warning Re: gum mixes
I hesitate to mention this, it's well known, a discussion we've had before, and Sam Wang is the picture of health... still in the context I think it needs saying -- and Chris, if you don't put caveats in your book, there will be repercussions. That is, if you cite use of dry bichromate without serious warnings, I would hesitate to put it on a reading list without reservations, and it could run into trouble with the safety police at any heads-up school.
That is, dry dichromate is the form in which dichromate is most dangerous -- by inhaling. Presumably our senior gum printers are well aware, and take care accordingly, and/or have the pulmonary powers of dromedaries and the lungs of deep sea divers. Chrome is one of the two most allergenic materials to humans and handling the dry chemical is the time it is most likely to get into the air & hence your lungs. (For that matter, any dry powder, even baby talc is potential grief...as is also well known.)
It should be spooned out, not shaken out, a long-handled instrument used so skin doesn't touch, and all surfaces, including bottle neck and table, damp-wiped after each use, etc. etc. etc. Cloths disposed of in closed containers, hands never in the mix. (Incidentally, it was commented about that AWFUL you-tube video on gum [Charlie Chaplin photographs a naked lady for clip art] that he wore no gloves -- actually during the wash period, that is, hands in the wash water, even Charlie wore gloves. And trust me, he wasn't that fast -- they'd speeded up the camera.).
But it's anyway far better to make a strong mix in liquid and dilute as and if necessary -- quicker, safer and keeps indefinitely in solution. plus wherever it is is always visible. (The fine dry powder is not -- and it does enter the air.)
We breathe enough crap in this world we can't help, why deliberately up the poison?