Over the years I've had several failures to seal with bottles with a cardboard seal, (maybe 1-3%). I never had a failure with caps with a seal like these https://packagingoptionsdirect.com/1...thread-closure. Be sure the cap matches the threads on the bottle. In that type cap I've sealed thousands of bottles with zero failures.
The ones I like best have a soft plastic (nylon?) seal part way down the cap, and a top quality seal in the very end of the cap. If sealed properly, in glass syrup will last 20+ years just keep it out of the sun to maintain grade.
Dave Klish, I recently ordered a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.