Re: How can I measure the pH in differnt types of paper and is it important?

Thanks for the question, Harry.  Measuring the pH of paper is a topic that 
I have discussed at length with colleagues.  There are two main types of 
paper, as far as pH  goes.  The first is acidic and the other is 
alkaline.  Some people talk about neutral paper, but neutral and alkaline 
papers are both made at about the same pH, between about 6 and 8.  

As far as measuring the pH, you can do what you suggested, mixing torn up 
paper with distilled water and using a pH probe.  I would suggest mixing 
the paper and water with a blender to speed up the process and release all 
the components of the paper into the water.  

Another possibility is to place a small drop of distilled water on the 
paper and let it sit for a certain amount of time (30 seconds or so) and 
then measure the pH with indicator paper or a flat bottomed pH probe.  

In the paper industry, we are mainly interested in whether the paper is 
acidic or alkaline, not exactly what pH it is.  There is a special pen 
that we use to mark the paper.  If you draw on acidic paper it would write 
in a certain color, for example pink.  If you mark the alkaline paper it 
would be another color, for example purple.  

Acidic paper is still very common in the world because it is much easier 
to adjust the water resistance properties of acidic paper than it is for 
alkaline paper.  Therefore you will find acidic paper in milk and juice 
containers or anything that requires control of the water resistance 
properties.  

Most writing papers made today are alkaline because they are more 
resistant to color degradation and they are less expensive to make.  This 
has been the case in the US for several years, prior to which, the bulk of 
all paper made was acidic.  

I hope this sheds some light on your question.  I can certainly go into 
more detail if you want.  Good luck with the project.