Brightness and electrical characteristics of powder DCEL displays have been systematically measured during both the forming operation and simulated life testing. Of particular interest and novelty are the effects of different gaseous environments on display behaviour. Forming in inert or reducing gases is slow and a new phenomenon of 'sticking' is reported where the forming rate reduces to extremely low values (<0.02 V h^-1) with an associated decrease in quantum efficiency. A new mechanism for forming is proposed centred around a changing effective barrier height for electron injection, and it is concluded that the width of the formed layer does not change during most of the forming process, contrary to previous theories. This new mechanism also operates during pulsed DC life testing of the panels which displayed the best maintenance characteristics.