Re: Measuring humidity

[Katharine Thayer <kthayer@pacifier.com>]

On Sep 29, 2006, at 7:38 AM, Christina Z. Anderson wrote:
> My temps were consistent in SC but the humidity was consistently  
> greater down there than even the most humid day in MT will be.   
> When I did a series of gums--9 was the most I could seem to do  
> successfully at one time--the 7-9th ones were recalcitrant in  
> development.  Here I don't see a problem with 13.
I think a couple of issues are getting confused here.  As I said the  
other day, in my humid climate I would never think of coating a lot  
of papers at the same time, because I would assume that the last of  
them would be fogged by dark reaction by the time I got to them,  
although as I said, I was surprised to find that I couldn't produce a  
dark reaction the other day after 4 hours in 80% RH, even though when  
I tried this several years ago the entire gum layer was hardened in  
the same amount of time at a presumably similar humidity.  Keith's  
observation also raises difficulties, as I've already noted.

However, in my own observations re humidity and sensitivity, I'm  
referring specifically  to coatings that are printed as soon as  
they're dry, and I was assuming that the problems of printing in  
humid conditions that have been raised in these discussions  have  
also referred to coatings that are printed in short order after being  
dried.
kt