There are 2 routes you can go down with making AirPort Jars. Both achieve the same objective, however the professional one looks better and has a slightly lower risk of contamination as the polyfill air filter can induce ‘Wicking’ where the mycelium can make contact with the air filter and any contaminants that are caught in the filter.
Route 1: Cheap and cheerful, requires RTV silicone and polyfill (pillow stuffing)
Route 2: More professional looking, requires Self-healing injection port, syringe filter and epoxy.
The way I worked when I first started was to find the biggest jars that will fit inside your pressure cooker, I got mine off eBay but you can get them at every hobby craft store in the country or just use old jars you have lying around.
Wide mouth jars are the best as narrow mouth jars can make getting the spawn out tricky. The best practice would be to buy them new to possible stress fractures as well as ensuring they have the silicone seal around the inner rim as seen in the photo below of the inverted lids.
Take your lids and puncture 2 holes in them, around 7mm in diameter. One in the center and one off-set is fine. You can do this using a drill, a punch set or even a pro hole puncher. Using a drill can prove messy as the thin metal of the lid will chew before it cuts, leaving a jagged edge. If you use a punch, make sure it is supported on the underside of your work surface to not bend or dent the metal.
I chose a professional metal punch from Amazon as it gives the cleanest cut, an ordinary paper punch might work too however, if I was feeling devlish, I might say order it off Amazon, use it and return it.
Take your High Temp RTV Silicone and squirt a bead around the centre point hole you’ve made. Dip your finger in water and soap and work the silicone in a circular motion until the hole is sealed up. Remove your finger upwards from the centre of the silicone, wet your finger again and press it flat so it ‘mushrooms’ out over the rim of the hole.
Once it sausages out of the backside, repeat the process so you’re creating a kind of overfilled sandwich effect, this will help prevent ripping the port through once you’ve skewered a needle through it. Make a mark on the top side of the silicone which denotes the ‘centre’ of the hole, so you don’t try to inject into the lid obscured by the silicone. Leave it to cure for 12 – 24 hours.
Next, take some polyfill and extrude it until its wispy. Then fold it back on itself and back on itself again, do this until it is a thick web of polyfill but not overly ‘tight’. Poke it through the hole with a pen or your fingers until it is half outside the lid and half inside the lid.
Cut off or pull through excess polyfill to prevent wicking and replace the polyfill as you see fit. She ain’t pretty but she is functional.
Punch your holes in the same place on the lid, making sure the outer-most hole isn’t too close to the edge of the lid as the syringe filter will overhang some-what. Next, take your high temperature epoxy, I use Gorilla Glue Epoxy and mix together the resin and hardener. Don’t use the RTV silicone, it is not a bonding agent and will fail when you knock the ports.
Take your syringe filter and on the barbed side (that would fit into a luer lock syringe) put a bead of epoxy on the blue rim of it. You’ll see that the top has more perforations/vents which will indicate which way up the filter should be.
Pass it through the hole and secure it against the lid of the jar by holding it firm for a few seconds and twisting slightly to remove air pockets. Then make a small bead of epoxy on the underside of the lid to prevent rusting.
Next take your self-healing injection port and put a bead of epoxy around the underside lip and push it through the central hole of the lid. Using tweezers and a tooth pick is the least messy/fiddly way of doing this.
Pass it through the hole and secure it against the lid of the jar by holding it firm for a few seconds and twisting slightly to remove air pockets.
I know which one i’d put on a Christmas card that’s for sure. There are other ways of making jars, some use Tyvek or permeable gaskets but all achieve the same end. I prefer the ‘pro’ lids because they require less maintenance as every now and then you need to replace the polyfill or re-set the ports, the epoxy makes these lids pretty permanent. The cost difference is practically negligible, in my experience if you’re running more than 30 jars at once you should be looking to upgrade to bags.