Injection ports allow the safe injection of a liquid culture or spores into the sterile environment of grain or substrate. The needle pierces the port, usually rubber or silicone, tearing a channel through it.
The needle keeps the channel open and creates a perfect seal around itself. Once finished injecting, the needle is withdrawn, and the elastic nature of the material means the channel closes up as it withdraws. This is why injection ports are known as self-healing. There is a life on the injection ports, but this depends on the needle gauge.
Grow bags with injection ports are expensive, they average around 4 – 6 times the cost of regular bags for that little bit of rubber.
Injection ports are commonly found on the lids of ‘airport jars’, you can read an article on how to build them here. Putting injection ports onto bags is much more of a head scratcher. Since you don’t have a solid surface to bond to, the ports must be flexible enough to move with the bag whilst maintaining a grip on thin plastic without coming loose and exposing sterile substrate or grain to an unsterile environment. This is often a bigger issue with bags, as they move around they can create positive and negative pressure through the smallest holes, potentially sucking contamination in.
Unless the mycelium in the liquid culture is incredibly thick and old, you can draw and inject it through a 22gauge needle with very few issues, this is aided by using a stirrer bar to break up the mycelium before you draw and inject. The gauge of needle has a direct bearing on the life of your injection ports!
The easiest method is to put a strip of micropore tape on the bag and then inject through it, then sealing it after with another layer of tape. This tape is added after sterilising btw. This method works well but isn’t always reliable especially if the micropore tape gets wet it can work itself lose.
A common method is to cut a small hole in the bag about ¼ to 1/3rd of the way up. Then using some RTV silicone you apply a dab to both sides. Once this sets up it creates a seal. This method isn’t the best as silicone doesn’t grip very well on shiney surfaces. Lightly keying the bag with 600 grit sandpaper gives the silicone more to grip on. Incidentally, you don’t need to use RTV, most silicone has a high enough tolerance to survive sterilising. There is a great video by WillyMyco making this bag, check it out here.
This method is at risk from breaking as the little stem going through the bag is the weakest part or the silicone adhering poorly to the bags, slipping, and sliding around. Dropping, mixing, or knocking the bag can cause these to drop off. It also means having to wait 24 – 36 hours for the silicone to go off before using the bags. Another commonly use method is gluing on a trimmed down butyl injection port like the ones I sell in my shop, gluing it on and then over sealing it with tape. Different glues melt at different temperatures so the injection ports can slide off during a sterilising cycle. You can always add the injection port after sterilising, just be mindful that the ports and site is cleaned with iso first and make sure you key the site with some fine sandpaper.
There are also methods like the ‘Peel and Stick’ stick on injection port sold by Shroom supply, however, I’m convinced this is just a sheet of rubber furniture feet, over-taped with duct tape.
Now my method is over complicated and over engineered but that’s my life story. I got an M10 pottery nipple which comes with a pre-drilled bore and a nut.
I keyed the bore with some 240 grit sandpaper to give the silicone more to adhere to.
I placed the nipple bottom on some paper and squirted some silicone into it until it came out of the top.
With the bottom still pressed to the paper, I wetted my finger with some soapy water and smoothed the silicone until it was slightly recessed into the nut face.
After 24 – 36 hours depending on temperature, I put the nut on the thread all the way to the top and left 1 – 2 threads exposed before cutting below them. Too longer nipple may cause leverage to potentially damage the bag as the grains are jostled around, though I don’t think this is as big of a deal as I initially thought. If you want to use washers to increase the mating surfaces and thus clamping force, be sure to leave adequate threads exposed before cutting. Once cut, unscrew the nut and file or sand the cut faces smooth so they minimise the chance of tearing the bag.
Finally, cut a hole in the bag. You can use any size bag but I’m using some 10T’s I’ve got. Punch, cut or burn a hole in the bag around 7mm in size. I’m using a 9/32nd hollow punch. It’s wise to make the hole smaller than the outer diameter of the threads, that way they’ll catch the threads and fill them with plastic creating an even tighter seal.
Pass the body portion of the injection port through the hole and secure it, hand tight is enough, on the back with a nut.
Easy-peasy. You now have a solid, reusable, autoclave safe bag injection port. You won’t need to wait for 24 – 36 hours for it to cure nor do you have to worry about knocking this port off. Simply hold the injection port, inject through it and go about your business.
Since I believe I came up with this method I’m calling it the Archer Port. If google is interested in the patent my price starts at 8 figures minimum.