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Storage, care & shipping

What temperature and humidity should comics be stored at?

Published Sep 14, 2026 · Updated Sep 14, 2026 · 1 min read

Short answerCool, dry and stable: a temperature around 18–21 °C (65–70 °F) and relative humidity around 40–50 %, with as little daily swing as possible. Below about 35 % paper becomes brittle; above about 55–60 % mould and foxing become a risk. Heat is the accelerator for every kind of paper decay, so a stable 20 °C beats a room that cycles between 15 °C and 28 °C.

The targets

MeasureAim forAvoid
Temperature18–21 °C, stableOver 24 °C, and daily swings
Relative humidity40–50 %Under 35 % or over 55 %
LightDarkDirect sun and unfiltered fluorescent light

These are the ranges archives and libraries use for paper; comic paper is cheaper than most, so if anything it needs them more.

Why each matters

  • Heat roughly doubles the rate of chemical decay for every 10 °C rise. The difference between an attic and a cool interior room, over decades, is the difference between white and tan pages.
  • High humidity feeds mould, causes the brown spots called foxing, and lets the paper absorb water and ripple.
  • Low humidity dries the paper and makes it brittle — particularly dangerous for Golden Age newsprint.
  • Swings make paper expand and contract, loosening staples and stressing spines.

Measuring and controlling

  • A digital hygrometer with a min/max memory shows what the room actually does across a day and a season.
  • A small dehumidifier or a sealed container with silica gel brings humidity down; a humidifier or a simple bowl of water in the cupboard brings it up in dry winters.
  • Interior rooms and closets are naturally more stable than rooms with exterior walls.

Slabs are not sealed environments

A grading holder is not airtight. The book inside breathes with the room. MicroChamber paper inserted by the grader slows decay but does not replace a good environment.

See How to store and preserve comics for the rest.

Written by the Rare Comics Collectors grading team. Spotted an error or have a question this guide does not answer? Tell us.

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