@liaizon
Eons ago corks were used for that.
@GustavinoBevilacqua thats not a bad idea thanks I didn't actually think of that option. I wonder where I could find some thick cork material in berlin
@liaizon @GustavinoBevilacqua There used to be this amazing jar & canning supply store in Berlin but they've moved out to the suburbs:https://www.glaeserundflaschen.de/verschluesse/fuer-glaeser/korkenstopfen/
Otherwise, you could check modulor or idee:https://www.modulor.de/search/kork.htmlhttps://www.idee-shop.com/search?sSearch=kork
@GustavinoBevilacqua thats not a bad idea thanks I didn't actually think of that option. I wonder where I could find some thick cork material in berlin