Am looking at different food/cooking alternatives to improve health. As such, one of the local live/raw food places held a class last week about fermenting vegetables, and mentioned that canning jars might be ideal for small batches to try things out, hence this thing was created.. As an example of fermentation, look at a random book on amazon about it (http://www.amazon.com/Wild-Fermentation-Flavor-Nutrition-Live-Culture/dp/1931498237/ref=sr_1_1?ie=UTF8&qid=1288841311&sr=8-1).
When fermenting, it releases carbon dioxide, and the goal of this thing is to keep regular air from getting at the food. If air does get at it, the food can, and most likely will, spoil and be not so good to eat. This cap is designed to fit over one of the old style Ball Canning Jars, the ones with the glass top and wire holding it on. Tried to make it somewhat easy to parameterize... hopefully....
Have not tried fermenting food using this yet, most likely soon. Am not too concerned about using ABS for this, as it won't come in contact with food. If you are concerned, use a different type of plastic, or something from the frostruder.
Have printed this out and prints fine on my bot, but the handle isn't according to the stl file, but it works. Make sure to adjust your settings to print this water/air tight (at least the walls and the bottom).
The idea is to fill the middle part with water, put food in jar, put top on, and put cap on top of that to seal everything in, then wait couple weeks. Might have to put something in the gap (like weatherstripping material) to fully seal the plastic top with the glass jar.
It is recommended to use a finely tuned printer...
Feel free to use and modify this as you want. No clue on the licensing so tried to pick an open one... And thank you again to Catarina Mota for her shapes.scad file (included)!
NOTE: In the picture with the brownish liquid, that is actually apple cider I used to provide some contrast, so don't get the wrong idea.. :)