Kosar !!!!!! Re: Measuring humidity
On Fri, 29 Sep 2006, Christina Z. Anderson wrote: 5. PH, temperature, and moisture all affect printing speed. has anyone anywhere anytime ever doubted that??? 6. Adding an alkali to the gum/dichromate mix: if so much is added it is converted into a monochromate, and the light sensitivity drops to 25%. The higher the pH of the layer, the> longer the required exposure. Chromates, thus, are slower than dichromates.> With ammonia, you may start out with a high pH in solution, but due to> the volatility of ammonia, it evaporates during drying and the pH of the coated layer returns to a lower pH. If a solid alkali is used (sodium hydroxide or carbonate) the alkalinity of the dried layer remains the same.> The useful life of a sensitizing *solution* is greatly increased with addition of ammonia. If pH is 8 or higher, deterioration of solutions is practically nonexistent (note: not coated paper).>This may have been what started my tests of the topic... admittedly my lab conditions and instruments weren't rocket science grade, but I found that description, let's say, over-ambitious for gum. And, though I never bet less than a million dollars (or rarely), I'd bet that Kosar's sources did NOT try that prescription on gum printing -- let alone with different colors AND different gums !! (not to mention different papers, and different sizes). Just about every "source" Kosar identified, was doing carbon or similar printing, where ingredients not only sat on the surface, but action could be completed on a neutral material BEFORE transfer -- or whatever voodoo.. (and I mention that Kosar says dichromate has a straight line curve! Ha!). The results of my own "ammonia" tests are, honest, recorded -- as far as they went. And I do, honest, know where that notebook (from maybe 87 years ago) is. It's just a matter of excavating it, as in -- well, you know how they make coal ! I will do that, however, soon. 8. Paper will keep, coated, for even 70 days in the ice box, or 3 days at room temp. If paper is dried at room temp high enough to dehydrate coating,> dark reaction does not occur and consequently shelf life is very good.Of course I tried this too.... the answer was NO NO NO. At least here. (Who else has done this?) Paper in the refrigerator didn't print well after a couple of days... and what's this "3 days at room temp" supposed to mean? (Maybe if the room is an igloo.) Since none of us, I presume, are going to run hundreds of tests to prove which has a greater effect on dark reaction (what a waste of time) maybe we can be assured of saying that pH, temp, and humidity both in the air and within the coated paper has an effect on dark reaction.Of course, that's a no-brainer... But so what? That's like saying, love me, love my pit bull, my 5000 db stereo, my dirty laundry, my thieving relatives and my habit of chain smoking in bed (for starters). cheers, Judy
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