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Preservation Interest Group

Guide to provide a forum to learn and share ideas about the various aspects of preservation.

Meeting Notes

The February 4, 2020 Preservation Interest Group meeting on mold was attended by 11 people representing 9 institutions. 

Facilitators Ann Kearney and Karen Kiorpes led a very energetic discussion on how to identify mold, deal with it, and prevent it from returning. 

The next Preservation Interest Group meeting is scheduled for Tuesday, April 7, 9:30 - 11:00 am. 

Meeting Notes

Several meeting participants discussed mold they had discovered in their institutions. Karen and Ann noted that you can freeze moldy material while you are considering options.  If possible, freeze dry wet material. Freeze drying freezes items under pressure so the water does not turn back to a liquid state during the process. It pulls moisture from directly from frozen books and papers. This avoids the wet state when material is more likely to tear and when print and colors on items can easily bleed.  

If items are slightly damp, can dry manually by fanning pages and spreading out in dry space. Can also wrap in butcher paper and keep in freezer until you can deal with the items. 

Can put material in heavy poly bags (see resources below), but this is a temporary solution to isolate them from other, unaffected materials. Items should not be kept in the bags long term, and must be dealt with fairly quickly. If items are soaking wet, put in freezer until you figure out what to do. This will inhibit mold growth. 

If moldy items are replaceable, it is safer and more cost efficient to replace and throw out moldy items rather than remove the mold. 

Foxing is not mold. You do not need to worry about foxing spreading to other items. It is caused by metals in the paper. If you are not sure if something is mold or foxing, dirt, stains, or something else, you can use an ultraviolet light, Mold fluoresces with a green-yellow glow under ultraviolet light. Karen demonstrated this for the group. University at Albany has an ultraviolet light, and group participants are welcome to use it. (Ultraviolet light can also be used to help read faded inks.) You can also use a magnifying class to help identify mold. Mold is more furry than other things that may be causing staining. 

If mold is just on the covers of bound items, you can remove the covers and have them rebound, as long a the inside pages are not wet. As mold grows, it eats the cellulose in the pages of the book, so if mold growth is too far along, the book may not be able to be rescued. If mold is dry and dormant, you can put the item in a poly bag and shelve with the rest of the collection. 

Hepa vacuums can be used to remove dried mold. Cover the end of the vacuum in cheesecloth and set at lowest setting. Do not put vacuum brush directly on item. The video in resource section below demonstrates this method. 

As with allergies, some people are more sensitive to mold than others, and sensitivity can develop over time. If you are highly sensitive, ask someone else to deal with moldy items. You may also want to use N95 masks, goggles and nitrite gloves when handling moldy items. The masks filter out most particles, but need to fit tightly, so may not be effective on people with facial hair. 


Routinely check for leaks, especially in areas that are not often visited. You can buy local water alarms at hardware stores for a reasonable price. A very loud alarm will go of if the area gets wet, so put in areas prone to leaks. 

Try to keep humidity below 60%, especially in hot weather. Fans and dehumidifiers can help, but make sure the dehumidifier is the proper size for the space. 

Keep items away from exterior walls, especially if you do not have good humidity control. If you must have shelves against exterior walls, make sure that items do not touch the walls.

Do not use fire proof safes and cabinets for storage. They have an internal layer that releases moisture when it gets hot. They can release moisture when there is hot weather, which can lead to mold. A regular safe or archival boxes are a better choice for historical materials. 

Can use items like mildew control bags, popular with people who store boats, to reduce mildew. Schuylerville Public Library staff noted that they hang a product called Damp Rid in their small storage space to reduce mildew. It works well and lasts about 3 months. 

Dealing with Odor

Items may retain an odor of mold, mildew, smoke and other scents even after treatment. If items have an especially strong odor, reformat them and throw the originals away when possible. Materials can be sent out for ozone treatment, but this will discolor the paper. 

You can use microchamber paper to trap odor molecules. Interleave this paper every few pages and enclose the items in a poly bag. Remove them after 2-3 weeks and throw the paper away.  

You may also use the tub within a tub method. Put material is a smaller tub without a cover. Put unscented 99.9% dust free cat litter in the bottom of a larger tub, put the smaller tub with item in larger tub and cover for several days to weeks, checking occasionally. You must deal with mold before doing this. Method works well to remove mildew smell once mold is gone or dormant. 

Retail items meant to deal with smoke odor, such as Gonzo brand, also work well for mildew.

Next Meeting

The next meeting is scheduled for April 7 at 9:30 am at CDLC. The tentative topic is library security. 




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