Tin and Chrome he nearly had a hairy fit with his feet up
Tin forms stable organometallic compounds that are extremely toxic and persistant in the environment. Roman tin workings are still considered polluted ground.
Chrome causes feminization of invertebrates at the bottom of the food chain and is also persistant. Basically it's a major environmental pollutant and a major nono...........even if it does give brilliant orange colours. Tough !!
So, I will use alum, iron and copper, but I won't use tin or chrome.
I get a really good range of colours using the mordants and adjustants that I know will not, with care, pollute the environment, and really don't feel the need to do so just to get a brighter orange or glow in the dark green.