Fabrics

FABRICS
Practical advice on materials for making traps
for tsetse and other biting flies

If you don't want to know all the nitty-gritty details...

	Use white, highly transparent, ultraviolet-resistant, polyester mosquito netting, with only a minimal sheen, intended for outdoor use (e.g. Mosquito Curtains standard netting); avoid using dark or very shiny netting.
	Use opaque, well-textured, non-shiny blue fabric that matches the deep, brilliant blue shown below [Phthalogen Blue cotton in the tropics; Pacific Blue # 6001 acrylic awning fabric (Sunbrella) in the north]. Sunbrella has been tested in many areas and works well as a practical substitute for phthalogen blue cotton.
	Use a deep black, opaque fabric such as Sunbrella acrylic or Top Notch polyester. The exact choice of black is not as critical as the choice of blue.
	Choose fabrics designed for outdoor use that will not fade in the sun and rain. Light-fastness is critical; see Weathering of Fabrics for some examples.

The "right stuff" can increase the catch considerably, so it is important to strictly follow this advice. Most convenient retail fabrics such as medium-weight, sportswear polyester / cottons are not suitable for traps as colours will fade badly within a few months.

I have tested "seconds" of Sunbrella (Fabric Warehouse) and Top Notch (Rochford Supply) and they are suitable for traps. The costs of seconds are very reasonable.

I have a basic interest in the phthalogen blue and other metal phthalocyanine dyes that are used to produce deep, brilliant blue or greenish-blue colours on various textiles by various methods. I'd be happy to comment on any fabric samples or exchange reference materials to learn more about what is available on the market around the world.

Contact me at smihok@rogers.com.

Other Practical Options
Detailed instructions for making traps out of other materials are provided at
Making a Plywood Trap

Portable and collapsible painted plywood trap that can be stored flat in winter

Plexiglass trap with an inner wooden frame for permanent, fixed applications

The "Right" colour of BLUE
See Blue Fabrics or Blue Dyes for technical information and other examples

Below is an example of the heavy cotton drill (= bull denim) used in tsetse traps relative to reference phthalogen blue dyeings (Dystar). The blue spectrum of phthalogen blue IF3GM has a single, simple reflectance peak in the middle of the blue region, with low reflectance in the ultraviolet. The twill weave in this fabric produces a rough texture with almost no sheen. At 175 g/m², the cloth is opaque when it is wet or dry, even in bright tropical sunlight.

Kenya drill
Type IF3GM

Dystar Cloth @4%
Type IF3GM

Dystar Thread @4%
Type IF3GK

The colour "Phthalogen Blue" is a generic term for a series of copper and other heavy metal phthalocyanine dyestuffs patented by Bayer in the 1950s. This dyeing process produces exceptionally brilliant and light-fast blues (based on Cu) which can be shifted to blue-greens (Ni) or darker blues (Co) depending on the metal in the dye complex. When CuPc is solubilized (e.g. as in the sulphonated reactive dyes), brilliant turquoise colours result. These turquoise shades are unique in terms of dye chemistry. When CuPc is halogenated as in some paint pigments, "thalo greens" result (e.g. a chlorinated version is Pigment Green 7).

Phthalogen dyes are still sold by Dystar in Germany for printing and dyeing of thread, but are not in common use for solid-shade dyeing of retail fabrics. Nevertheless, suitable phthalogen-dyed fabrics are still available in the tropics, mostly through dyes obtained from Indian chemical manufacturers.

"Phthalogen Brilliant Blue IF3GK and IF3GM" are shown above. The history of the Bayer dyestuffs is outlined in the following publication:

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.

Except for Sunbrella "Pacific Blue", and Top Notch "Blue" this uniquely brilliant blue is difficult to obtain in any fabric outside of the tropics. These marine fabrics are unique with the permanent colour produced through "solution dyeing". In this technique, phthalogen blue pigment is added to the material during polymerization of the synthetic polymer or during the fibre spinning process.

For research purposes, a turquoise variation of phthalogen blue can be obtained by dyeing cotton with Procion Turquoise M-G (Reactive Blue 140), or Cibacron Turquoise F-G, or similar dyes based on sulphonated coppper phthalocyanine. See Blue Dyes if you are interested in dyeing your own cloth.

Colours are typically reproduced poorly by computer monitors. To view Phthalogen Blue, visit an art supply store, and examine a paint that contains ONLY "Pigment Blue 15:1" (e.g. PB15:1) or alpha copper phthalocyanine. An example is Winsor & Newton Finity Artists' Acrylics "Phthalo Blue Red Shade". When mixed with white pigment, "phthalo" paints will produce a close match to Phthalogen Blue cloth. The turquoise colour produced by Procion Turquoise M-G is similar to many cyan inks; it be viewed on a test page from any inkjet or colour laser printer.

There are many forms of copper phthalocyanine (CuPc) and many qualitative terms used in the paint, ink and textile industry for this colour of blue (phthalo blue, peacock blue, royal blue, marine blue, ocean blue, etc.), so always look for the specific pigment (PB 15). Many "phthalo blue" paints are also made from a slightly greenish version of this pigment beta copper phthalocyanine (PB 15:3). The shade difference is subtle and not significant. With simple chemical manipulations, CuPc can also produce brilliant turquoise and cyan colours. Hence, it has major applications in paints, inks and plastics.

Excellent technical information on pigments and the colours they produce is provided by Handprint. Pure pigment powders for experiments can be obtained from stores that supply materials to professional artists, e.g. Stevensons in Canada. You can also view paint colour cards at Winsor & Newton and can download a detailed colour chart in Adobe PDF format. However, it is far better to see colours in person. The retail market is quite diverse.

Although there is no exact match to Phthalogen Blue dyed cotton in printing inks, you can view some reasonable matches by examining Pantone� spot colours. Pantone� 286 is probably the best overall match. Pantone� 293, 2935 and 2945 resemble some of the brighter fabrics. Letraset� Pantone� Tria� marker pens (in art supply stores) are a convenient source for colour examples.

In the tropics, the white polyester mesh used in mosquito bed-nets is usually appropriate for the netting components of the Nzi trap. There are an infinite number of products with various weaves, mesh sizes and fibre types. Purchase only long-lasting, uv-protected materials.

In the north, strong white polyester mosquito netting with a lifespan of five or more seasons can be purchased in modest quantities from Mosquito Curtains. Type IN-06 from Barre Army/Navy is an example of a more economical netting which will last for only about two seasons.

See the sections on Netting and Mesh Sizes for many other practical options.

Insecticide-impregnated netting (synthetic pyrethroids incorporated into polyethylene or polyester) is now also being produced on a very large-scale for bed nets for malaria control (World Health Organisation), but these special materials are not yet readily-available to the consumer. Examples are Olyset �, Permanet � 2.0 and Interceptor �. See the WHO Pesticide Evaluation Scheme (WHOPES) for up-to-date information. This is a rapidly evolving field, with new nets and other products (e.g. ready-made, impregnated clothing) starting to appear on the consumer market (Buzz Off Insect Shield).

The "Nitty-Gritty"

Traps can be made out of many things (not just cloth), but choose alternative materials with caution following the detailed advice provided here.

The choice of the right kind of black fabric may not be critical.

Alternatives to cotton have not been tested extensively, but there appears to be considerable latitude in the use of nylon, polyester, acrylic, or blends for the black component of the trap, even if somewhat shiny. Use of a light-fast synthetic fabric is advantageous, given the poor ability of most retail cottons to retain a deep black colour outdoors for more than 1-2 seasons.

The choice of the right kind of blue fabric is absolutely critical.

Traps made out of shiny blue fabrics (non-texturised synthetics in nylon or polyester, e.g. with smooth textures and a very fine weave) often perform poorly, sometimes extremely poorly.

Nearly all biting flies react best to traps made from heavy-weight, opaque (drill), textured (twill weave), "pure blue" (see swatch above), 100% cotton (fabric used in pants, uniforms, overalls in the tropics).

This blue fabric is easy to obtain in the tropics, but it is not available in the northern hemisphere. The outdoor marine fabrics mentioned earlier are nevertheless good substitutes for genuine phthalogen blue cotton. Some sportswear fabrics may be useful (e.g. a medium-weight, 65% polyester and 35% cotton twill), but it is very difficult to find suitable retail materials in the exact colour of phthalogen blue. These fabrics are nevertheless being produced; e.g. the "Azur" colour produced by TDV Industries, France.

See Blue Dyes for a discussion of more alternatives to phthalogen blue cotton.

Pure synthetics or blends are used by some researchers for both the blue and black components of the trap as they are economical. Synthetics like polyester and nylon also absorb and retain insecticides better than cotton (a major consideration in Africa for control of riverine tsetse).

Some synthetics may be suitable for the black component of the trap, despite being shiny (e.g. 200 Denier Dupont Solar Max^� nylon). More opaque nylon is also available at reasonable cost, e.g. 420 Denier nylon pack cloth, but has to be tested outdoors before use. Some retail nylons fade very badly in the sun as they are not typically intended for prolonged outdoor use.

Synthetics with a smooth texture (shiny) may reduce the catch of biting flies, especially stable flies, horse flies, and savannah species of tsetse.

Always test trap performance and durability before making major commitments.

Non-fabric options (plastic, fibreglass, fibreboard, painted metal or wood) may be appropriate for some flies (particularly Tabanidae or horse flies). Unfortunately, minimal research has been conducted on materials other than cloth to provide generic advice.

Fabric Quality
Colour and texture variation

Blue Fabrics 12k

Large Image (70k)

Fabrics #1 a-c represent variation in Phthalogen Blue IF3GM cottons from Kenya; they only differ in terms of depth of shade.

Fabric #2 is nominal "Phthalogen Blue" cotton from the Awassa Textile Factory, Ethiopia.

Fabric #3 shows the shininess of plastic in "United Nations Blue" from Uniplastics in Nairobi.

Fabrics #4 to 9 are some early experimental 100% polyesters from Vestergaard Frandsen with various textures and shininess.

A final consideration is durability vs cost - relative to expectations of weather, damage by animals, and the very real problem of theft. Always test fabrics under realistic conditions before making major purchases.

When exposed outdoors to sun and rain, many generic retail fabrics fade within a few months. Synthetic netting materials also vary greatly in quality; only ones that contain ultraviolet protectants are suitable for use in traps (e.g. outdoor insect screening).

Practical examples are provided in Fading of Fabrics.

Below is just one example of the colour fastness of two fabrics
used in tsetse traps in East Africa in the 1990s.

Weathering
Weeathered Traps 25k

The trap on the right was made from Ethiopian cotton drill from the Awassa Textile Factory, dyed "Phthalogen Blue". The trap on the left was made from polyester, dyed to a similar colour.

After exposure to high temperatures and bright sunlight in the Rift Valley of Kenya for 2.5 months, the cotton faded considerably. This was either due to poor dyeing or the use of another process (Weaves).

This example illustrates how difficult it is to ensure consistent quality when apparently similar fabrics are obtained from different sources. This Ethiopian cotton was clearly not light-fast, even though "true" phthalogen blue cotton from other sources has excellent light-fastness.