Chemistry for Everyone
Chemical Composition of a Fountain Pen Ink J. Martín-Gil,* M. C. Ramos-Sánchez, and F. J. Martín-Gil Laboratorio de Química Sostenible, Departamento de Ingeniería Agrícola y Forestal, Universidad de Valladolid—Escuela Técnica Superior de Ingenierías Agrarias, Palencia-3407, Spain; *
[email protected] M. José-Yacamán Laboratorios de Microscopía Electrónica de Barrido y Difractometría de Rayos-X, Instituto Nacional de Investigaciones Nucleares, México, D. F., México
The manufacture of ink is associated with the graphical arts, but it is classified as part of the chemical industry. It is paradoxical that a substance so easily definable as a fluid or viscous material used to write and to print has reached such a level of complexity and specialization that almost a million new formulas appear every year. Within this context, a study of a particular ink makes the characterization, as far as possible, of its chemical composition and subsequent classification necessary. In the case of black ink, this classification is typically in one of the three prominent ink types: gallotannate (also called iron-gall) ink, Chinese ink, and printers’ ink. The gallotannate ink is made from monohydrated gallic acid, crystals of ferrous sulfate, and gum Arabic (Figure 1). In agreement with the Babylonian Talmud, black ink was discovered by Tanna Rabbi Meir (second century C.E.) as reported by Nir-El and Broshi (1). Chinese ink is made with carbon black, fish glue, indigo, and camphor. Its primitive formulation, with carbon black in emulsion with vegetal pigments or animal oils, dates back 4500–5000 years. Printers’ ink (analogous to ballpoint pen ink) uses varied pigments and includes desiccants (compounds of calcium and iron), waxes, fats, rubber, and varnish in its composition.
The different compositions of inks influence their permanence on paper. There is agreement that the main cause of variation of written text is the iron(II) sulfate content of the ink, whose effect is stronger than the destructive action of the acids. The mechanism that traditionally has been cited is oxidative decomposition of the cellulose by means of the free radicals that are generated after the formation of unstable complexes of metallic ions with molecular oxygen (2): • Formation of the organic hydroperoxide (ROO•) and other organic radicals
Fe2+ + O2 Fe3+ + O2• − + RH
R• + O 2 ROO• + R′H
Fe3+ + O2• −
(1)
R• + HOO• + Fe2+ (2)
ROO•
(3)
ROOH + R′•
(4)
• Formation of hydrogen peroxide + Fe2+ + HOO• + H
Fe3+ + H2O2
(5)
• The Fenton reaction
Fe2+ + H2O2
− Fe3+ + HO• + OH (6)
The iron salt-dependent decomposition of hydrogen peroxide generates the highly reactive hydroxyl radical, possibly via an oxoiron(IV) intermediate. Other equally important reactions are those of the iron(II) sulfate reduction to pyrite by the action of certain microorganisms (Desulfovibrio desulfuricans or Desulfotomaculum nigrificans) (3, 4): gallotannic acid
− + 2CH2O + SO42 + 2H a carbon from source bacteria
(7)
H2S + 2CO2 + 2H2O gallic acid
Figure 1. Galls such as these have been widely used in the production of inks. Ink recipes require that the powdered or crushed galls be boiled for several hours (to release the tannins) and that the resultant solution be fermented by mold. As the mold enzymatically digests the gallotannic acid, the solution is transformed to gallic acid. Gallic acid will produce a purer black color in reaction with iron sulfate, while gallotannic acid will produce a comparatively browner pigment.
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+ Fe2 + H2S
FeS
+ 2H+
− + RCHOHCOOH + Fe2 + SO42 from components of the ink
RCOOH + 2CO2 + H2O + FeS
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(8)
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Chemistry for Everyone
The conversion to pyrite and its subsequently loosening from the paper leads to the partial loss of the indelible character of the majority of inks and to the loss of clarity in the writing of the documents (5). The objective of this article is to examine if Parker Quink ink, widely used in 1950–1980 for fountain pens, will provide the permanence necessary for the preservation of documents. Quink ink, a combination of Quisumbing and ink, was invented and sold to Parker by Philippine chemist Francisco Quisumbing and began to be used in the 1930s. Material and Methods The samples examined are the viscous remainders of spontaneous evaporation of the Parker Quink ink. Observations with a microscope indicate that, although homogenous in texture, the ink is composed of tonalities of different colors: ones entirely black and others black–green and iridescent (these last ones are suggestive of contamination by pyrite). For this reason, both components have been analyzed. The microanalyses have been carried out using two X-rays techniques: one based on energy-dispersive X-rays (EDAX) generated by scanning electronic microscopy and the other based on total reflection (this one of great sensitivity). The techniques provide complementary information. EDAX data have been obtained with a new XL-30 Zaphire apparatus connected to a SEM Philips XL30 microscope and total reflection data with an AXIAL IBM-PC V3.00. X-rays were gathered for optimal angles. Results The analytical results are shown in Tables 1 and 2. The sum of the average percentage of three elements, C, O, and Na, is ∼90% (Table 1). The remaining 10% can be more accurately obtained by multiplying the percentages of inorganic elements from Table 2 by 0.1. Thus, the most probable composition for the Parker ink is 60% C; 25% O; 5% Na; 8% S; 0.7% K; 0.8% Ca; and 0.2% Fe. If we consider (from the percentage of sulfur) that the percentage of inorganic oxygen (as sulfate) is 16% and that the total oxygen percentage is 25%, the percentage of organic oxygen would be 9%. As the C:O ratio in organic compounds is 1.3:1, the percentage of carbon deduced from the percentage of organic oxygen would be 12%. Consequently, the free carbon content should be 48%. On the other hand, for bituminous compounds, 9% of C corresponds to 23% of global matter. Therefore a reasonable proposal on the composition of the Parker Quink ink is the following: • 48% carbon in the elementary state • 23% bituminous or resinous organic compounds with high carbon content
that have contents of this chemical species greater than 15% in weight (on the dry basis). The low ferrous sulfate content in the ink makes it less susceptible to deterioration by conversion to pyrite and therefore, little decay is anticipated. The composition obtained for the black Parker ink (with an evident lack of phosphorus) is also not similar to Chinese ink (Table 4), which is rich in phosphates from the fish glue. Table 1. Elemental Composition of the Black Parker Quink Ink Color
C
O
Na
S
K
Fe
Black
61.94
24.55
4.71
8.53
0.12
0.15
Green
58.73
26.00
5.22
9.67
0.22
0.17
NOTE: Data determined by EDAX-SEM. The results are in weight percentage.
Table 2. Inorganic Element Composition of the Black Parker Quink Ink Color Black
S
K
Ca
Mn
Fe
Ni
Cu
Zn
NOTE: Data determined by total X-ray reflection. The results are in weight percentage.
Table 3. Composition of the Typical Calligraphic Gallotannate Inks Component
Weight (%)
a b Aleppo galls , gall-nuts, tannic acid and/or gallic acidc
40–60
Ferrous sulfate (FeSO4 ⭈7H2 O)
15–20
d
10–15
Arabic gum
Indigoe (logwood) or soluble blue
2– 4
Potassium dichromate/Potasssium aluminum sulfatef
2
Phenol/Boric acid
2
a
An excrescence on Quercus lusitanica, Lamarck (Quercus infectoria, Olivier), caused by the punctures and deposited ova of Cynips Gallae tinctoriae, Olivier (or Diplolepis gallae tinctoriae, of Geoffroy), an hymenopter indigenous to the country from the Bosporus to Syria, and from the Archipelago to the frontier of Persia. b Extracted from fermented c plant galls with water-saturated ether. Product of the hydrolysis of tannic acid, it will produce a purer black color in reaction with iron(II) sulfate, while gallotannic acid produces a comparative browner pigment. dA water soluble golden-colored sap collected from Acacia trees (Acacia senegal). eObtained from the wood of the campeachy tree. Boiled in tap water, it creates a blood-red solution, although it will shift to blue in alkaline solutions and to yellow–orange in highly acidic solutions. f Chemicals with presumable stabilizing properties for the ink.
Table 4. Black Chinese Ink Composition Component
• 7% calcium sulfate
Carbon black (from soot)
25–33
• 4% potassium sulfate
Fish glue
66–75
• 1% iron(II) sulfate
Indigo
1
Camphor
1
The first conclusion that can be obtained from this composition is that the Parker Quink ink, although rich in sulfates, is poor in iron(II) sulfate. This feature differentiates it from the composition of typical gallotannate inks (Table 3) www.JCE.DivCHED.org
•
—
Green 84.68 5.12 7.44 0.37 1.38 0.22 0.18 0.16 0.44
• 16% sodium sulfate
• 1% mineral species (not characterized) containing Ni, Cr, Cu, and Zn
Cr
78.21 8.70 9.46 0.27 2.44 0.29 0.26 0.36
Weight (%)
NOTE: The black soot is produced by the imperfect combustion of pitch resin, or fatty substances, such as naphthalene, in a vessel within a tent made of sheepskin or paper. The smoke is deposited on the inside of the tent which is then beaten to cause the soot to fall off. The soot is then heated several times to a very high temperature in a metal container having small opening in the top, through which the impurities escape.
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On the other hand, the comparison of the Parker ink composition with the printing ink composition (Table 5), referred in 1875 by Rafael Sáez y Palacios (6) (according to French chemist Henri Braconnot; ref 7 ), led us to observe important similarities, although admitting the following differences: • Although the raw materials are similar for both the Parker fountain pen ink and the printing ink, the degree of pyrolysis is smaller for the former since the percentage of carbon in the elementary state is higher in the latter. • Sodium sulfate can perform the same function in the Parker fountain pen ink as the ammonium sulfate in the printing ink.
Other conclusions can be obtained from the composition for Parker Quink ink. Since the deliberate addition of potassium sulfate to any of the two varieties of fountain pen ink seems improbable and since the quantity of potassium dichromate in the green-colored variety is low, it seems reasonable to postulate a vegetal origin for the potassium ion. We believe that such vegetal origin for the potassium ion comes from logwood or indigo. Carbon black and indigo have the advantage of imparting a preservative effect to the ink. Discussion As a result of the low iron(II) sulfate content, we can conclude that the Parker Quink ink will be relatively stable on documents, in suitable conditions, and thus will provide longevity (8–10). However, documents written with this ink are partially erased by water immersion and almost totally erased when minimum quantities of nonbiological detergent are added to the water. The vendor was asked to give an explanation regarding this observation (11): Parker inks are not designed to meet the specialist requirements laid down for inks intended for use in Official registers [and that the term] permanent [is to indicate that the ink] although water-based, contains dyes that have no great affinity with paper, cotton, wool or any absorbent material [and that] when subjected to water immersion the soluble dye is washed away, leaving a legible permanent trace.
Tests of stability with respect to water immersion with similar inks resulted in similar conclusions, although Pelikan 4001 and Cross inks are more indelible (11). With respect to the comparison established between the Parker Quink ink and old press ink, it is necessary to point out that their analogies are greater than their differences only on the dry basis. However in suspension the press inks are greasier and more gelatinous than those of writing inks, and the sticky character of those (inspired by the ink used in Biro’s ballpoint pen) contrasts with the fluidity that ethylene glycol
Table 5. Chemical Composition of the Powders Used in the Traditional Printing Inks Powders
Weight (%)
Carbon
79.4
Resins and bitumen
5.3 + 1.7
(NH4)2SO4
3.3
K2SO4
0.4
CaSO4
0.8
(Fe,Ca)3(PO4)2
0.3
SiO2
0.6
H2O
8
Others
0.5
Note: Data according to Braconnot (7). Ulmine and unidentified species are included in the "others".
confers to the fountain pens. The new printers’ inks, primarily those for house or office printers, tend to differ more from the writing inks and only in rare cases are they analogous: for example, the Parker Quink ink is compatible with the ink used in the cartridges of the printing HP Portable DeskJet. Such similarities suggests a forward monitoring of writings printed with this type of ink-jet. Finally, the microbiological study of the inks has shown that the addition of phenols is not sufficient to prevent colonization by bacteria and mold. This article achieves the aim of exposing undergraduate students to the world of printing and publishing. Science students will gain an insight into the materials and process of ink production. On the other hand, students in creative disciplines who are interested in the conservation of documents will learn about the necessity of securing the longevity of writings and drawings created with computer printers. Literature Cited 1. Nir-El, Y.; Broshi, M. Dead Sea Discoveries 1996, 3, 157–167. 2. Halliwell, B.; Gutteridge, J. M. C. Biochem. J. 1984, 219, 1–14. 3. García-Guinea, J.; Martínez-Frías, J.; González-Martín, R.; Zamora, L. Nature 1997, 388, 631. 4. Kim, S. D.; Kilbane, J. J.; Cha, D. K. Eniron. Eng. Sci. 1999, 16, 139–145. 5. Buquet, A. Int. Criminal Police Rev. 1982, 362, 237. 6. Sáez y Palacios, R. Tratado de Química Inorgánica Teórico y Práctico; Carlos Bailly-Bailliere: Madrid, 1875. 7. Braconnot, H. http://www.cyberlipid.org/chevreul/braconnot.htm (accessed Jun 2006). 8. Cantu, A. A. J. Foren. Sci. 1988, 33, 744. 9. Fryd, C. F. M. Med. Sci. Law 1974, 14, 87. 10. Patterson, D. J. Foren. Sci. Soc. UK 1964, 4, 200. 11. Friend, A. Wessex LMCs Bulletin 2000, Sept. http:// www.dgitservices.co.uk/wessexlmcs/bullarch/sep00bull/ sep00bull.html (accessed Jun 2006).
The structures of a number of the molecules discussed in this article are available in fully manipulable Jmol and Chime format as JCE Featured Molecules in JCE Online (see page 1568).
Featured Molecules
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