This was the start of my first airlock cap attempt.
I new that I was not satisfied with our fermenting set up. Not the antique 2 gallon crock nor the one gallon glass jar with glass lid. The mold and scum, while expected, was not acceptable. Internet research had turned up fermenting systems that used an airlock but I was unwilling to spend what they where asking. So we set out to make our own airlock system.
I started by buying a half dozen, half gallon, wide mouth, Ball mason jars. Then I found a local beer making supply house that sold airlocks. So my first airlocks where constructed using the standard wide mouth two piece canning lids, a couple of varieties of airlocks and some tight fitting o-rings to seal the airlock to the lids. I also used one piece metal lids saved from grocery store products that fit standard Ball canning jars.
From these first tries I found that the o-rings did not seal well enough by themselves. And the 2 piece canning lids where not convenient to use during fermentation. All the metal lids tended to develop rust spots after repeated usage. And the one piece “S” shape airlocks where too difficult to clean.
That brings me to my present, and very acceptable, airlock cap system. The o-rings have been replaced with 100% silicone sealant. This needs to be food grade silicone, no kitchen and bathroom silicones with mildewcides. Most, easily found, aquarium 100% silicone sealants are food grade. But check the ingredient list.
They come in wide mouth and standard mouth sizes. I found them at my local grocery store along with the other canning supplies for about $3 per box of 8 caps. These are also very handy to use to cap the fermentation jars after they are done fermenting and need to be stored in the refrigerator. If not found locally, they are available on EBay.
And for the airlock itself, I have settled on the 3 piece design made by Buon Vino Mfg.- Canada. It is inexpensive and the unit comes apart for cleaning. These cylinder airlock units are carried by most beer and wine making supply stores. I have also seen them for sale on EBay, just search for “airlock”. Locally they cost me $1 each.
The actual construction of the cap system involves drilling a hole in the center of the plastic cap. The three piece airlock shaft has a slight tapper, so the hole is sized such that the airlock fits snuggly when inserted to a depth of about half an inch.
A bead of silicone is then applied around the shaft both on top of the cap and then on the underside as well. Wait a couple of days for the silicone to completely cure before using the cap.
And that is the airlock cap design I am presently using.
Future design changes: My next version will incorporate a grommet seal instead of the silicone sealant. I hadn’t already gone this route because of the cost of the grommets in small quantities and the fact that I could not find the correct size locally. I’ll post pictures when that design change is made, but until then I’m satisfied with the performance of my current airlock caps.