hi there
sorry i didn't see this until now ( im asleep at the switch ! )
thats weird that it was the washing soda ..
i have some that is 2 years old in an open box that i use with no issues
and it is probably closer to baking soda by now than washing soda
the vit c tablets, was there anything else in there ?
perkolated coffee i ALWAYS use but if it isn't robusta you won't get any images at all.
the jury's out on what it is the active ingredient in the coffee that actually develops the film
some say it is the caffic acid or something else mystical .. but it isn't in arabica beans ...
glad to see you got it working !