Stundengläser

Stundengläser, or hourglasses, are timekeeping devices in which sand flows from an upper glass bulb to a lower one to measure a fixed interval. The two bulbs are connected by a narrow neck and mounted in a frame; when the upper chamber is filled, sand flows downward at a rate determined by the grain size, the interior shape, and the width of the neck, yielding a defined duration.

Origin and use: Hourglasses appeared in Europe during the late Middle Ages and were widely used on ships, in churches, kitchens, and laboratories. They provided a simple, independent means of measuring time, not requiring external power or complex mechanisms. To reset, the device is turned over so the upper bulb again becomes the source of sand.

Design variations: Stundengläser vary in size and in the time span they measure, from a few minutes to about an hour or more, depending on the device. Aesthetics range from plain utilitarian frames to ornate constructions, with materials including wood, metal, and glass. The reliability of an hourglass depends on sand properties, humidity, temperature, and careful manufacturing of the bulbs and neck.

Modern status: In contemporary settings, Stundengläser are primarily used as decorative objects, display pieces, or educational tools that illustrate principles of gravity and flow. They are generally not used as precise time standards in modern timekeeping.