Paddling: Making a Silicone Injection Port

When it comes to growing your own mushrooms, there are few things more frustrating than contamination from a lack of sterility, especially after all the effort, patience and time you’ve spent on your grow. It’s a recognizable situation for many novice psychonauts; even after all the effort to create a spore syringe in a sterile environment, things can quickly go downhill if the inoculation is not done with care. One way people try to avoid this is to employ an “inoculation jar” – a glass jar filled with your growing medium. What makes these jars so special is the lid, which is manually adjusted to allow for the perfect inoculation.


What’s the point of these ports? Well, assuming you’ve been sterile up until now when dealing with your spore syringe and growth medium, a silicone injection port and the exchange of air ensures that the culture remains sterile while the mycelium persists – a particularly vulnerable stage of the process. This is because no contaminants can enter during or after inoculation, while the jar can still breathe. To create these ports, you need to modify the lid of the jar. First, we will start with the injection port.


For this you will need:

  • A glass jar with a lid
  • A drill with a 6.5 mm drill bit
  • RTV silicone sealant
  • Paper


  1. The first thing to do is to drill two holes in the lid. It is best to place the holes both just off center, leaving enough space between them.
  2. Cut a few squares of paper large enough to cover one hole. Note: Although two holes are drilled, one hole will be used for the injection port. The other hole will be used later for the air filter port. Thus, the steps below should be performed for one hole.
  3. Make sure the lid is clean and sterilized, take the silicone sealant and make an outline around one of the holes at the bottom. Once done, fill the rest of the circle with sealant. Making a circle around the outside first will make filling the hole easier.
  4. Repeat on the other side of the lid.
  5. Take the square papers and place them accurately on either side of the lid, on the silicone. Gently press both sides down so that it is flattened.
  6. Set the lid aside to dry. Make sure the silicone doesn’t come into contact with anything but the paper, or it will stick when it dries.
  7. Once the silicone is dry you can carefully peel off the paper. This will create a nice, flat silicone injection port. This will cure itself after use, so nothing but the syringe will go through it!


Now that you have a safe way to inoculate your growing medium with spores, it’s time to make an air filter port, allowing the pot to breathe without risk of contamination. To do this you will need:

  • Cotton fiber aquarium filter
  • Pliers


  1. You’ve already drilled a second hole in the lid. This will be used for the air filter port.
  2. Take a strip of your aquarium filter material and roll it into a small roll the size of the hole.
  3. Then fold it in half and cover the top with additional material. This will provide an uncompromising and smooth layer to work with.
  4. Trim the extra material so that you are left with the small roll, then from the bottom of the lid work the covered center fold through the hole so that the roll extends about 1 cm above the lid. This is very tricky, and you may need to use pliers to pull the roll through the hole. You want to keep it as tight and windproof as possible.
  5. Cut away the excess material at the bottom. You now have an air filter port! The filter material will allow fresh air to pass through and catch any particles or materials that may cause contamination.

There you have it, a lid complete with an injection and air filter port allowing your mycelium to grow without nasty contaminants. This method can also be used to add extra security to inoculation bags; with some silicone and some gauze over the injection tip, the inoculation contamination remains free! Some bags already have a built-in injection port themselves. That’s worry-free inoculation! Check out this video in case the above step-by-step plan is not entirely clear.