Toners depend on the tiny polymer beads that they transfer to paper to form images.
For colour reproductions, these beads must be dyed, which is currently expensive, difficult and sometimes hazardous. The good news is that researchers in the USA have developed a process for dyeing such polymer beads easily and safely. The new method uses the green solvent carbon dioxide. In its compressed state, carbon dioxide already takes the buzz from coffee and the sting out of noxious, organic solvents. Now Matthew Yates and colleagues at the Los Alamos National Laboratory, New Mexico report that liquid carbon dioxide helps to turn polystyrene beads bright red.