All Canon and MOST *HP black-only laser printers have at least 30% iron oxide in their onboard toner cartridges. Iron oxide is what makes the image work and is why the images always fire to a lovely sepia or reddish-brown. *As of 2019 some HP Black-Only laser printers do not contain the necessary iron oxide or ferrite. Check HP’s MSDS site to check ingredients of your toner
click here for HP’s MSDS sheets