Are you saving seed for next season? Mason jars are a tool for processing seed from wet seed crops like tomatoes and cucumbers.
Simply put seedy pulp of the same variety into mason jars and let them sit in a well-ventilated area for several days.
The wet pulp/seed mixture will start fermenting and will form mould on the surface during the process.
The fermentation action works to separate pulp and seed with seed falling to the bottom of the jar and the pulp rising to the top.
When this occurs, the pulp and liquid can be poured away leaving the seeds ready for drying.
Tip on time to harvest: Tomato seeds should be harvested when the fruit is ripe while cucumber seed can be harvested from over-ripe and discoloured fruit.