Timer sand

A sand timer, also commonly known as an hourglass or sandglass, is a device used to measure the passage of a specific interval of time.

​Key Components and Function:

• ​It typically consists of two glass bulbs (chambers) connected vertically by a narrow neck (passage).

• ​One of the bulbs is filled with a measured amount of fine, dry, granular material, historically referred to as "sand," though materials like powdered marble, eggshell, or tin/lead oxides have also been used.

• ​The material flows by gravity from the upper bulb, through the narrow neck, and into the lower bulb at a regulated, consistent rate.

• ​The duration of time measured is determined by factors such as the quantity and coarseness of the material, and the width of the neck.

• ​Once all the material has trickled to the bottom bulb, the measured time interval has passed. The device is then inverted to start measuring the interval again.

​Historically, sand timers were a dependable and accurate measure of time, used in homes, churches, and on ships as an inexpensive alternative to mechanical clocks. They are still used today for short-time measurements (like for games or cooking) and as decorative items.