Azo dyes and pigments
Description
A large group of synthetic dyestuffs containing one or more nitrogen double bond (azo) groups as its chromophore. Azo chromophores were first discovered in 1863 when Martius and Lightfoot coupled diazonium ions and amines. Within the year, Peter Greiss prepared Bismarck brown, the first azo dye. By the 1880s numerous other azo dyes, such as para red and primuline red, were developed. Since that time, most modern dyestuffs have been derived from diazotized aromatic amines, and hence are sometimes known as diazo dyes. The simplest azo dyes are yellow, but changing the number of chromophores or the backbone structure can produce red, violet, blue and even black dyes. Azo dyes are used as textile colorants, and well as in industrial paints, printing inks, varnishes, plastics, crayons and other products. In recent years, many high performance azo pigments have been developed that meet the stringent lightfastness requirements required for artwork (Berrie and Lomax 1997).
| Classification |
First developed | Lightfastness | Heat stability | Other properties | Common uses | Azo Pigments most frequently used in traditional artists paints (Berrie and Lomax 1977) |
|---|---|---|---|---|---|---|
| Pyrazolones | 1884 | very good | to 150 C | High transparency and good heat resistance; sensitive to solvents and water. | Paints: architectural, artist Coloring: textiles, rubbers |
PO13 (CI 21110); PY100 (CI 19140) |
| Naphthol Reds | 1911 | very good | to 160 C | Highly resistant to acids, alkalis, and soaps; good tinting strength and inexpensive; poor bleed resistance | Paints: architectural, automobile Coloring: plastics |
PO38 (CI 12367); PR2 (CI 12310); PR5 (CI 12409); PR7 (CI 12420); PR8 (CI 12335); PR9 (CI 12460); PR12 (CI 12385); PR14 (CI 12380); PR17 (CI 12390); PR18 (CI 12350); PR22 (CI 12315); PR23 (CI 12355); PR31 (CI 12360); PR112 (CI 12370); PR119 (CI 12469); PR146 (CI 12485); PR17O (CI 12475); PR187 (CI 12468); PR188 (CI 12467) |
| B-Naphthols | 1895-1911 | very good | to 150 C | Good chemical resistance but poor bleed resistance | Paints: architectural Coloring: plastics, rubbers, chalks, crayons, inks |
PO2 (CI 12060); PRO5 (CI 12075); PRO17 (CI 15510); PR1 (CI 12070); PR3 (CI 12120); PR4 (CI 12085); PR48 (CI 15865); PR49 (CI 15630); PR52 (CI 15860); PR53 (CI 15585); PR57 (CI 15850); PR60 (CI 16105) |
| Arylide (Hansa) Yellows | 1900 | very good | to 150 C | Good lightfastness; resistant to water, oil, acids and bases; but not bleed resistant | Paints: architectural, artist Coloring: chalks, crayons, inks |
PO1 (CI 11725); PY1 (Hansa Yellow G; CI 11680); PY3 (Hansa Yellow 10G; CI 11710); PY4 (CI 11665); PY5 (CI 11660); PY9 (CI 11720); PY65 (CI 11740); PY73 (CI 11738); PY74 (CI 11741); PY75 (CI 11770); PY97 (CI 11767); PY98 (CI 11727) |
| Diarylide Yellows and Oranges | 1911 | poor to good | to 150 C | Primarily used for printing inks, they have twice the tinting strength of the arylides with more bleed resistance | Paints: architectural, artist Coloring: plastics, rubbers, inks |
PY12 (Benzidine Yellow AAA; CI 21090); PY13 (Permanent Yellow GR; CI 21110); PY14 (Benzidine Yellow AAOT; CI 21095); PY17 (Benzidine Yellow AAOA; CI 21105); PY55 (CI 21096); PY81 (CI 21127); PY83 (Permanent Yellow HR; CI 21108); PO14; PO15; PO16 (dianisidine orange) |
| Nickel-azo | 1940 | excellent | good | Expensive but excellent lightfastness, low blend and toxicity; often used in blends with blue to make green | Paints: artist, automobile Coloring: textiles |
PG10 (CI 12775) |
| Disazo condensation pigments | 1957 | very good | to 180 C | Their high molecular increases their lightfastness and decreases their solubility. | Paints: automobile Coloring: plastics, textiles, inks |
|
| Benzimidazolones | 1960 | excellent | >100 C | Outstanding bleed resistance, lightfastness and moderate heat resistance | Paints: artist, automobile Coloring: plastics, chalks, crayons |
PBr25 (CI 12510); PO36 (CI 11780); PO60 (CI 11782); PO62 (CI 11775); PR171 (CI 12512); PR175 (CI 12513); PR176 (CI 12515); PY151 (CI 13980); PY153 (CI 48545); PY154 (CI 11781); PY175 (CI 11784) |
Synonyms and Related Terms
diazo dyes; azo pigments; coal tar colors; ice colors; arylide dyes; Azofarbstoff (Deut.); colorante azoico (Esp.); colorants azoïques (Fr.); colorants azo (Fr.); colorante azoico (It.); corante azo (Port.)
See also Para red, Lithol red, Toluidine red, Tartrazine lake, Hansa pigments, Hansa red, Hansa yellow, Hansa orange
Risks
Some azo dyes are highly toxic and carcinogenic.
Resources and Citations
- B.Berrie, S.Q.Lomax, "Azo Pigments: Their History, Synthesis, Properties and Use in Artists' Materials" in Studies in the History of Art, No.57, National Gallery of Art, Washington DC, 1997.
- Colorants Industry History at colorantshistory.org
- G.S.Brady, Materials Handbook, McGraw-Hill Book Co., New York, 1971 Comment: p. 284
- Ralph Mayer, A Dictionary of Art Terms and Techniques, Harper and Row Publishers, New York, 1969 (also 1945 printing)
- Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
- Hoechst Celanese Corporation, Dictionary of Fiber & Textile Technology (older version called Man-made Fiber and Textile Dictionary, 1965), Hoechst Celanese Corporation, Charlotte NC, 1990
- Van Nostrand's Scientific Encyclopedia, Douglas M. Considine (ed.), Van Nostrand Reinhold, New York, 1976
- Encyclopedia Britannica, http://www.britannica.com Comment: "azo dye" [Accessed April 1, 2002
- Meredith Dorner "Early Dye History And The Introduction of Synthetic Dyes Before The 1870s" -http://www.smith.edu/hsc/silk/Papers/meredith.html
- Thomas B. Brill, Light Its Interaction with Art and Antiquities, Plenum Press, New York City, 1980
- Wikipedia: Azo dye (Accessed Jan. 15, 2006 and May 2025)