Blue Dyes

This section provides background information on dyes for cotton that I have examined as alternatives to "Phthalogen Blue" . This is a brilliant, permanent blue that attracts biting flies. Although some phthalogen dyestuffs (IF3GM, IF3GK, IBN) are still used for specific applications (Miles, 2003), these historical Ingrain dyes for cotton developed by Bayer in the 1950's are now rarely used for solid-shade dyeing. Hence, genuine phthalogen blue cloth for traps is extremely difficult to obtain.

After testing various dyes, I have found only one type of reactive dye that can serve as a practical substitute for phthalogen blue. Traps dyed a DARK greenish-blue = turquoise with reactive dyes such as Procion Turquoise M-G (there are many options) perform as well or better than  traps dyed phthalogen blue. These CuPc-based reactive dyes contain sulphonated chromophores (Miles, 2003) and are likely mixtures of several compounds (Paula Burch). Conneely et al. (1999) state that Remazol Turquoise G is tetrasulphonated with one or two modified sulphonate groups. None of the structures of the CuPc-based reactive dyes were listed in the last paper edition of the Colour Index. Osugi et al. (2003) have recently demonstrated that Reactive Blue 15 or Cibacron Turquoise FGF-P is a tetra-sulphonated CuPc dye (PDF). Meng et al. (2005) contains new information, but I have not seen this publication.

The two CuPc-based reactive dyes I have worked with maintain brilliance for a useful period of time, but will fade much faster than ingrain or vat dyes (Weathering of Fabrics). Some other examples of typical reactive dyes available to the consumer based on CuPc are Remazol Turquoise G (Reactive Blue 21) and Procion Turquoise H-A (Reactive Blue 71). These are available from Pro Chemical & Dye under the codes H-A and LR410 as turquoise dyes. See Paula Burch's web site for information on other suppliers of dyes to consumers as there are several other options.

High-performance dyes with multiple reactive groups are used in industrial dyeing (requiring higher temperatures), but are not available nor practical, for the consumer. It may be possible to dye turquoise-fabrics with better weathering properties, but this seems to still be an elusive target (Gorenšek & Sedeljšak, 2000).

Taylor, J.A. (2000) Recent developments in reactive dyes. Review of Progress in Coloration 30, 93-107.

I have a basic interest in phthalogen blue dyes, both the ingrain dyes and the many metal phthalocyanine dyes, reactive or otherwise, that produce deep, brilliant blue or greenish-blue colours on any fabric, not just cotton. I'd be happy to exchange reference samples to learn more about what is being used around the world to produce these specific colours.

 Contact me at smihok@rogers.com.

Practical Blue Dyes
Colours & Chemical Structures
Industrial Dyeing
CuPc - C.I. Pigment Blue 15
Phthalogen Blue Cottons
Colour Comparisons
Home Dyeing
CuPc Reactive Dyes
References

 Note that the swatches displayed on a computer monitor are not able
to reproduce subtle differences in colour

For an introduction to dyeing and many useful links see Paula Burch's Dyeing web site. Pro Chemical & Dye is a convenient source of dyes and auxiliaries in North America; this company also provides practical instructions on how to use reactive dyes. Many reactive dyes are no longer under patent, and hence there are many retail sources around the world.

The Society of Dyers and Colorists (SDC) in the UK is a good source for reference books (e.g. Ingamells (1993) for a simple overview, and Shore (1995) and similar recent books for a detailed technical treatment). Along with the American Association of Textile Chemists and Colorists, the SDC produces the authoritative reference on dyes, the Colour Index International, now in its 4th edition. This key electronic reference is hard to obtain, but the third edition can be found in major academic libraries. What I present here has been assembled from the third edition (1971) and its updates to Volume 9 in 1987, and from diverse textbooks.

For anyone interested in the forensic identification of dyes in textiles, there is an excellent treatment of this topic in Robertson & Grieve (1999). Practical information is also available in a major publication produced in 1999 by the FBI Forensic Fiber Examination Guidelines.

Although definitive  identification of dyes can be a daunting task requiring sophisticated procedures, some simple and practical tests are also informative. For example, excellent light fastness and resistance to chlorine bleach can help differentiate properly-dyed phthalogen blue cloth from many other blue fabrics (Salvin, 1968). Resin-bonded phthalogen blue fabrics can also be differentiated from ingrain-dyed fabrics by  examination of the fabric if one teases out the fibres (see Weaves for examples). Resin-bonded fabrics show only surface colouration, with poor penetration where fibres cross. Fabrics dyed with ingrain dyes (but also reactive, vat,  etc. dyes) have uniform, deep coloration throughout all fibres. There are many simple tests like this that can be done with minimal fuss (Salvin, 1968).

Direct Blue 86
Typical Industrial Turquoise Blue Dye

[HOT dyeing, 95 °C]

Two samples of blue cotton I obtained from Nairobi in 2003 were crudely similar to phthalogen blue,  but were clearly not dyed with phthalogen blue IF3GM. I tested these samples outdoors for colour fastness; they both faded badly after only a few months. From their reflectance spectra, and fading properties, I think reactive dyes were used, most likely a combination of triphenodioxazine and anthraquinone dyes. These recent fabrics are close to phthalogen blue,  but are duller and more royal blue when compared with genuine phthalogen blue IF3GM reference fabrics. A similar sample I obtained in 2006 was a better colour match but was also not genuine phthalogen blue IF3GM.

Home Dyeing

Practical Advice from a "Novice Dyer"

These dark shades were produced on heavy-weight, natural (unbleached) cotton with a twill weave to obtain an opaque, textured fabric similar to the cotton "drill" fabrics used for tsetse traps in Africa (e.g. 200 ±  30 grams per square metre, or about an 8-10 oz bull denim fabric weight).

For examples of fabrics that are sold for home dyeing, see the extensive list at Dharma Trading. The "Mid-weight cotton twill denim PFD" is an excellent choice,  better than the specific bull denim  I used here. I have dyed samples of about 40 Dharma fabrics with Procion Blue H-EGN and Procion Turquoise M-G to test suitability. There are many good choices in duck/canvas and denim; similar weight tencel also dyes well, but is expensive. The same can be said about hemp/cotton. Finer "quilting" cottons are not opaque, even with high thread counts. The mercerized fabrics take up dye very well, but are more expensive. Rayon, linen and viscose fabrics all tend to have a bit of a sheen and are not suitable for traps. Altogether, an 8-10 oz. cotton twill denim (properly washed and scoured) remains a logical and economical choice.

A 3.5 to 4 yard length of 62-inch width bull denim (plan for 10+% shrinkage) can be dyed with a 2 oz. bottle (or less) of reactive dye (dry powder, by weight) to make enough deep blue fabric for three Nzi traps. This amount of fabric weighs about 2.5 pounds, or slightly more than 1 kilogram. For practical recipes on how to dye a "dark shade" in a either a tub or in a washing machine, see the instructions provided by Prochemical and Dye for reactive dyes. I more or less follow Prochem's instructions, but use longer times to ensure depth of shade (30 minutes in the dye bath, and 90 minutes in the fixative).

As an example - on the minimum setting on an Amana Model LWC80AW home washing machine, I can dye in a volume of 40 liters. Other machines might allow for a more practical, lower volume. To produce most of the colours here, I have been working at 5% dye owg (on weight of goods), and at about 4-5% salt concentration (a 1.5-2 kg bag of grocery store pickling salt). I have been using between 150-200 g of soda ash as a fixative ("pH up" at pool stores, but confirm that it is actually soda ash!). Temperature drops about 10 degrees when water is added as the tub heats up.  With a good home hot water heater, one can easily dye at a starting temperature of 55-60 degrees, when required for dyes like Remazol or the Turquoise dyes. Temperature falls about 10 degrees by the end of dyeing.

There are many possible variations on temperature, timing, dye and salt concentration, pH, etc., but one can get excellent results following the basic instructions provided by Prochem. More economical dyeing (e.g. at 3-4% owg) is possible if more cloth is dyed in a smaller volume of water, i.e. if one uses a lower liquor-to-goods ratio of about 1:10 or 1:20, and with better temperature control.

For dyes requiring very hot water (Procion H series, Direct Blue 86), and/or more difficult procedures (vat Dyes), a washing machine cannot be used. To do this type of dyeing by hand, use large stainless steel or enamel "stock pots" / "canning pots" / "brewing kettles" - taking proper precautions for the temperatures and types of solutions being handled. Note that aluminum, copper, iron, etc. pots cannot be used as they interfere with the chemistry. There is a tremendous amount of practical advice on the web.

The Turquoise dyes based on copper phthalocyanine special attention  to obtain brilliant and fast colours in a deep shade. These results are for dye at about 5% owg and a 1:20 liquor ratio.

Use a high concentration of glauber's salt (7-10%), and a high temperature (50-60 °C) in the dye bath (30 min), and extended fixation (90 min). Even higher temperatures may aid fixation, but I have yet to test this.  Do not skimp on the salt as large amounts are critical for deep shades!  Use a "high" concentration of soda ash with gradual additions over 15 minutes (0.83% on final volume); the amounts recommended by Prochemical and Dye for dark shades are about right. Dyeing a large quantity of fabric in a washing machine is quite practical and produces acceptable results.

Post-treatment of CuPc-based reactive dyes with ultraviolet blocking agents may  improve light fastness, given promising results reported by Batchelor et al. (2003) for two dyes in this class. RIT® Sun-Guard™ belongs to this class of uv agents and is available to consumers. I have tested it once as a protectant for two CuPc-based reactive dyes, but noticed no difference in fading properties.

Weathering properties are shown in the table below for fabrics placed outdoors during summer in Russell, Ontario. Swatches were vertical with the twill weave facing west for maximum exposure to afternoon sun (how a trap is typically set). Many more examples for various dyes and fabrics are in Weathering of Fabrics. That section also includes a listing of light fastness ratings for most of the dyes listed on this page.

Results were similar with both the Cibacron (= Sabracon in the Prochemical and Dye catalogue) and Procion turquoise dyes. Colour was retained moderately well in the first month, faded noticeably in the second month, and faded considerably by the end of three months. Traps made from these fabrics performed well for as long as experiments continued, even with moderate fading. Both dyes are likely suitable for experimental work, so long as one uses traps for only a few months.

Cibacron dyes are now made by Huntsman following purchase of the Ciba business unit in 2006. The Cibacron dyes were renamed "NOVACRON" in 2007.

For a useful technical discussion, see the paper below. It can be downloaded as a PDF.

Hehlen, M. (1991) Effects of dye substantivity in dyeing cotton with reactive dyes. American Association of Textile Colorists and Chemists Review, November, 21-27.

References

Batchelor, S.N., Carr, D., Coleman, C.E., Fairclough, L. & Jarvis, A. (2003) The photofading mechanism of commercial reactive dyes on cotton. Dyes and Pigments 59, 269-273.

Christie, R.M. (2001) Colour Chemistry. Cambridge, UK: The Royal Society of Chemistry.

Hunger, K. (2003) Industrial dyes. Weinheim: Wiley-VCH.

Ingamells, W. (1993) Colour for textiles. A user's handbook. Bradford, UK: Society of Dyers and Colourists.

Kadish, K.M., Smith K.M. &  Guilard R. (2003) The porphyrin handbook. Volume 19. Applications of phthalocyanines. Amsterdam: Academic Press.

Loebbert, G. (1996) Phthalocyanine compounds. Kirk-Othmer Encyclopedia of Chemical Technology, Volume 18, Fourth Edition 18, 1043-1058.

Moser, F.H. & Thomas F.H. (1983) The Phthalocyanines. Volume II. Manufacture and applications. Boca Raton, Florida: CRC Press.

Robertson, J. & Grieve M. (1999) Forensic examination of fibres. London: Taylor & Francis.

SDC & AATCC. (1971) Colour Index, Third edition. Bradford, UK: Society of Dyers and Colourists & American Association of Textile Chemists and Colorists.

Osugi, M.E., Carneiro, P.A. & Zanoni, V.B. (2003) Determination of phthalocyanine textile dye, reactive turquoise blue, by electrochemical techniques. Journal of the Brazilian Chemical Society, 14, 660-665.

Salvin, V.S. (1968) Identification of dye classes on fibers. pp. 187-218 in American Association of Textile Chemists and Colorists. (Ed) Analytical methods for a textile laboratory, second edition, AATCC Monograph Number 3. Research Triangle Park, North Carolina, American Association of Textile Chemists and Colorists.

Shore, J. (1995) Cellulosics dyeing. Bradford, UK: Society of Dyers and Colourists

Smith, H.M. (1988) Phthalocyanine blue pigments. pp. 663-674 in Lewis, P.A. (Ed) Pigment Handbook. Volume 1. Properties and economics, Second edition.  New York, John Wiley & Sons.

Smith, R.E. (1993) Dyes, reactive. pp. 809-838 in Kirtk-Othmer. (Ed) Encyclopedia of chemical technology, Volume 8, Fourth edition.  New York, John Wiley & Sons.

Vollmann, H. (1971) Phthalogen dyestuffs, Chapter V. pp. 283-311 in Venkataraman, K. (Ed) The chemistry of synthetic dyes, Volume V.  New York, Academic Press.