A Darkroom High is when you've been in the darkroom
for so long the sun has risen and set without it coming to your attention
. You've made beautiful things
. You've accomplished so much
. You're satisfied with your existence
Oh wait, no. That's just darkroom satisfaction...
A Darkroom High is when you can barely walk after leaving your chosen isolation after twelve hours because you've inhaled enough fixer and acetic acid to kill most small mammals. That sun rising and setting stuff doesn't help though. For all intents and purposes you've lost a day from the world of the living, and your newfound mental state certainly isn't helping.
Note: a number of people I studied photography with did all sorts of wacky drugs while printing - marijuana, alcohol, ritalin, etc... I never understood why they needed it.