At the risk of being rude, did you read this thread?

In brief summary:

--The use of Speedball sensitizer is discussed in the original post to this thread, here.

--2 possible sources for "Hardener #3" (Diazidostilbene Sodium Sulfonate, or 4,4'-Diazidostilbene-2,2'-disulfonic Acid Disodium Salt, CAS: 2718-90-3) are identified here.

--I mention having ordered samples of Diazidostilbene Sodium Sulfonate here. Though I have not had an opportunity to test it, yet.

I have not been able to track down the CAS# of the ND22 sensitizer identified on the B&S board, from PJS Chemical. But I have received a sample of a close chemical cousin, 4-Diazodiphenylamine/formaldehyde condensate hydrogen sulfate zinc chloride complex (CAS 68988-17-0), also not tested yet.

The families of chemicals discussed here (diazos and azides) are capable of polymerizing a great number of things, including gelatin, and are most likely capable of doing so with gum and casein, though I don't know of anyone who has made those efforts.

In principle, any molecule that has received enough UV energy to contribute to image formation will stay in the gelatin. Anything that did not react will either come out in the development and washing process, or be removed by the clearing bath, discussed here.

For the 2 chemicals I received samples of, and based on the MSDS sheets I received with them, I would say that handling them poses no greater risk to human health, than say, handling selenium toner powder or dichromate powders. Appropriate care should be taken to protect your eyes, skin, respiratory tract and other mucous membranes from airborne dust and direct contact. As always, it is up to the individual user to review all safety information regarding a specific chemical or process, and take all necessary measures to protect oneself.

My brief summary turned out to not be so brief, but I hope this helps.