U of S | Mailing List Archive | alt-photo-process-l | Do dichromates change with age?

Do dichromates change with age?

Has anyone come across any data about whether dichromates losing speed, or effectiveness?

My jar of ammonium dichromate is probably over 20 years old (yeah, I use very small quantity in gum printing) and it appears to suddenly need longer exposure time. Doesn't make sense, especially since I'm using an Amergraph printer for exposure. Humidity and everything else has been kept fairly consistent.

Anyone else has similar experience?