I've just discovered this today, I didn't know you could use coffee as a developer.
A quick google led me to the Shutterbug site which said 'caffeine, as found in Tea or Coffee... can be used as a deveoper but coffee is best to use as the concentration is higher than in tea..."
Well, being British maybe, I was actually drinking a cup of tea at the time. Hmmm, I thinks...
Well, I don't want to upset anyone from across the pond, but...(searching for ways to put it tactfully...) whenever I've asked for tea in the USA I've been given a tiny bag of something fastened to a bit of string with a staple and a tiny pot of tepid water to dunk it in, usually with a lemon slice on the side.
Well, that is
not tea!

Well, not as we know it...
I reckon the purpose of the staple is to give the water a bit of colour as it rusts. I can imagine the caffeine content is as weak as the taste is insipid.
Now, Tetley's or PG-tips, a generous teaspoon per person and one for the pot (pre-warmed, obviously

) contains LOTS of caffeine. At least on a par with instant coffee.
I brewed up an extra strong pot, chucked in two heaped teaspoons of Sodium Carbonate, made a quick test print and... Nothing.
Very little, anyway. There was a tiny ghost of a hint of an image, that was all. I used RC multigrade paper, so this could be developer incorporated. I next tried an old graded paper and this time got absolutely nothing whatsoever, so the ghost image was probably just the effect of the warm carbonate solution on the paper.
Strange, I checked the caffeine content of my tea on the web and my belief that it contains useful amounts of caffeine is correct. I did a bit more research and discovered this on wikipedia:
"Caffeic acid may be the active ingredient in caffenol, a do-it-yourself black and white photographic developer made from instant coffee. The developing chemistry is similar to that of Catechol or Pyrogallol...
Caffeic acid... is unrelated to caffeine"
So, that was just a quick 20 minute wander up a blind alley for me, but it looks like it is the caffeic acid in coffee that does the trick and tea is best left for drinking. A bum steer from the shutterbug site!
I also discovered, when googling for 'Caffeinol', it appears that the health proffession have adopted this name for a recomendation to high risk victims to drink a combination of coffee and alcohol to protect from strokes.
When googling for 'Tea developers' you get lots of hits, but here TEA is an acronym for triethanolamine, which
is an active developing agent.