The smallest category of the seven, tanning involves the darkening of comic paper through exposure to the elements. Interaction with the environment and chemical reactions within the paper results in a comic turning brown and brittle over time. Page tanning is considered an aesthetic defect, but brittleness is classified as a structural defect due to its effect on how the comic holds together. Tanning and brittleness typically begin around the edges of a comic book and work their way towards the middle over time. Sometimes only part of a comic is exposed to the elements, like a corner protruding from a large stack, which can cause localized tanning and brittleness.
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Types:
Tanning refers to the darkening of comic book paper, primarily affecting the cover due to oxidation, with the edges and spine most commonly affected. This occurs because of limited oxygen exposure to stacked comics' outer edges and contact between the inside cover and acidic interior pages, accelerating oxidation. Tanning ranges from minor edge discoloration to full cover darkening, often accompanied by brittleness. The impact on grade varies based on shade, area affected and overall grade, with very light tanning acceptable in high grades. Moderate tanning may lower grades to 8.0-9.0, while heavy tanning can drop them to 6.0 and extreme cases to 4.0-5.0. Dell comics from the '50s and '60s exhibit tanning more frequently due to paper type and are graded less harshly for inside cover tanning. Tanning is less prevalent in comics past the '70s and nearly absent in newer ones due to changes in paper composition.