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Sand Timer

Turning the glass

Pick how much sand to put in the glass, then turn it. The grains fall at a steady rate and the timer sounds when the top bulb is empty. Turning it again restarts the same interval.

A shipboard instrument

The hourglass is much younger than the water clock. There is no convincing evidence of one before the fourteenth century, when it appears in ships’ inventories and in Ambrogio Lorenzetti’s 1338 fresco in Siena. Its advantage at sea was decisive: water sloshes and freezes, sand does not care about the swell.

Ships ran on half-hour glasses turned by the watch, with the ship’s bell struck once for each turn — eight bells to a four-hour watch, a system still used ceremonially. A separate short glass, the log glass of fourteen or twenty-eight seconds, timed the knotted line paid out over the stern, which is where the knot as a unit of speed comes from.

The filling was rarely beach sand. Ground marble, powdered eggshell and tin or lead oxides were preferred because they flow evenly and do not clump, and the bulbs were sometimes wax-joined at the neck so the aperture could be adjusted until the interval came out right.

Why a visible timer still helps

Short glasses still do a job no digital display does as well: they make time visible to a room. A three-minute glass on a board game table settles arguments, a one-minute glass keeps a classroom transition tight, and a two-minute glass is the standard for children brushing teeth because they can see the end coming.

The sizes here run from thirty seconds to half an hour. For anything longer, a countdown is easier to read at a glance than a nearly-full bulb.

Questions people ask

When was the hourglass invented?

There is no solid evidence before the fourteenth century. It appears in ships’ inventories of that period and in Lorenzetti’s Siena fresco of 1338.

Why did sailors prefer sand to water?

Water sloshes with the swell, evaporates and freezes. Sand is indifferent to all three, which made the glass the reliable timekeeper at sea.

What is the connection to ship’s bells?

A half-hour glass was turned by the watch and the bell struck once for each turn, reaching eight bells at the end of a four-hour watch.

Where does the nautical knot come from?

From a short log glass of fourteen or twenty-eight seconds, timing a knotted line paid out behind the ship. The knots counted gave the speed.

Was it really sand inside?

Often not. Ground marble, powdered eggshell and metal oxides were preferred because they flow evenly and resist clumping.

What decides how long a glass runs?

The size of the neck aperture, the quantity of filling and the grain size. Historic makers adjusted the neck with wax until the interval was right.

Why do old hourglasses become inaccurate?

Grains abrade one another and the neck wears wider, so an old glass usually runs faster than it did when new.

What lengths does this one offer?

From thirty seconds to thirty minutes. For longer intervals a numeric countdown is easier to read.

Can I restart it without changing the setting?

Yes — turn the glass again and the same interval runs from the start.

Why is a visible timer better for children?

Because the end is legible before it arrives. A two-minute glass is the usual advice for toothbrushing for exactly that reason.

Why is the hourglass a symbol of mortality?

It became one in Renaissance art and on gravestones, where a glass with wings stood for time flying. The association with Father Time and the reaper dates from the same period.

What is the difference between this and the hourglass clock?

This one you set and turn yourself. The hourglass clock is tied to the actual time and empties on the hour.

Where to go next

Bookmark or share sand timer directly. Everything else is one step away on world clock time.