Light and display
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What light does
It fades. Sea glass holds its colour well, shells do not, and anything with pigment or organic material in it changes under sustained light.
Which the archetype does not mention
The note for this group says clarity matters more than anything else, which is a statement about display. It is a fair description of how collections are kept and it is not a preservation position.
The shelf offers both
94 clear containers and 45 amber, with 59 white and 26 natural among the opaque options. The choice exists; the archetype simply points at one side of it.
Decide per find, not per collection
Sea glass on a windowsill is the point of sea glass. A pigmented pottery shard in the same window is being damaged for no gain.
Rotate what is displayed
The standard museum answer. A piece on display for three months a year and in a drawer for nine ages at a quarter of the rate and is still enjoyed.
Heat comes with light
A sunny windowsill is also a warm one, and cycling temperature drives moisture in and out of porous material. The two problems arrive together and the same move solves both.
Clear does not mean unprotected
A clear jar away from direct sun is fine. The failure is a clear jar in a south-facing window, which is exactly where collections end up.
Window glass filters some of it and not enough
Ordinary glazing removes a portion of the shortest wavelengths and passes plenty of what does the damage. A sunny room is not a protected one.
Fading is cumulative and invisible
There is no point at which it becomes noticeable; the collection is just gradually less than it was. Comparing against a piece kept dark is the only way to see it, which is an argument for keeping one.