HPW, Vic was right about blueprints, it was the way/method of printing them with wet chemicals, hence the reaction that Vic suffered. Don't ask me what the chemicals were, but I think there was ammonia in there somewhere due to the smell. "Drawings" are still to this day occasionally referred to as blueprints, but they are now mainly laser printed.
Don't berate yourself, HPW, the job you did was very highly skilled, just in a different way. If you made a mistake someone could get badly hurt or worse! A lot of my family on my mums side were miners, so I am aware and in awe at what you guys did. I look forward to your memories on here, it brings me down to earth, and it makes me laugh at the antics you got up to. Especially that bit about buses and bait bags, that did tickle me.
I would like to meet up with you for a natter when I am up Bedders way next. Might be this summer, I will message you if I decide to come up.