or you can open it up with some extreme demonstarted in the video below:

Jars more than 1 liter are not recommended. Why?

  • First, the jar may not fit in the pressure cooker (multicooker).
  • Secondly, a large volume will require more time to colonize the substrate. Accordingly, more risk for souring and contamination, which can take over the substrate faster than the mycelium of psilocybin mushrooms.
  • Third, it is better to share the risks and make more jars of smaller volume. So that, increase the chances of future mushroom survival.
  • With more jars you can experiment and try different methods. Mycelium in each jar will be genetically unique and there is an opportunity to select the best one.
What kind of jars are needed

We use glass screw jars with metal twist-off lids (withstand temperature over +160°C or 320°F) or Mason jars.

Glass screw jars for substrate with metal twist-off lids
Glass screw jars with metal twist-off lids

A

nd heat-resistant polypropylene jars with polypropylene lids (withstand temperature up to +140°C or 284°F).

Heat-resistant polypropylene jars for substrate
Heat-resistant polypropylene jars for substrate


Pros of glass jars:

  • Availability.
  • Easily withstand higher temperatures than polypropylene jars. This point is especially important if your pressure cooker doesn't allow you to set a specific temperature.

Cons of glass jars:

  • The jar can crack or break during the sterilization process. You can't use such jar and substrate in it for inoculation.
  • It is more difficult to shake the substrate that has covered by mycelium.

Pros of polypropylene jars:

  • Flexible and elastic (it will be easier to shake the substrate with mycelium in such jars)
  • Don't crack or break during sterilization, as it can happen with glass ones.

Cons of polypropylene jars::

  • Under the influence of temperature changes, the lid can open, then we can't use such substrate for inoculation. Make sure that the lid is tightly closed before and after sterilization.


In fact, we had no problem either with polypropylene (500 ml) or glass (700 ml) jars. The choice is up to you.

Step-by-step spawn jars and lids preparation

1️⃣ Wash all jars and lids. You can use a dish detergent.

Wash all jars for substrate and lids to it. Jars and lids preparation for growing psilocybin mushrooms
Wash all jars for substrate and lids to it


2️⃣ Make only one hole in each lid for the injection port and air filter. Diameter about 5-10 mm. Polypropylene lids can be burned through with a red-hot nail/awl or a screwdriver.

Or you can use hot gun.

Polypropylene jars for mushroom grain spawn. How to make air filter and inoculation port with hot gun
Polypropylene jars for mushroom grain spawn. How to make air filter and inoculation port with hot gun
Make inoculation port and filter in the lid. Jars and lids preparation for growing psilocybin mushrooms
Make inoculation port and filter in the lid

Tape inoculation port with a breathing bactericidal patch outside (omnipore or micropore tape). Try to stick the patch so that the breathing dots on the patch show you where the center of the inoculation port is. This will make inoculation more convenient.

Inoculation port with filter in the lid. Preparation jars for substrate and lids to it
Inoculation port with filter in the lid

Shroomok's Choice on Amazon:

3M Micropore Tape 1530-1 (2 rolls) 1 x 10 yards - $4.50

Micropore Surgical Tape - 3m - 2" x 10 YD - 6 rolls - $8.15

Box of Flexible breathable bandages - 50 pcs. - $11.99


🔴For metal lids you can use a drill or punched with a nail/awl/screwdriver.

Make one hole in metal lid for inoculation port and filter
Make one hole in metal lid for inoculation port and filter. Use drill or screwdriver
Diameter of injection port and air filter is 5-10 mm
Diameter of injection port and air filter is 5-10 mm

🔴 Important: if you make a hole in the metal lid, it is necessary to bend the metal pieces on the back side and seal this place with a breathing bactericidal patch both - inside and outside! It is necessary, because water drops with rust from the lid accumulated there and contamination can easy get in. For polypropylene jars only one breathing bactericidal patch (outside) is needed

Metal lid with inoculation port and filter (inside view)
Metal lid with inoculation port and filter (inside view)
Metal lid with inoculation port and filter (outside view)
Metal lid with inoculation port and filter (outside view)


4️⃣ Inoculation port can be made with heat-resistant RTV silicone sealant. This is a great alternative to butyl rubber bottle stoppers.

Red RTV silicone sealant as injection port for spawn jar
Red RTV silicone sealant as injection port for spawn jar
rtv silicone injection port
rtv silicone injection port


Fill the hole for the inoculation port with heat-resistant silicone sealant (rtv silicone) on both sides.

Injection port with rtv silocone
Fill inoculation port with rtv silocone on both sides


The silicone that hasn't yet solidified should be pressed lightly with a napkin inside and outside of the lid. So that it takes the shape of a tablet or wax seal. Wait for the sealant to completely solidify.

rtv silicone inoculation port
Press gently with a napkin inside and outside

Don't forget to make another separate hole in such lids for air filter and cover it with patch or filter disc.


Jars for mushroom spawn are ready!

Move on the next stage — STEP 5. Day 2. Substrate sterilization

  1. Cultivation Guide
  2. DIY Spawn jars & Spawn bags