thumb|A typical wooden breadbox.
A breadbox (chiefly American) or a breadbin (chiefly British)
Working theory
Stale bread is colloquially called "dry", but drying and staling are distinct processes. Stale bread can weigh the same as "fresh" bread, indicating almost no loss of water; conversely, bread can be dried out without going stale. Staling is a process of retrogradation, in which the starch transposes to a crystalline form in the presence of the water contained within the bread itself. The process speeds up at cooler temperatures, such as under refrigeration, and thus bread stored at room temperature remains fresher for longer periods than refrigerated bread. Frozen bread, however, traps the moisture as ice, and prevents the staling process.
Breadboxes are thus designed to:
- keep their contents at room temperature, prolonging edible storage time;
- have a lid loose enough to allow airflow, reducing condensation, which helps to prevent the formation of mold;
- have a lid tight enough to slow the drying process as well as to protect the contents from mice and all other pests, including ants and flies.
As a saying
The breadbox is commonly used to describe the size of other objects, a sense that has outlasted its routine use in the kitchen. The query "Is it bigger than a breadbox?" was popularized by Steve Allen on the American game show What's My Line?, where it became a running gag after he initially asked the question in 1953. It remains a popular question in the parlor game 20 Questions.