PH on paper

[spider]

Acid-free paper is paper that has a neutral or basic pH (7 or slightly greater).
It addresses the problem of preserving documents for long periods. Paper made from
wood-based pulp that has not had its lignin removed goes yellow and deteriorates over time.
When exposed to light and/or heat, the molecules in the acidic paper will break down even faster.

The bicarbonate is added in excess, to supply the paper with an alkaline reserve to provide protection
from further attack by acids remaining in the paper or supplied by the environment
In order for paper to last at least 100 years it must have an alkaline reserve of 2% or more.

Why do today's alkaline papers contain so much calcium?
It is cheap and it gets the job done.
cost less than Titanium Dioxide, calcium provides the same benefits it's enhances whiteness, opacity,
and an alkaline pH that keeps the paper from going yellow.
A typical alkaline paper is 15 per cent by weight calcium.
According to industry experts, this is going to remain the same or get even higher,
so calcium buildup problems are not going to go away.

If the pH becomes too acidic, the solution will start dissolving the aluminum oxide non-image area.
If the pH is towards the neutral or alkaline side,
the desensitizers such as gum Arabic will stop working properly

Temperature also influences conductivity.
As the temperature goes up, the conductivity goes up, as temperature decreases,
so does the conductivity. A good rule of thumb, is for every 10° F change in temperature,
conductivity will change by 100 micromhos

Ha! Ha! .......I could go on and on

[Alex Arriaza]

Thanks for the info, but i would like to know if the properties of the paper are transfered in some way to the fountain solution or the opposite way, i believe that the solution that touches the paper in the impression roller are dragged with the paper outside the press, so the paper needs to be in certain values of PH so it doesn't have problems with tinting and post press handling, the thing im trying to understand is what are the chemical reaction i should be careful with in the process so i don't have post press problems in the future, can variations in the fountain solution due the paper conditions change the final result?
Thanks

[spider]

yes.........
acid-free paper may be treated with a mild base (usually calcium or magnesium bicarbonate)
to neutralize the natural acids occurring in wood pulp, and it may also be buffered to prevent the formation
of additional acids (as may develop from the application of sizing).
and Calcium buildup in the red ink unit you can use a calcium-free red ink and calcium fighting or a calcium fighting fountain concentrate

[mfallona]

There is a quick and dirty pH pen from Preservation Technologies.
The re-order phone number is printed on the pen: 1 800 416 2665.
Acid paper will turn yellow and neutral or alkaline paper will turn blue.