Surface Mould!

Hello All,

Just a quick query in case any of you have had a similar problem. Over the last few months I have been renovating a room in my house and have included lots of shelving space for my books; all of which are hardback and many of them are folios. All this has been great as they finally have a place and the room is finished. However, much to my distress I have noticed over the last few weeks that some of the books have started to develop a kind of light surface mould upon them, mainly on the visible spines. It is not to difficult to clean the books up when this happens, but it is deeply annoying, and I have just found a few more books with it on. It mainly seems to affect buckram bound books, but even them it seems quite particular with some never showing signs of it and other seeming much more susceptible.

The room does not get direct sunlight and does not seem to suffer from mould in in other places, e.g. on the walls etc.

Any ideas on how this situation can be dealt with? All I can think of is leaving the window open a crack to help air circulate. I have no idea how to check the humidity of the room or what an ideal level for it is...

Many thanks for any advice!

You don't say where you are, or if the room is in a basement, on an outside wall etc. I live in Ontario, where there's high heat and humidity in the summer, and dry extreme cold in the winter, so climate control is a must. A/C with an extra dehumidifier in the basement, and central heating with a built-in humidifier. From the sound of it a dehumidifier would help you. They're noisy and a nuisance to empty, but effective. If the room has new plaster or concrete these take a long time to dry thoroughly.
I have some Folios dating from the fifties, and have never had trouble with buckram, other than a slow fade. Silk fades, rapidly, parchment browns; thin leather as used in the Coghill Chaucer will flake. Soft paper sides such as the Madame duBarry will develop the mange. The best thing you can do for your books, other than keep the humidity constant and air flowing, is keep out the sunlight, even indirect. UV rays kill books.

>1 LowlightLamp:
I'm guessing you live in a cool, damp climate without summer climate control. Mold is always caused by moisture, and the only way to deal with it is by air conditioning or a dehumidifier.

I live in Oklahoma where year-round climate control is essential, and none of my 40-50-year-old books show any deterioration.

>1 LowlightLamp:
It's very easy to check for humidity levels - just buy a simple humidity meter. They're cheap, come in both digital and old arrow on a dial format, and super easy to understand - the levels of humidity (e.g. dry, normal, too humid) are either displayed by the digital meters or the ranges are marked on dials. Search amazon for "humidity meter" and order one. They often come in a combo with a thermometer.

Keeping books tightly packed on a shelf will prevent mould on the front and back covers. Another reason to fill up your shelves with more books!
Otherwise I agree with the humidity control suggestions above.

I had the same problem which has affected a small number of books. It does not seem to be related to the materiels used as sometimes only one volume of a set is affected. I found a dehumidifier running on a low setting has solved the problem.

Like other people have said, get yourself a dehumidifer. These are cheap to run and will eliminate your problem. Without an elevated RH, mould cannot grow.

Thanks everyone for the advice! I have bought a humidity meter and have an old dehumidifer and so have started putting that to use.

I live in the N.West of England by the sea so the air ins never dry anyway, plus it is an old house where damp and condensation are always a problem.

Does anyone have a idea of the ideal humidity level for maintenance of a room with lots of books? The initial reading was in the mid-70s and with the dehumidifer on it has taken it down into the high 60s, but I think I read it needs to be 40-50, so I might need to by a new dehumidifer!

Many thanks.

The consensus seems to be around 35% as ideal, with heat at or below 70 deg. In NW England heat might not be a problem ;) Keeping the conditions constant is also important. I'm not sure how much salt air affects books -- it certainly affects outside a/c units by rusting them.
It's a pretty complex subject, especially for an older house not designed for A/C. Over time altering the air inside the building can compromise the structure. However if the place is often damp dehumidification is good for humans as well as books.

>8 LowlightLamp:. I'm also in NW England in an old house, although some distance from the sea. When I bought my dehumidifier about 2 years ago I left it running on its highest setting for about 3 days which brought humidity down to about 40%. Since then it has run on its lowest setting (which switches off at a humidity level of 60%) and this seems to have solved the problem. Running at this level costs about 70p a day.

>9 Jayked: I don't think there is any need to go to 35% (I actually think that is too low). Anything below 50% is absolutely fine for controlling mould (and is good for human health).

The BL, which aims at perfection, gives a range for mixed library and archive collections of 13 to 20 deg. Celsius, and 35 to 60% RH, noting that when RH rises above 65% the threat of mould becomes significant. The lower end of the scale probably isn't attainable for a private residence without modern insulation and central air. So you do the best you can.

The Library of Congress has this advice:

"Good storage significantly prolongs the life and usability of books and includes:

A cool (room temperature or below), relatively dry (about 35% relative humidity), clean, and stable environment (avoid attics, basements, and other locations with high risk of leaks and environmental extremes)

Minimal exposure to all kinds of light; no exposure to direct or intense light

Distance from radiators and vents

Regular dusting and housekeeping

Shelving books of similar size together, so that the face of the covers are maximally supported by the neighbors on each side

Keeping upright shelved books straight and not leaning (storing books lying flat is also good)"

Thanks again everyone for the further advice. I have got a dehumidifier and have tried to improve airflow as well so hopefully this will take care of the situation from now on. I will just have to keep a beady eye on the books over the next few weeks...

So I have just noticed some light mould on a solander case and commentary volume that I recently purchased. The book itself seems fine, and I have separated it from the case but is there are any way to treat the case and commentary to remove it?

Have seen people suggest denatured alcohol or hydrogen peroxide, but any recommendations from the forum? In the UK denatured alcohol is Methylated spirits, which really stinks. Any other alternatives likes Isopropanol?

>15 Juniper_tree:

Guidance seems to run from "you can simply brush it off" to "burn it. Don't let it infect the rest of your library".

If it's just on the surface you may be able to just brush it off. Sunlight is apparently a good disinfectant. Make sure you deal with the mould somewhere well ventilated or ideally outside and mask up as mould is a carcinogen.

If there's a residual stain I would try the mildest cleaning methods first, remembering that any thing chemical or abrasive will be permanently damaging the paper.

But if the mould has got into the paper the way mould gets into bread, it may be impossible to remove.

>1 LowlightLamp:

The suggestions above are well-informed and accurate. Similar to w.carter, I have a high-end fine and private press book collection and proper care is essential. To summarize:

1. Avoid exposure to direct sunlight. Ideally, place books on shelves in the darkest areas of your house. My most valuable books are stored in well-ventilated closets that avoid exposure to sunlight altogether.

2. Use a dehumidifier and a small humidity meter. I keep my book collection at 40% humidity, which is (for me) ideal for both books and humans.

3. Air conditioning, with ideal year-round temperature of about 70 degrees Fahrenheit.

4. For books with spines exceptionally prone to sun-fading, i.e., silk or silk-like cloth, fine morocco leather and books with red-colored spines, etc., I simple turn the books inward with the spine facing the back of the shelves. I do not need to see these book titles and I can easily remember what they are.

For reference, I live in a region with hot, humid summers and very cold winters. Using these simple measures I have never had any problem with mold, mildew, bookworms, foxing, etc. These simple measures do indeed work!