What makes the Chicago River green for St. Patrick's Day? No, it's not ground-up leprechauns. It's a vegetable-based dye. In the early days though it was a substance called Fluorescein.
What makes the Chicago River green for St. Patrick's Day? No, it's not ground-up leprechauns. It's a vegetable-based dye. In the early days though it was a substance called Fluorescein.