Comic books are printed on paper — an inherently unstable material that yellows, acidifies, and becomes brittle over decades if the storage environment is wrong. Most comic damage happens not during reading but in long-term storage: from contact with PVC bags, from acidic cardboard boxes, from staples that rust and stain the surrounding paper, and from humidity that accelerates every chemical degradation process. The good news is that the correct materials are inexpensive and the correct conditions are easy to maintain. This guide covers everything needed to store comics properly at home.
Bags: the first line of protection
The standard comic bag is a polypropylene or polyethylene sleeve. Not all plastic is equal. PVC (polyvinyl chloride) bags release plasticiser over time that yellows paper and can irreversibly damage covers. Any bag that feels slightly sticky or has a strong plastic smell should be discarded immediately.
The correct choice for long-term storage is a Mylar bag (made from biaxially oriented polyethylene terephthalate, the same material used for archival document storage) or a certified archival polypropylene bag explicitly labelled "acid-free" and "PVC-free". Mylar bags are more expensive (approximately 0.30 to 0.60 euros each) but are chemically inert and last indefinitely. Current issues can use polypropylene bags, which are less expensive and adequate for medium-term storage of non-valuable copies.
Backing boards: keep the comic flat
Every bagged comic should also contain a rigid backing board to prevent bending and provide structural support. Backing boards must be acid-free. Standard white boards made from acid-free cardboard are available in current size (for comics from the 1970s onward) and silver/golden age sizes (for older, slightly larger comics). Replace backing boards every 3 to 5 years as they absorb acid from the comic paper over time.
Staple condition: the hidden threat
The staples that bind comic books are steel and will rust if exposed to humidity. Rust stains spread outward from the staple holes into the surrounding paper and are impossible to reverse. For any comic with collector value, inspect the staples under good light: the first signs of oxidation appear as orange or brown discolouration at the staple itself. Once rust is visible on the staple, the damage to the paper has usually already begun.
Do not attempt to replace staples yourself unless you have the correct period-appropriate stapling equipment. Restoring staples without specialist tools reduces the CGC grade immediately. For high-value copies, CGC offers a "restored" designation that documents any staple or paper work, which is not the same as an unrestored grade.
Boxes and shelving
Comics are stored vertically in dedicated boxes, not horizontally stacked. Horizontal stacking under weight compresses and warps the comics at the bottom of the pile over months. The two standard box sizes are the short box (holds approximately 150 to 200 comics) and the long box (holds approximately 300 comics). Boxes must be acid-free corrugated cardboard; standard moving boxes are not appropriate because ordinary cardboard is highly acidic.
Store boxes in an interior room away from exterior walls, which are subject to temperature fluctuation. Never store comics in a garage, attic, or basement: temperature swings and humidity in these spaces cause more damage than almost any other factor.
Temperature and humidity targets
The ideal storage environment for comics is 18 to 22 degrees Celsius and 40 to 50% relative humidity. Above 60% humidity, mould becomes a risk within weeks. Below 30%, paper becomes brittle and prone to cracking at spine folds. A standard air-conditioned interior room in most climates meets these conditions without additional equipment. A small hygrometer (available for under 10 euros) placed inside the storage room confirms the conditions are within range.