Blue scales

Comparative studies show the considerable impact attributed to the medium. Certain types of fat dyes, for instance, have lightfastness equal to step 8 on the ISO Scale (Blue Scale) if they are incorporated in polystyrene or similar polymers, while in other media their lightfastness drops to step 1 or 2. 

As an example, a given pigment, incorporated in one medium, may match grade 8 on the Blue Scale for lightfastness, which is an excellent value while a change of application medium may render the same pigment sensitive enough to reach only... 

P.Y.97 is very lightfast and durable in this respect it excels over P.Y.l, especially in white reductions. In a variety of systems (air drying and baking paints), P.Y.97 exhibits a lightfastness wich corresponds to step 6-7 on the Blue Scale, even if it is reduced by as much as 1 140 Ti02. 

P.Y.116 is also used in plastics. In plasticized PVC, it shows little tendency to bleed and is thermally stable up to 180°C. The lightfastness of transparent PVC colorations (0.1% pigment) equals step 7-8 in 1/3 SD (with 5% TiOz), it corresponds to step 6 on the Blue Scale. Insufficient heat resistance limits the application of P.Y.116 in polyolefins, polystyrene, and other polymers which are processed at high temperature. 

P.Y.183 is bleed resistant in plasticized PVC, where its poor tinctorial strength is of some disadvantage. 1/3 SD samples (5% TiOz) require 1.64% pigment. Such systems provide a lightfastness which is equal to step 6 on the Blue Scale 1/3 SD transparent colorations correspond to step 6-7 on the Blue Scale. 

The paint industry shows little interest in P.Y.12, since it is not sufficiently fast to overcoating for use in baking enamels. In air drying paints, lightfastness of P.Y.12 in white reduction (with 1 5 TiOz) only equals step 2 on the Blue Scale. 

At equal depth of shade, the lightfastness of P.Y.13 exceeds that of similarly transparent types of P.Y.12 by one to two steps on the Blue Scale. 

The paint industry shows only limited interest in either P.Y.13 or 12. Although the redder varieties of P.Y.13 are more lightfast than the P.Y.12 types by a few steps on the Blue Scale, they do not reach the lightfastness of Hansa Yellow type monoazo pigments. P.Y.13 is not fast to overpainting. 

P.Y.12 and considerably more so in comparison with P.Y.13. A number of the P.Y.14 types are appreciably greener than the standard yellow on the European Scale. P.Y.14 is not only weaker than comparable P.Y.13 varieties with similar physical characteristics, such as specific surface area but it is also less lightfast by 1 to 2 steps on the Blue Scale. Its resistance to solvents is also comparatively poor. This somewhat limits its use for process inks in offset and letterpress application to special cases, which is equally true for P.Y.14 blends with reddish pigments. Types with fine particle sizes, which match highly transparent versions of P.Y.12 and 13, are not available in Europe. 

The textiles printing industry has an appreciable interest in P.Y.17 and applies it in the form of pigment preparations. Where its fastness properties satisfy the specifications and where the use requirements are not too demanding, the pigment is also utilized for spin dyeing purposes. Manufacturer recommendations include media such as polyacrylonitrile and cellulose acetate fibers, on which 1/3 SD pigment prints exhibit a lightfastness which is equal to step 5 on the Blue Scale. 

P. Y.90 has little commercial impact, it is a regional product. The pigment provides very reddish yellow shades, similar to those of the much lightfaster P.Y.l 14.1/1 SD and 1/3 SD letterpress proof prints equal only step 3 on the Blue Scale, while corresponding P.Y.114 specimens reach step 4-5 and 4, respectively. 

P.Y.114 affords very reddish yellow shades which closely resemble those of P.Y.83, although the level of the fastness properties of P.Y.l 14 is lower it is somewhere between those of P.Y.12 and 13. In print, P.Y.114 is less lightfast than P.Y.83 the difference is 1/2 to 2 steps on the Blue Scale, depending on the depth of shade but P.Y.114 does not achieve the tinctorial strength of P.Y.83. 

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