Now Elmo Iscariot has sent over some material that's making me rethink how I approach those seals.
I was just perusing a Wikimedia page with photos from the Arabia Steamboat Museum, in Kansas City, MO. The Arabia sunk in 1896 and settled under the mud in the riverbed. Over the next century the course of the river shifted, and eventually a team of archaeologists excavated the site. Because the ship was carrying commercial goods to the frontier, the museum is like a fully stocked mid-19th centurygeneral store.
This is fascinating enough by itself, and there's probably plenty there of interest to propmakers, but one thing in particular made me think of you. The bottles were all packed with their corked ends dipped in wax, so the contents are still intact, a century and a half later.
He included links to some photographs of bottles from the collection. Like these pickles:
Just look at that. These things are over a hundred years old and they look like they were bottled yesterday. I'm sure being buried in an oxygen free environment helped, but the level of preservation is simply amazing. Note the wax seal- it's just a single layer.
He also pointed out an assortment of preserved "pie fruit":
Again, they're amazingly preserved. You can also see the variation in the length of the wax seals from workers dipping the bottle tops.
Here's the real prop porn- vintage medicine bottles:
These are almost identical to some of the bottles I've used for prop specimens. There are two insights to be taken away from this particular picture. The first is, again, how rudimentary the wax seal on vintage bottles actually was. Instead of the great knobby bulbs I've been using the wax is a single thin layer. The thick buildup of wax present on many prop bottles may be appropriate for something crudely sealed at home, but professionally made items will have just enough wax to ensure an airtight seal.
The second item of note is the lack of paper labels. They just don't hold up over time unless the bottle is in a protected environment free of moisture and light. That makes me feel a bit better about the heavy weathering I've been using on my labels.