Weathering of Fabrics

This section provides examples of how selected fabrics weather outdoors in a temperate northern climate at Russell, Ontario, Canada (45° 15' N, 75 21' W, 74 m asl). The fabrics were suspended vertically facing ~ west into the mid-afternoon sun. A western exposure was chosen to mimic the way a Nzi trap is normally set in the north. Technical details on these fabrics are in Fabrics, Blue Fabrics and Blue Dyes.

"SAFE" FABRICS

Top Notch marine polyester canvas and Sunbrella acrylic marine / awning canvas are "safe" - they are both extremely colour fast and are readily-available either retail or by mail order. Top Notch Blue and Sunbrella Pacific Blue are recommended as suitable alternatives to Phthalogen Blue cotton. Seconds also appear to be suitable, although I have only tested their weathering properties for two seasons to date.

Light Fastness of Blue Dyes

Light fastness is only one aspect of colour fading, but is probably the most important one. It is typically measured under defined conditions with a xenon arc lamp and expressed on a scale of 1 to 8; eight is the highest rating (excellent). An example of a basic standard is the ISO scale for eight blue dyeings on wool.  Each level requires twice the exposure time of the one below to cause the same degree of fading. Technical details are explained in the following publication:

Pugh, S.L. & Guthrie, J.T. (2001) The development of light fastness testing and light fastness standards. Review of Progress in Coloration 31, 42-56.

Deep shades normally fade at a slower rate than light shades. Light fastness ratings are therefore expressed relative to the closest match to six standard depths. In the ISO standard, these are defined for 20 reference colours  at depths of 2/1, 1/1, 1/3, 1/6, 1/12 and 1/25 (Ingamells, 1993).

A light fastness rating of 7-8 is recommended for  "permanent" traps. Performance should also be tested under real-world conditions of heat, moisture, wind, etc. Direct Blue 86, and Remazol Brilliant Blue R faded considerably outdoors, despite a rating of 7.

I have only been able to scratch the surface of what is possible in researching dyes as I have only been able to test dyes in the public domain, well after patents have expired.  An example of recent developments in dye research is:

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.

This recent paper discusses two useful phthalocyanine reactive dyes I have not tested. These are available to the consumer from Pro Chemical & Dye in the USA.

Procion Turquoise H-A (RB 71) - Pro Chemical H-A Turquoise
Remazol Turquoise G (RB 21) - Pro Chemical LR410 Turquoise 50%

Post-treatment of CuPc-based reactive dyes with an ultraviolet blocking agent may improve light fastness, given the excellent results achieved with application of 1% Tinuvin™ 571 (Batchelor et al., 2003). For the consumer, there is a credible home product that may be useful in this context (RIT® Sun-Guard™). In 2006, I  tested fading of fabric treated with this product for  two CuPc-based reactive dyes. Unfortunately, there was no difference in the rate of fading with treatment.