Tests for light fastness

Press, Volume CXI, Issue 32706, 8 September 1971, Page 13

Tests for light fastness

A recent arrival at the Wool Board’s laboratory in Wellington is a machine which is accepted as the international standard for testing the light fastness of materials.

The ability of a materia! to retain its colour well in sunlight is one of the requirements for approval to market that material under the Woolmark label. As the Wool Board has the responsibility for testing all fabrics submitted for the Woolmark seal, it has become essential for it to have the machinery necessary to make a standard test which gives a widely accepted scale of results. The new machine, a Ger-

man-made Xenotest 150, uses a Xenon arc light to subject the materials being tested to completely uniform and reproducible light and weather conditions.

Samples of the fabrics are placed in an atmosphere which is strictly controlled for light intensity, heat and humidity. The duration of the exposure varies with the severity of the test being applied, but in general 30 hours under the light gives an accurate assessment of the light fastness of the material. A period of 24 hours in the

Xenotest 150 is roughly equivalent to 10 days in the open air in average weather conditions.

Testing for light fastness is not new, of course, but the new machine is quicker and gives a more accurate result than the arc lights used for the test until now.

One big advantage for the manufacturer whose products come through the test is that the machine gives results which are standard throughout the world, and which are recognised internationally in arbitration. The machine is a versatile one, and although it has so far been used only in testing for Woolmark applications, it is equally useful in giving colour-fastness readings for ink, paint, paper, rubber and plastic materials. The Wool Board intends making the machine available to any wool user who strikes a colour-fastness problem or who needs a weathering test made at any stage of development of a product.