How much is known about the Green Dye used in the Chicago River?

Question

Being I have never visited Chicago, I first learned on Wikipedia that Chicago dyes its river green on St. Patrick's Day. The Wikipedia article, as well as many sources, say the dye ingredients are a top secret. However, other sources know bits of information about it. (One site says it is a vegetable dye, other sources say it is a fluorescent dye ) How much is known about the properties and ingredients dye used in the river? One newspaper I saw online said over 50 cities wanted to know the formula. Even though the formula is not being released by the group doing the dying, but because the river is publicly accessible, I would presume that someone has taken samples of its water to a chemical lab for analysis.

So, is the green dye used in the Chicago river still a big secret?

Answer 1

First, I do not know. But if I were doing it, I would use eosine. This is a cheap dye that looks orange, but when the sunlight hits it, it fluoresces green. This means that the light orange doesn't show much, but the brighter the light, the more intense this green glow. Also, if I were in Chicago, I would not want to use any thing dangerous, and eosine is long known. Long ago, there was a household cleaning solution called **** 'n Span. That was dyed with eosine.