"Achieving non-toxicity for these systems means replacing the dichromate
sensitizer and secondly to avoid the practise of hardening the substrate. An
alternative sensitizer is presented and hardening is avoided by using modified
The chemistry utilised for this purpose is iron based, red-ox induced, free radical
polymerization. The sensitizer is ammonium ferric citrate, using either hydrogen
peroxide or ammonium persulphate as developer."