Hourglass

Designed to count down the time interval of laboratory procedures. Time value marking - on the base ( 1,2,3,5,10,15 and 20 min.)

 

The glass for the hourglass is made of the same material as all other types of blown glass. Sand is the most difficult component of an hourglass. Not all types of sand can be used, as the grains of sand may be too angular and may not flow properly through the neck of the hourglass. Sand from sunny beaches looks tempting, but is totally unsuitable for clocks because IT is too angular. Marble dust, dust from other rocks, and small round grains of sand like river sand are best suited for an hourglass. What's curious is that in the Middle Ages, books for housewives contain recipes for making glue, paints, soap, and also sand for hourglasses. Maybe the best sand is not sand at all, but glass tiny balls with diameter of 40-160 microns. Besides, such glass pellets can be made in different colors, which makes it possible to match sand glass with the interior of the room where it will be placed.