Inks: Report on the pH of More than 60 Inks

(This page revised October 23, 2016)

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This article is the work of John Smith. My contribution is editorial: rearranging the material, augmenting it slightly for improved clarity to the lay person, and rewriting for stylistic consistency with the rest of this site.

Ink smearA question that is on the mind of every inkophile who ever lived is “Will this new ink, the one with a color to die for, eat my favorite pen?” The answer is maybe. How acidic or alkaline an ink is (its pH), although this is not the only factor in how corrosive an ink will be, can affect how friendly that ink is to various pens.

LAb glasswareAlthough we often speak casually about pH in various walks of life, pH is actually a complex scientific subject. Moreover, measuring pH accurately requires some fairly expensive equipment and a thorough understanding of how to use that equipment properly.

To the chemist, pH is defined as the decimal logarithm of the reciprocal of the hydrogen ion activity, aH+, in a solution. Stated more simply, it is a measure of the acidity or alkalinity of the solution. pH is measured on a scale from 0 to 14, with 7.0, the pH of pure distilled water, being neutral. The lower the pH, the more acid the solution is; conversely, the higher the pH, the more alkaline the solution is. An alkaline substance is referred to as a base.

The task of measuring pH is far removed from taking a temperature reading or from taking a simple electrical measurement with a voltmeter or ammeter. A pH meter, and more particularly the electrode it uses, is a little miracle of complex science and engineering. Many user-generated errors can operate to make a reading unreliable. As a result, unless the source is known, your first reaction to any reported pH reading should be a sensible suspicion. I trust John Smith, who ran the tests that are reported in this article; and I trust his equipment and his methodology, both of which are described below.

Apart from user-generated errors, many factors can be regarded as contributing to variations between readings from different sources. The following list describes three such factors:

Lab 870

The Equipment

The apparatus used was an SI Analytics Lab 870 benchtop pH meter coupled with a virtually new SI Analytics BlueLine pH 15 all-glass electrode that was fully pressurized before the tests. It has an integrated negative temperature coefficient (NTC) temperature sensor. This is a sophisticated, laboratory quality pH meter with Stability Control, automatic buffer-set recognition, electrode diagnostics, and full spectrum error reporting.

The Methodology

The instrument was calibrated to two points using fresh Schott DIN Technical calibration fluids at pH 7.0 and 4.01 at 25° C (77° F).

Ink smearAll readings were established using the instrument’s Stability Control. Using Stability Control allows the instrument, not the user, to determine when the reading is optimal and stable. In this way, accuracy and reproducibility of readings in chemically complex solutions is greatly enhanced.

During the testing, the calibration was regularly checked against the buffer solutions, and no drift was detected. Standard laboratory practices were followed throughout the testing, and a random selection of inks was retested the following day.

At the time of the tests, none of the inks tested had been open for more than 18 months.

Note
Note
While pH is an important factor in the safety of a given ink, it is not the only criterion. There are other factors to consider, such as the ink’s tendency to clog, its ability to lubricate well, and whether it stains and/or damages pens and other surfaces. For more information about inks and their behavior, read Inks: The Good, The Bad, and the Ugly.

The Results

In the following table, results are listed from lowest pH (most acidic) to highest (most alkaline/basic). As a basis for comparison, distilled white vinegar, a weak acid, usually has a pH of about 2.4 at the standard strength of 5%. Chlorine bleach, a weak base, has a pH of about 11.


Manufacturer Ink Color pH at 22° C (71.6° F)

Rohrer & Klingner Salix Ink color sample 1.53
Rohrer & Klingner Scabiosa Ink color sample 1.73
Rohrer & Klingner Magenta Ink color sample 1.99
Rohrer & Klingner Königsblau Ink color sample 2.09
Pelikan Turquoise Ink color sample 2.30
J. Herbin Bleu Myosotis Ink color sample 2.31
Diamine Blue Velvet Ink color sample 2.42
Rohrer & Klingner Leipziger Schwarz Ink color sample 2.42
Diamine Red Dragon Ink color sample 2.48
Montblanc Royal Blue Ink color sample 2.57
Private Reserve Electric DC Blue Ink color sample 2.65
Diamine Sargasso Sea Ink color sample 2.66
Waterman Tender Purple Ink color sample 2.69
Diamine Asa Blue Ink color sample 2.71
Cross Blue Ink color sample 2.85
Diamine Royal Blue Ink color sample 2.93
Yard-O-Led Blue Ink color sample 2.97
ST Dupont Royal Blue Ink color sample 3.38
Parker Quink Blue-Black Ink color sample 3.40
Diamine Majestic Blue Ink color sample 3.52
Pelikan Violet Ink color sample 3.76
Diamine Purple Pazzaz Ink color sample 3.83
Diamine Eau de Nil Ink color sample 4.09
Waterman Absolute Brown Ink color sample 4.50
Pelikan Edelstein Sapphire Ink color sample 4.51
Noodler’s Baystate Blue Ink color sample 4.53
Diamine Delamere Green Ink color sample 4.59
J. Herbin Rose Cyclamen Ink color sample 4.67
J. Herbin Emerald of Chivor Ink color sample 4.69
Visconti Blue Ink color sample 4.92
Private Reserve Tanzanite Ink color sample 5.32
J. Herbin Bleu Océan Ink color sample 5.65
Diamine Autumn Oak Ink color sample 5.75
Private Reserve Blue Suede Ink color sample 6.02
J. Herbin Ivy Green Ink color sample 6.03
Diamine Syrah Ink color sample 6.04
J. Herbin Violette Pensée Ink color sample 6.20
J. Herbin Amber Ink color sample 6.28
Diamine Burnt Sienna Ink color sample 6.58
Private Reserve Black Cherry Ink color sample 6.59
Rohrer & Klingner Cassia Ink color sample 6.73
Rohrer & Klingner Alt Goldgrün Ink color sample 6.73
Pelikan Edelstein Amethyst Ink color sample 6.81
J. Herbin Vert Empire Ink color sample 6.96

Neutral Point, Ph 7.00

Diamine Ancient Copper Ink color sample 7.06
Diamine Wild Strawberry Ink color sample 7.16
J. Herbin 1670 Rouge Hématite Ink color sample 7.35
J. Herbin Poussière de Lune Ink color sample 7.55
Lamy Black Ink color sample 7.55
Diamine Pumpkin Ink color sample 7.64
J. Herbin Lie de Thé Ink color sample 7.66
Pilot Namiki Blue Ink color sample 7.73
Rohrer & Klingner Verdigris Ink color sample 7.98
Noodler’s Apache Sunset Ink color sample 8.40
Pilot Iroshizuku Take-Sumi Ink color sample 8.56
Sailor Sei-Boku Ink color sample 8.61
Pilot Iroshizuku Yu-Yake Ink color sample 8.74
Pilot Iroshizuku Shin-Kai Ink color sample 9.39
J. Herbin Rouge Caroubier Ink color sample 9.42
Pilot Iroshizuku Yama-Budo Ink color sample 9.47
Pilot Iroshizuku Asa-Gao Ink color sample 9.60
Rohrer & Klingner Morinda Ink color sample 9.76


Notes:
  1. “John Smith” is a pseudonym for a respected expert in the field who has asked to remain anonymous.

  2. The inks listed here are obviously not all the inks that exist. These are the ink that Mr. Smith had available for testing. His contribution has been entirely voluntary, and I do not consider it proper to demand that he purchase more inks specifically to pad this article. Should he test additional inks in the future, they will be added to the list.


The information in this article is as accurate as possible, but you should not take it as absolutely authoritative or complete. If you have additions or corrections to this page, please consider sharing them with us to improve the accuracy of our information.
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