Humidity levels in a library?

[Pitlamp]

Not sure if this is the best place to post this question - but here goes.

Can anyone advise on the optimum humidity range for a caving club library?

We have humidity meters monitoring ours - and monitoring the effect of running a dehumidifier (which is considerable). But there's no point having the dehumidifier on any more than necessary to ensure the material isn't going to degrade.

I'd be grateful if anyone can point me in the right direction; thanks.

 

[huwg]

Not sure if this is the best place to post this question - but here goes.

Can anyone advise on the optimum humidity range for a caving club library?

We have humidity meters monitoring ours - and monitoring the effect of running a dehumidifier (which is considerable). But there's no point having the dehumidifier on any more than necessary to ensure the material isn't going to degrade.

I'd be grateful if anyone can point me in the right direction; thanks.

Caring for rare books

www.nls.uk

Says as constant as possible 45-60%

British library may also have some info (I'm sure they have a book on it too!).

 

[Steve Clark]

You may already be aware, but if you are considering the cost of running the dehumidifier, compressor-based units are better for habitable temperatures (18-20degC). If the average temperature is generally lower (~10degC) the heat pump efficiency drops right off and you are better with a desiccant-based unit but with some proper control so it cuts off when it reaches your target humidity.

Edit : (That being your relative humidity at a particular temperature. When the unit cuts off, it stops providing waste heat and the air cools down due to thermal losses to outside. You will then see an increase in relative humidity without adding any airborne moisture from anywhere. The unit will then kick back in. It would be useful to know what the book boffins think about both Humidity & Temperature to ensure you're not causing a damaging cyclic effect by having the dehumidifier).

 

[Pitlamp]

Thanks - I believe it's possible to buy humidistats for that purpose?

Both your post (Steve) and huwg's above have told me very useful things.

I'm hoping that other clubs may benefit from any consensus within this topic as well.

 

[ChrisB]

The National Archive is in a salt mine in Cheshire, naturally 60% and brought down to 50% as optimum.

See http://www.essexrecordofficeblog.co.uk/visit-to-deepstore/

 

[Jenny P]

Worth enquiring of your local Record Office as this may depend on where in the country you have the paper records you need to store. Transporting items from the S.E. of England or Scotland to Cheshire, for example, would be expensive.

There would presumably be different conditions required if you were storing photographic material: prints, negatives, slides or even glass plates.

 

[Bob Mehew]

Try this link from the Smithsonian, a reliable source. But you are likely to have more trouble with modern publications being published on crap paper using ink jet inks. As are biros in manual records. So if you want security, then scan the material and keep the records in a separate location. Also bear in mind that photographic records (both slides and prints) need care.

 

[Pitlamp]

Thanks folks - yes, scanning is on the agenda eventually.

 

[Bob Mehew]

scanning is greatly helped by having a program which will undertake optical character reading and produce a hidden data set which you can copy and paste the words to somewhere else.

 

[caving_fox]

And to save yourself having to do it again very carefully consider the digital medium you're going to store the results in. Many 'permenant' archives from the 90s are lost because no-one can read the 5.25 floppy disk anymore. You also want to consider searchability - images generally aren't.

Museums have conservation departments who can advise on mixed media storage. Local universities also often helpful.

 

[Pitlamp]

Thanks for the two posts above; I follow your reasoning and will be consulting club members who are far more IT literate than me about creating an appropriate database of contents. I also hope to pick the brains of those who run (and have indexed) the British Caving Library at some stage, before starting. No point re-inventing the wheel.