If you read my other post on why paper acidity is important you'll know that the pH of a paper can effect how well it ages. What do I mean? Well will the paper discolour, become brittle and damage other parts of the work or will it stay in it's white, unchanged state. The chemicals in some papers can create an acidic foundation for your art. The acid can come from the fibre composition of the paper (lignin in wood pulp is high acid) or from treatments but as it breaks down it can seep that acid into the work and damage it, not what you want from a piece of work you have spent hours over.
pH Testing Pen
In my Understanding Paper Acidity article I mention the use of a pH pen to test the acid present in a paper.
They contain a chlorophenol red indicator solution. You draw a small line on the paper:
- Purple/violet = paper is alkaline or neutral (generally safe, pH 7+)
- Yellow = paper is acidic (pH below ~6.5)
These pens are inexpensive, widely available from archival and bookbinding suppliers, and give a quick visual answer.
The Paper Selection
Taking a trawl around my studio I selected a range of papers I have to hand for mixed media and print work. I chose teabag paper (of course!), deli paper, Galleria canvas texture, Kent paper, newsprint, copy paper, cold presses water colour paper, wet strength tissue (carnival), MLN Sunny (claiming to be teabag paper - it isn't) and a piece of till receipt roll. All papers that at various points I have used to create art work with.
Testing, testing...
The test couldn't be more straight forward, just draw a line on to the paper sample and leave for a couple of minutes.
The development of the result can be really quick - just a couple of seconds, other papers a little longer.
Once the results were fully developed I organised the paper samples into strength of colour. Remember the pen turns yellow or clear if it is acidic and it will be purple if it is neutral or alkaline.
Here the papers are organised from most acidic on the left to most alkaline on the right.
Not surprisingly the newsprint was very acidic, it was obvious from the slight browning it already showed. The till receipt is a similar paper so again no surprise there.
The Kent, MLN Sunny Deli and Carnival papers were a bit acidic.
The teabag paper and copy paper (this brand is just an economy brand) were the least acidic whilst the Cold Pressed and Canvas Texture papers were non acidic.
The pH pen can't give exact results, for that you need litmus paper or a pH meter but it can give a general indication.
What Have We Learnt?
Many papers become acidic primarily due to the natural breakdown of lignin - a binding polymer found in wood pulp - and the chemical residues left behind by manufacturing. These components produce acids that break down the paper's cellulose fibers, causing it to yellow and become brittle over time.
Papers manufactured from cotton, bamboo and abaca fibres are acid free as they don't contain lignin.
Knowing these facts the copy paper is a strange result as it is made from wood pulp but nowadays most standard multipurpose office paper is acid-free. It is made using an alkaline manufacturing process to ensure it won't yellow or degrade rapidly over normal lifespans. So actually it does make sense. The teabag paper is made from abaca fibres, a naturally acid free plant fibre. That's why doing an pH pen test on teabag papers from marketplace stores online can tell you if what you have bought is the real deal or that it is just a tissue.
If you are interested in buying some teabag paper please follow this link here