I've only ever seen boy tanks. How do they make baby tanks if there aren't any girl tanks?

As an aspiring glass artist I would like to replicate the irridescence found on carnival glass. All of the references I've found so far just say they used various metallic salts without identifying them. I'm guessing many were proprietary. But I was curious if you guys have some ideas what they might have used back in the 1908 - 1930 time frame.