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Inks: Report on the pH of More than 60 Inks

The important information on this page is direct from RichardsPens.com and is used with permission.  Only minor changes were made to avoid interrupting the flow of our website.

(This page revised October 21, 2016)

This article is the work of John Smith.[1] 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

  • All pH readings are temperature dependent; thus, a pH reading can only be expressed accurately in the form “x pH at y temperature.”

  • Over time, natural chemical reactions within a bottle of ink can alter the pH of the ink, especially once the bottle has been opened and carbon dioxide has entered.

  • Not all batches of the same ink are necessarily identical. This is especially important to note in light of the fact that some ink manufacturers introduce slight formulaic variations periodically to aid law enforcement in the forensic analysis of writing samples.

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

Neutral Point, Ph 7.00

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


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

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