I'm pretty sure Bullock used a lot of Kodak Polycontrast but not sure of developer. He did a lot of experimental work with light, like defractracting thru large chunks of glass. Edna Bullock showed me his studio when I was there visiting and pointed out a large chunk of glass he used. It was a fragment of a lense from a large telescope from an observatory. He held several pattens I believe having to do with solorization.