Eh, it's enough to hurt, but I wouldn't call it dangerous to most reasonably-healthy subjects. 300 pF is probably about what you get from the aquadag in a CRT.
That depends on the size of the CRT, etc. obviously, but I figure once you get past the level of about 100 pF and up past the 10-12 kV range, you're crossing the line into danger territory.
It's not likely that you'd kill yourself electrically with the < 1J energy unless you're really,
really unlucky, but you quickly get into the territory of being able to injure yourself from the jolt once you get past the typical old B&W tube level (say about 100 pF at 12-15 kV max for those old tubes) and into the larger-tube color TV range with more capacitance and higher voltages. You quickly pass from the annoying zap you get from a large static discharge into the "so I woke up smoldering in the corner against the wall" zone.
I built a ridiculously high power version of "The Big TC" tesla coil from the July 1964 issue of Popular Electronics back in my highscool days, using
three of the big window-glass capacitors instead of the recommended one, or the insanity-level
two capacitors as listed in the article, as well as
two high voltage transformers in series driving the primary spark gap. I didn't die. None of my friends there playing with it died. I never even zapped myself with it as I already had a healthy respect for HV, especially something that can throw an arc 18+ inches at 300+ kV. The EM radiation from that beast is strong enough that it erased the autodial memory contents from a GE 2-line desk telephone located 30+ feet away, sent 1980s-era electronics into hissy-fit mode, confused microprocessors from the other side of the basement, etc., but I didn't ever zap myself. You really don't want to zap yourself with those levels, even though you probably won't
die. It is going to seriously hurt, though.
My worst zap ever was actually a static discharge. We were stacking up those padded gym floor mats that velcro together one day in one of the basement gyms at my high school. The entire floor of the gym had been covered with them for some wrestling thing or something. As we dragged them across the floor and stacked them, they built up crazy high static charges, which was kinda fun, people got zapped a bit, ha ha, hardy har har, etc. It started to get a bit sketchy though with one of the big stacks of mats. You could FEEL the static from farther and farther away as that particular stack grew and none of the static had been discharged from that stack somehow. All the girls' hair were sticking out at it, and we were literally just throwing the folded mats onto the top of the pile from a distance since nobody wanted to go near that stack anymore...
I was standing about 20 feet away, laughing at the situation when I made the unfortunate decision to point at it and say "somebody's gonna get zapped by that pile, you can
FEEL the stati........" when suddenly there is this
SNAP as a freakin' lightning bolt jumped from the stack of mats to my awaiting, pointing finger.... Dear
god did that hurt. Oh, wow did that hurt. I literally fell down.
People were laughing and asking me if I was dead because at least something like 10 other people were looking directly at me pointing at the thing, taunting the pile at the time and SAW the giant spark jump. DAMN, did that ever hurt. I couldn't move my arm for several minutes, it was just seering pain... My arm even still hurt the next day. I was actually starting to think I had permanently damaged something but it did finally go away. I'm fine, but like I said, I have a healthy respect for high voltage, regardless of the actual number of joules involved.
To the OP... Please, just
do be careful.
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