Fermentation bell for Ball jars

AlexEnglish, on thingiverse, remixed it and made it better and more compact, please check his model out. 

Updated model (V2) to work with modern printers (original printer was a Cupcake) and designed to fit modern canning jars.  

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Originally published on Thingiverse November 3, 2010.  This is re-upload, and adjustment, of that to preserve on a trusted platform.
 

Instructions

Print out a top and bottom piece
Optional, but recommended, put weatherstripping, or some type of sealant, in the bottom piece where it slides over jar to prevent air invading there.

Put stuff in jar to ferment (use your imagination), and put contraption on top. Fill with water so it comes below top of the breathing tube when the cap is placed in.

Let sit till fermented..

Reminder to make sure it's water tight, at least the bottom and sides...