Wood biscuits will swell in the presence of humidity until they don’t fit their slots, but one way to keep them dry and unswollen is to use a desiccant. Those little packs of silica gel that often come in shoeboxes are perfect for this purpose. Instead of throwing them away, just put a silica pack in your container of biscuits and seal it tight. Then change it every time you get a new pair of shoes.
– Serge Duclos