This fully online parametric model allows you to create a fermentation jar from any of your used jars, jugs, or glass vases. These can be used for sourdough starters, ginger bugs, kombucha, sauerkraut, and so on.

All you need to measure is the outer diameter of the opening and the height from the top of the opening to a groove, lip, or thread on the glass that the cap will cling to. Enter those two dimensions into the parametric file, and you're ready to print.

There are additional customisation options you can explore if you'd like, including the thickness of the cap, the size of the pressure relief slits, the length and width of the pull tab, and the size of the flange that grips onto the groove of the glass. The width and length of the pressure relief slits, as well as the thickness of the cap, will affect how much pressure is required for the cap to “burp”. Play around to find what works for you. The defaults in the file work well for a ginger bug in my case.

Layer height: 0.2mm

Filament: TPU or similar flexible

Supports: None

Infill: Not really applicable unless you make the lid extremely thick

Print time: Varies according to size but I find an average lid takes about 45 minutes on an Ender 3 V3 KE

Filament usage: 10g based on an average sized (70mm diameter) cap