Re: My own PVA glue sizing experience became: dark reaction in gumemulsion

[phritz phantom <phritz-phantom@web.de>]

hi chris,
didn't the emulsions seperate? not even after a week? or did you keep 
agitating in some way?
any time i keep a mixed gum emulsion, the pigment sinks to the bottom 
after a day or so. it looks like if  it's the pigment/gum sludge at the 
bottom and the dichromate on top.

just curious,
regards
phritz

Christina Anderson schrieb:
> Phritz,
> Neither were covered.  Humidity was high (this was in MN in the 
> summer).  The one was in a dark large cupboard, the other left out.  
> The amount in both cups didn't change that I remember and I would have 
> noticed, because I measured the same amount in each--remember, it is 
> not water, it is gum arabic.  I was still, surprisingly to me, able to 
> pour both and use both for coating--in other words, I expected a 
> hardened lump but neither did so. I was most interested in the 
> difference between the two.
>
> BTW I coated the paper using both solutions mixed with pigment as 
> well, and left both out in the sun to really bake it on, and the 
> continuing action wasn't as dark as the dark reaction ones...go figure.
>
>
> Phritz, this is not a controlled scientific experiment, just a desire 
> to see the effects of dark reaction and continuing action that the 
> literature discusses so much.  With no pigment in the mix it is easy 
> to observe that both occur, but how that affects gum printing in 
> general (e.g. if someone were to mix a coating solution and save it 
> for a day or two or three--this does NOT refer to coated paper that is 
> saved a day or two or three which is an entirely different story and 
> in MT I can keep coated paper 3 or 4 days, in MN not long at all due 
> to ambient humidity there vs. here)--in other words PRACTICE, not 
> testing--is the usual YRMV. You can theorize til the cows come home, 
> but that doesn't do much good.
>
> I don't need a reason for a speed increase in my emulsion and 
> therefore just have never felt a need to let a solution age. But my 
> guess is, from the literature, that using aged emulsion is not as big 
> a deal as some of the more contemporary books say it is, so Keith's 
> question is a valid point as is Loris' saying to be consistent in your 
> testing, to take these reactions into account.
> Chris