Why does the city of Chicago dye its river green? How long does the color last?

Saint Patrick’s Day is a big celebration for the Irish. It celebrates the feast day of the Romano-British Bishop Patrick who lived in the fifth century. It’s not just Irish people who celebrate it however. Due to many centuries of Irish emigration to America, and the historic links thus fostered, many Americans mark the date in the diary.

The cities which take the celebrations most seriously are those with the most Irish heritage, like New York, Boston, and especially Chicago. One special tradition in the Illinois city is the dyeing of the Chicago River bright green, the colour of Saint Patrick.

The first dyeing of the river happened in 1962. The dye itself is not actually green. It is orange but reacts with the water to turn it green.

The Paddy’s Day celebrations were resurrected in the city in 1956. The Shannon Rovers Irish Pipe Band leads the parade to this day.

How long does the color last?

The biodegradable dye needs to be viewed quite quickly; it only lasts for a few hours before the river returns to its usual colour.

“We always refer to it as ‘leprechaun dust,’” Tom Rowan, part of one of the two families that create the dye explained to the Sun-Times. “We have never told anybody what it is.”

Originally the dye used was 100 pounds in weight.