Acid vapors from the cabinet itself
Updated
The failure mode that makes this craft different from every other one in the estate: the container is chemically active.
The storage is a reagent
In most crafts a container either holds the product or does not. Here an enclosed drawer concentrates whatever its materials give off, and specimens sit in that atmosphere for decades.
Which means a choice of box, liner or cabinet is a conservation decision with a measurable outcome, and it is one collectors make on appearance.
The usual sources
Wood, especially oak, emitting acetic and other carboxylic acids. Worse in a sealed cabinet than an open shelf, because nothing disperses.
Adhesives, varnishes and sealants in cabinet and drawer construction.
PVC, which releases acidic degradation products including hydrochloric, acetic and formic acid as it ages. Soft, flexible clear plastics are the ones to suspect.
Cardboard and low-grade paper, which are acidic to begin with.
Rubber bands, foams and some adhesives that degrade and off-gas.
Other specimens: decaying sulfides are an acid source for everything nearby.
What it damages
Carbonates first and most visibly: calcite, aragonite, shells, and anything with a carbonate matrix.
Labels and catalog slips, which embrittle and yellow.
Metals, including native metals and metallic sulfides.
And the storage itself, which fails alongside its contents.
Choosing materials
Inert plastics rather than PVC for boxes and liners: polypropylene and polyethylene are the usual safe answers.
Acid-free, lignin-free paper and board for labels and packing.
Metal or well-sealed cabinets rather than raw wood, or a barrier layer between the wood and the specimens.
Ventilation, because a sealed drawer concentrates whatever is inside it.
And a simple physical rule that costs nothing: keep sulfides away from carbonates.