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Hi Allan.
Permanence is always relative. Considerations for "what's best" are subjective to the individual painter's situation. It wouldn't do to construct a temporary job shack on a construction site out of dry-set granite blocks.
The prime criterion for "student grade" paint is low cost. The quality of all components in student grades is adjusted to be economical. Fillers and extenders are cheaper than pigment stuffs. Not all pigments of similar color cost the same, nor do they perform the same. Since reasonable folks don't expect student work to endure for posterity to "enjoy" (?!?) permanence at that tier is the last consideration. Professional painters should use the highest quality paint and materials available to them. As they have an obligation to deliver quality to their clients, they should not use student colors.
"Permanence A" is no doubt W&N's in-house system of quality standards. Where artists' oil colors are concerned, ASTM standards are subjective enough without having to deal with arbitrary standards set by individual manufacturers.
The W&N color you have, "Permanent Crimson Lake" is a convenience mix of anthraquinoid (red) and ultramarine (blue). It is not a "lake". No doubt the anthraquinoid red employed is too "hot" to approximate what most folks expect in alizarine crimson, so it's been "cooled down" with the admixture of ultramarine.
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