Effects Of Ph On Blue-Black Inks

October 8, 2012

pH Tests on some Blue-Black Inks.

Tests were conducted to determine the effect of pH on the color of blue-black(ish) inks.

Some papers are infamous for changing the color of some fountain pen inks. Clairfontaine paper infamously turns Waterman’s Blue-Black ink a pale teal color. The reason, as the web site so proudly declares, is that Clairfontaine is heavily fortified with Calcium Carbonate - the ingredient in Tums antacid tablets - and is alkaline. Some very cheap papers, like newsprint, are acid and can also effect ink color.

The methodology of the testing was:

1) Dilute the ink with distilled water;

2) Dispense equal amounts into three petri dishes;

3) Add a few drops of 10% S. Sulfite to the middle dish to turn it alkaline;

4) Add a drop of 3% Sulfuric acid to the right hand dish to turn it acid.

The results presented are qualitative. The ink dilution wasn’t precise and as a result some are lighter or darker in the petri dish. The pictures were taken with a flash camera set on auto - Belted Kingfisher came out quite overexposed, it is actually a dark ink. Some exposure correction was made in Photoshop to lessen variation. The amounts of alkali and acid added were just convenient quantities: they don’t bear any particular relationship to any paper, but the results with Watermans blue-black are very similar to what is seen on the page. If an ink didn’t exhibit any color change then sometimes extra acid and alkali were added just to see what might happen - the neutral inks are indeed very neutral.

First the neutral inks that exhibit very little to no color change:

http://www.nolindan.com/UsenetStuff/bbkphneut.jpg

Next the inks that lighten if they are alkaline - giving an idea of what can be expected on heavily buffered papers like Clairfontaine or Ampad.

http://www.nolindan.com/UsenetStuff/bbkphbase.jpg

Finally inks that lighten if the pH is acid. This really isn’t much concern, though.

http://www.nolindan.com/UsenetStuff/bbkphacid.jpg

Edited October 8, 2012 by Nicholas Lindan

October 8, 2012

Can I ask why use sodium sulphite to alkalise the solution ? I think using sodium hydroxide is better, because sulphite tends to break down dye molecules by destroying the double bounding between atoms of the dye molecules. sulphites can be used to utterly destroy and bleach out dye molecules, so this can be bias your test. Even you will try to increase pH to 10 with both sulphite and hydroxide, the chances are big that the sulphite treated sample will bleached out significantly.

October 8, 2012

"Beat Me Daddy, pH 8 to the Bar" just makes one wonder: why?

October 8, 2012

Can I ask why use sodium sulphite to alkalise ...

No particular reason. I'm a photographer [of the old school] and have a lot of S. Sulfite on hand.

A better choice would have been carbonate as that is what is used to buffer paper. Ink color wasn't changed much by the addition of a few drops of S. Carbonate, though. If I added enough carbonate solution to the ink it would start to alter the dilution.

Hydroxide and S. Sulfite produced about the same effects. I don't like hydroxide solutions for casual chemistry, but sulfite is rather harmless so I used sulfite.

You are right in that the inks are very sensitive to sulfite. The loss of color due to sulfite was reversible. The addition of acid to the alkalized (and now pale) ink restored the color so there was no "utterly destroy and bleach out dye molecules", as you put it; the dye molecules were merely temporarily unhappy.

The question I wanted to answer was "Are there inks that are pH insensitive?" The answer is yes: Sailor, Pilot, PR Midnight and Kingfisher to name a few. That's all the answer I was looking for.

The question "Just how sensitive is this ink to pH changes?" wasn't one I was interested in. Of course, if you would like to conduct quantitative experimentation yourself ...

Edited October 8, 2012 by Nicholas Lindan