Mold & Mildew Summary                                                       Home Up

     by Danny Etloh

See Also:
Understanding Mold
Prevention of Mold
Treatment of Mold
Storage Materials

When the discussion of mildew in the games comes up, I asked for solutions from libraries with (bitter) experiences on the issue.   What follows is a short summary.

Mildew requires these things to grow:

  • Humidity – generally a relative humidity of 70%, though some can grow at 40%

  • Food – the games and books under discussion in this case

  • Temperature – between 32 and 97 degrees F; 79 degrees is optimum

  • Air Circulation – weak air movement

  • Light – dark to dim light

Mildew comes in two stages – active and inactive.  Active mold is growing, moist, and very hard to clean from paper.  Inactive mold is, obviously, the opposite, with one caveat – you’ll never get rid of ALL the mildew.

If your game has been assaulted by mildew, the following steps are recommended.

  • Isolate the item.  Put it in a plastic bag and/or move it away from everything else.  Otherwise, everything will become contaminated.

  • Inactivate the mold.  Best done by freezing or drying; 6 hours or more in a freezer (less than 25 degrees F) or a location with less than 25% relative humidity.  Putting the item in a slow oven to inactivate the mold will degrade the quality of the paper – it becomes “aged” and brittle.  These methods do not kill the mold, they simply inactivate it.

  • Either outdoors or in a VERY well ventilated location, sweep off the dried mold.  A repeatedly recommended solution is to weight down the paper with a screen, then vacuum the paper with a wet-dry vacuum.  The vacuum should circulate through a solution containing a fungicide, which includes bleach Lysol, to kill inactive spores.

  • Supplementally, you may expose the item to ultraviolet for ½ to 1 hour.  More can be harmful to paper with the same results as baking it for a while.

  • Clean the shelves/storage area from which the item came with a good fungicide solution.  Vacuum with the previously mentioned wet-dry vacuum.

  • Set the contaminated item in an isolated location which is dry with good air circulation, and observe it for at least a day, and up to 6 weeks.  If it doesn’t redisplay symptoms, return it to its “spot” and check it daily for about a week.

Know first that the infection is in remission, and could come back if the environment allows.  Know second that everything (walls, furniture, other games) which was near the infected game is also probably infected, and will probably show symptoms if the environment allows.


Not perfect, but this helps.  You can’t remove the food.  You can, however, affect light, humidity, and temperature.

  • Light:  daily exposures to sunlight through a window, or other sources of good light (not the 25 watt night light in the corner) will make it hard for mildew to activate.

  • Humidity:  Unless you live in Arizona, Libya, or somewhere similar, you should try and dehumidify the storage area.  Try to keep the area below 55% RH, or better, 45%.

  • Temperature:  Obviously, a perfect situation would be to keep the games in a freezer.  Most spouses and others who use their freezers for food may object.  Since the comfort range for mildew is about the same as for grognards, you’ll have to live with it.

  • Air Circulation:  Insure that the location is in the air flow.  Mount a fan, remove hanging towels and blankets, etc.

There are professionals who clean mold and mildew for libraries and archives.  Their fees run from expensive to very expensive, to pay for the skill, insurance, equipment, and time.  But of you have the money, they will probably do a much better job.

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