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ACCELERATED FADING Using our LIGHT FASTNESS TESTERS
to evaluate the light fastness of samples to the requirements of BS:1006:1990:UK/TN
Aspects of colour fading with LFTs
Evaluation of the light–fastness of different types of coloured materials is of great importance in many industrial and commercial contexts. Textiles, printed and painted surfaces, coloured plastics, anodised aluminium, paper, and coloured packaging are among the many materials requiring light fastness characteristics to be controlled and for which a simple fading test is required, not only for research but also for quality control purposes during production.
The basic model of MICROSCAL Light Fastness Tester (the LFT1E–500) has been designed to give a simple and economical means of evaluating light–fastness against British Standard Blue Wool Patterns (BS1006:B01), or comparable Standards. The mercury–tungsten MBTL (ML) lamp is mains–operated, consumes only 500 watts, will operate without maintenance for thousands of hours in an apparatus which is fume–free and silent, and which can be accommodated on an ordinary laboratory bench. In its most basic form, the only service required is a mains electricity supply.
There are five types of exposure cells available, two which are not cooled artificially (types B and C), and three of which have provision for being water cooled (types A, AB, and CA). If our Air Cooled Exchanger (ACE) is provided, when cooled exposure cells are being used, the need for a continuously available water supply and drainage can be eliminated.
The benefits of simplicity, reliability, modest capital outlay, and low operating costs combined with close correlation to the fading produced by daylight alone, make the light fastness tester a boon for University Departments and for research laboratories, as well as for works' Standards rooms, warehouses, etc. The basic instrument can also be utilised for the further acceleration of fading tests when using a 'close–frame' adaption. This has provision to deploy up to six of the large rectangular cells (types A, AB, and B).
A separate model (the LFT1E–400) has a different light source (an MB/U mercury lamp) which reduces the unit's electrical power consumption and simultaneously reduces the overall fading time by a factor of 1·6 approximately compared to the LFT1E–500. If required, the 'close–frame' adaption may also be used to accelerate the fading process still further on a smaller number of samples.
Five types of exposure cell
The large rectangular cells have masking plates which permit the exposure of up to ten 1 cm × 5 cm samples per cell. The small cylindrical cells can normally only take one 1 cm × 5 cm sample at a time, although with careful mounting and masking two samples per cell may be accomodated. Three of the cells incorporate water–ways and connection points for simple cooling or temperature moderation as required. The gallery ring of the instrument accepts up to fifty small cells, or a mixture of large and small cells to a limit of twelve large and fourteen small, so that a normal maximum of 134 samples each 1 cm × 5 cm may be exposed in the instrument at one time.
The large cells are supplied with plastics pots into which humidity–control solutions can be introduced in order that the sample environment maintains the chosen relative humidity level. The small cells can have humidity–control solutions placed directly into the bottom of their tubes. Because the humidity in each cell can be controlled independantly, tests can be done at more than one relative humidity level simultaneously. If cooled and un–cooled cells are used at the same time, then differing sample temperatures can also be generated if required.
In the case of the small cylindrical cells (types C and CA), fastness tests of liquids (water colours, oils, and greases, etc.) may also be carried out. |
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