Re: vapor pressure in printing chemistry... Bob Gifford's description of
vapor pressure was helpful.
I'm not a chemist, but from working w/ these issues pretty frequently, I've
developed some home-spun understanding. If there are technical
errors/omissions, I trust our colleagues will set me straight.
Following the lead of EPA (and several states) in the Alternative Control
Techniques document (ACT), which I believe was promulgated in 1992, vapor
pressure was included as an optional method for measuring the potential for a
substance to volatilize (evaporate). The older printing CTG had set a limit
of 30% VOC for blanket washes for non-heatset litho, but the new document
allowed using the alternate measure of 10 mmHg vapor pressure. So altho a
fountain solution w/ a VP of 17 mmHg is still pretty low, it's above that
The VOC/vapor pressure model is not used by all states, so you'll need to
refer to your state's regulatory group to check status before adopting new
George Frantz MA/OTA