By teasing out the fabric, the quality of dyeing is usually obvious from the uniformity and depth of shade in the bundles of fibres of the warp and the weft. Unfortunately, different classes and mixtures of dyes can produce similar colours. These cannot always be readily identified without chemical tests (compare the examples of vat, reactive, and direct dyes to cloth dyed phthalogen blue). It is also difficult to identify individual dyes without employing sophisticated analytical techniques. However, some simple tests, e.g. reactions to chlorine bleach, reducing agents, etc. are easy to perform. This can narrow down what might have been done, especially for blue dyes (forensics).

When colour is mainly on the surface of the fibre, and is nearly absent where fibres cross, this implies the application of pigment with a resin-bonding process. This is more typical of printed fabrics with complex surface designs; it is unusual for solid-shade dyeing. However, this appears to be how "phthalogen blue" fabrics were produced by the Awassa Textile Factory in Ethiopia in the mid 1990s.

Phthalogen Blue IF3GM Cotton Drill, custom-dyed for experimental studies
Mount Kenya Textiles, Kenya - excellent deep dyeing, excellent light-fastness and extremely resistant to chlorine bleach;, used as a standard for many fabric comparisons

Economical "Jinja" cotton, often used for mass production of traps in East Africa
Retail market, Kenya - almost surely Phthalogen Blue IF3GM dyeing based on the colour spectrum and high quality of the dyeing, plain weave

Cotton Drill used in tsetse traps in central and southern Africa
Bonar Industries, Zimbabwe - almost surely Phthalogen Blue IF3GM dyeing based on the colour spectrum and high quality of the dyeing

Cotton Drill used for large-scale production of tsetse traps in Ethiopia
Awassa Textile Factory, Ethiopia - undisclosed process with minor spectral differences relative to phthalogen blue IF3GM; poor penetration of dye into the fibre with white spots where the fibres cross; poor light-fastness, readily stripped with chlorine bleach

Imitation Phthalogen Blue - a simple mix of two reactive dyes on plain cotton
This was produced by combining a sulphonated copper phthalocyanine and an anthraquinone reactive dye to produce a nearly perfect match to Ethiopian phthalogen blue cloth. This shows how difficult it can be to discern how cloth has been dyed without tests of light fastness, bleach fastness, etc. to differentiate underlying processes.

"Santiago" Polyester / Cotton widely-used in tsetse traps in West Africa
Les Établissements Robert Gonfreville, Bouaké, Ivory Coast - undisclosed process; a very good colour match to phthalogen blue IF3GM cotton with good light-fastness; phthalogen blue IF3GM can be used to dye the cotton fibres, followed by a disperse dye for the polyester fibres , but there are many possibilities; some evidence of poor dye penetration,

NOTE the sheen that is evident on ALL of the following synthetic fibres versus cotton

Matt Blue 100% Polyester "Pongee 2" VF #10 - 1995 Code T7841005, made in Taiwan
Vestergaard Frandsen, Denmark - undisclosed processes, likely dyed with several azo or anthraquinone disperse dyes to produce an approximate match to phthalogen blue

"New blue 286" 100% Polyester - 2003, made in Vietnam
Vestergaard Frandsen, Denmark - undisclosed dyes replacing "Pongee #2"

Sunbrella Pacific Blue acrylic awning fabric
Glen Raven Mills, North Carolina - solution dyed acrylic fibres, almost certainly based on copper phthalocyanine given colour spectrum and superb light fastness

Solar Max® nylon flag / banner cloth in Royal Blue
Dupont, Delaware - a light-fast fabric, it is possible to colour nylon with copper phthalocyanine, but I have not yet found a retail product with an exact match

Vat Blue 6 (chlorinated derivative of indanthrone)
An extremely light-fast dye, a brighter colour than the "denim blue" of indigo

Procion Turquoise M-G or Reactive Blue 140 (sulphonated copper phthalocyanine)
A light-fast dye, essentially a bright greenish blue (turquoise) variant of phthalogen blue

Direct Blue 86 (sulphonated copper phthalocyanine)
A common industrial turquoise dye; it can produce only light shades and is readily stripped by chlorine bleach

Updated
12-Nov-2007