Denver and Rio Grande Western steam charter with locomotives 476 and mid-train helper 473 pull a freight and passenger train through Horseshoe Curve during our two-day charter between Durango and Silverton, Colorado on October 17th, 2023. The lead locomotive had just finished a blowdown, resulting in a rainbow in the steam cloud.

A blowdown is a way to get minerals and other contaminants out of the system. Engines want to be on a bridge or trestle because the blow down itself can reach 30+ feet at an angle away from the firebox with live steam.