CollectionPlnr

How to Store Comic Books to Keep Them Mint

By Alexis Pratsides, FounderUpdated

Why Storage Matters as Much as the Comic Itself

A comic book bought raw in Near Mint condition can drop an entire grading tier within a few years if stored badly. Humidity causes foxing and yellowing. Acid migration from paper pulp eats into white pages. UV light bleaches covers. PVC bags off-gas chemicals that stick to ink. None of this is recoverable - once a comic yellows or develops tide marks, no amount of pressing fixes it. Correct storage prevents all of these problems and keeps your collection at the grade it was when you bought it.

If you track your collection on CollectionPlnr, a properly stored collection is also a more accurately valued one. A book you logged as NM stays NM, rather than quietly sliding toward VG over a decade.

Bagging: Polyethylene, Polypropylene and Mylar

The first line of defence is the bag. Three materials dominate the market, and they are not interchangeable.

Polyethylene (PE) Bags

Cheap and widely available, polyethylene bags are fine for lower-value books you handle regularly. They are soft to the touch, easy to open, and acid-free. The downside is longevity - they yellow and become brittle within 10-15 years, so you need to replace them periodically. Never use bags labelled simply as "plastic" without checking the material, as PVC bags look identical but off-gas hydrogen chloride which actively destroys comics.

Polypropylene (PP) Bags

The most popular choice for modern collectors. Polypropylene is clearer, crisper, and more durable than polyethylene. It remains stable for around 20 years. Most comic shop bags are polypropylene. At a fraction of the cost of Mylar and with very good archival properties, PP bags are the right choice for the bulk of a collection.

Mylar (Biaxially Oriented Polyester) Bags

Mylar is the gold standard for long-term archival storage. It is chemically inert, UV-resistant, and rated for 100+ years of stable storage. It is also significantly more expensive - roughly 10 times the cost of a polypropylene bag. Mylar bags are recommended for key issues, first appearances, Golden Age and Silver Age books, graded slabs awaiting submission, or anything you would not want to re-bag for decades. Bona fide Mylar (E or D grade polyester) is sold by BCW, E. Gerber, and Bags Unlimited.

Sizing: Current, Silver Age and Golden Age

Comic book dimensions changed over the decades, so bags and boards come in corresponding sizes.

  • Current/Modern size - fits comics published roughly from 1980 to present. Approximately 6.875 x 10.5 inches. This covers the vast majority of modern collections.
  • Silver Age size - slightly taller and wider, for books from the 1950s-1970s. Approximately 7.25 x 10.5 inches. A current-size bag will crumple a Silver Age book.
  • Golden Age size - the largest format, for pre-1950s books. Approximately 7.75 x 10.5 inches. Golden Age boards also need to be cut differently.
  • Magazine size - for oversized format titles like Heavy Metal or Epic Illustrated.

When in doubt, size up. A current-size book rattling around in a Silver Age bag does less damage than a Silver Age book crammed into a current bag.

Boards: Acid-Free and Buffered

Boards go inside the bag behind the comic to keep it rigid and prevent spine creases during storage. The key properties to look for are acid-free and lignin-free construction. Standard white cardboard is mildly acidic and will yellow and damage the comic over time. Archival boards are made from acid-free, lignin-free pulp, and many are buffered with calcium carbonate to neutralise any acids that migrate from the comic's own paper.

Boards degrade over time even when archival quality - replace them every 3-5 years for valuable books. When you buy boards in bulk, sniff them before use. A sharp chemical smell can indicate a poor-quality batch.

Boxes: Short vs Long

Once bagged and boarded, comics are stored in boxes. Two sizes are standard.

Short Boxes

Short boxes hold around 150-200 comics and weigh approximately 15 kg when full. They are manageable for one person to lift and move. Short boxes are the practical choice for most collectors, especially those who regularly access their collection.

Long Boxes

Long boxes hold around 300-350 comics and are heavy (25-30 kg full). They maximise storage density but become difficult to move safely. They are best for archival storage of books you rarely access, in a permanent location. Partially filling a long box is wasteful - use a short box instead.

Regardless of size, boxes should be acid-free cardboard. Store them on shelves off the floor to avoid flood damage. Comic boxes should never sit on concrete floors, which wick moisture. Stack no more than two deep per shelf level to avoid the lower box bowing under weight.

The Right Environment: Temperature, Humidity and Light

Physical protection only goes so far. The environment your comics live in does the rest.

  • Temperature - aim for 60-70 degrees Fahrenheit (15-21 degrees Celsius). Heat accelerates chemical degradation. Attics are bad. Basements are risky. A climate-controlled interior room is ideal.
  • Humidity - keep relative humidity between 35% and 55%. Below 35% paper becomes brittle. Above 55% you get mould, foxing, and adhesive failure on spines. A simple hygrometer in the storage room costs very little and tells you where you stand. A dehumidifier fixes most problems cheaply.
  • Light - UV light fades cover colours and bleaches pages. Store boxes away from direct sunlight and fluorescent lighting. If you display comics in frames, use UV-filtering acrylic, not standard glass.

Storing Comics Upright vs Flat

Comics should be stored upright, like books on a shelf, not lying flat in stacks. Stacking causes spine stress on lower copies as weight builds up. Upright storage distributes weight evenly across the spine, which is the strongest part of the book. Use a divider card at the end of each section to prevent the last few books leaning and developing spine rolls.

Handling Best Practices

Most damage happens during handling, not storage. Wash and dry hands before touching unbagged comics. Never flex the spine back on itself. Open comics to around 45 degrees maximum rather than lying them flat. When removing a comic from a bag, tilt the bag and let it slide out rather than pulling it by the cover. For very high-value books, cotton gloves reduce oil transfer.

Graded Slabs

CGC, CBCS and PGX slabs are already protected by their enclosure. Store slabs upright in a dedicated slab box or on a shelf with soft dividers to prevent cracking. Avoid dropping slabs - the holder itself can crack on corners, which may lower the internal grade on resubmission. Keep slabs out of direct light to prevent UV fading through the case window.

What Happens Without Proper Storage: Real Degradation Timelines

It is worth being concrete about timelines, because comic degradation is slow enough that collectors often do not notice until significant damage has already occurred.

  • PVC bags - visible chemical staining and cover damage can appear within 2-3 years of contact. The off-gassing begins immediately.
  • High humidity (above 65%) - visible foxing (brown rust-like spots) can appear within 1-2 years. Mould growth within months in extreme cases.
  • Direct sunlight - noticeable cover fading within 3-6 months. Significant bleaching within 1 year.
  • Acidic boards - brown staining on white pages within 5-10 years. The acid migrates gradually from board to paper.
  • Stacking without support - spine rolls and corner bends in the lower copies within months as the stack settles.

None of these are recoverable. A foxed page cannot be un-foxed. A sun-bleached cover cannot be un-bleached. The investment in correct storage - bags, boards, a good box and a stable environment - is far less than the value lost from a single grade drop on a key issue.

Creating a Storage Rotation and Inspection Schedule

Even with correct storage in place, a periodic inspection schedule adds another layer of protection. Every 2-3 years, pull a sample of boxes and check the bags, boards and a selection of comics for signs of yellowing, smell or moisture. If any problem is found, it is likely affecting all the boxes in that storage area. Catching a humidity problem early - when a dehumidifier is the fix - is far better than discovering it 10 years later when the collection needs extensive remediation.

Mark board replacement dates on the bags (lightly, in pencil, on the back) so you know when the board inside needs swapping without having to open every bag every time you inspect.

For an overview of how grading affects your book's value, see our guide to how comic book grading works. To understand what your stored collection might be worth, visit the how to value a comic book guide.