Pasteur's swan-neck flasks demonstrated that microbes are air-borne and do not "spontaneously generate" within flasks... even with an air supply. Utilizing gravity only, his S-shaped swan-necks kept out microbes remarkably well. For sprouting, a breathable fabric and regular water changes are advised, but even ad hoc seed sprouters don't utilize gravity from what I can tell.
Why don't they utilize gravity? Just boil the water beforehand and you won't need to change it, right?

Edited June 25, 201510 yr by MonDie

The intact flask in Pasteur's experiment kept out spoilage bacteria for long enough to show that the other broken flask cultured first, thus proving his premise. I suspect, if you leave it for longer, bacterial spores will eventually get in there to spoil it, same as in a sprouter using pre-boiled water.

May want to look into using the clean water normally only used for eventual flushing.

The intact flask in Pasteur's experiment kept out spoilage bacteria for long enough to show that the other broken flask cultured first, thus proving his premise. I suspect, if you leave it for longer, bacterial spores will eventually get in there to spoil it, same as in a sprouter using pre-boiled water.

 

Unless the swan-neck is waiting for some unique, flying microbe to come along, then a neck length proportional to the soak time should solve this.

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Is a water-"tight" seal really so tight that even an H2O molecule cannot penetrate it? This thing will have to open up for filling.

Perhaps a sterile, specially designed cloth could allow air in yet keep microbes out.

Edited July 5, 201510 yr by MonDie