Desiccants
On this page10
What the guidance says
Metal objects can be stabilised in a dry microclimate using desiccants such as silica gel or montmorillonite clay. The microclimate is the point; the desiccant is how it is held.
It has to be in a sealed container
A desiccant in an open box is a desiccant absorbing the whole room until it is saturated, which happens quickly. The seal is what turns a small amount of silica gel into a lasting effect.
What the catalog holds
Three fibre desiccant pouches. That is not a wide range, and it is enough to make the sealed-jar approach work, which is the point of mentioning them here.
Conditioned silica gel
Guidance on metals refers to desiccants conditioned to 0 to 10 percent RH for the dry end. A pouch straight from a packet is usually dry; one that has sat open in a workshop is not, and it will add moisture rather than remove it.
It saturates, and then it is just a bag
Silica gel has a capacity. Once reached it stops working and the jar quietly returns to room humidity. Indicating gel changes colour, which is the cheapest way to know.
Which is why the label carries a date
When the jar was sealed and when the desiccant was last changed. Without that the system depends on memory, and memory is what fails over the decades this craft works in.
Size it to the volume
A large pouch in a small jar is harmless and a small one in a large jar is slow. Both are better than none, and the jar sizes here run 6 to 250 mL, which is a small volume to dry.
Regenerating it is possible and fiddly
Silica gel can be dried and reused, with heat, carefully. For the cost of a pouch against the risk of getting it wrong, replacing is usually the better answer for a domestic collection.
Keep the spare pouches sealed
A bag of desiccant stored open is a bag of desiccant that has already done its work on the room. Keep the spares in something airtight, which is the same thing this property recommends for everything else.