Hi Ron,
thanks very much for your input. I will get some dessicant packs.
The room is a tiny bunk room, so the dehumidifier is very efficient in that space. However, it used to be a mouldy room, so there must be spores in there.
My bedroom wardrobe, which is not as dry as the bunk room, but has not had such severe mould problems. I checked some boxes of prints in there today and they seem ok, which is a relief.
So it would seem that humidity levels aren't the only factor. If there has been mould in the room before, then it seems from this experience, that the room will always be prone to that problem - maybe unless it is cleaned out thoroughly with bleach.
best wishes,
Richard
On 16 September 2014 10:23, Ron Williams ronwatl@... [DigitalBlackandWhiteThePrint] <DigitalBlackandWhiteThePrint@yahoogroups.com> wrote:
Most dehumidifiers won't drive moisture levels much below 30% RH. Mould will definitely grow at that level. I never store photos in wood or cardboard containers or in paper folders (provides mould growth medium) - metal only. I use glassine sheets to separate the photos when stacked. If you really want or need to drive the moisture down, use desiccant packs in the closed storage container (in addition to a general humidity control). The photo media/paper itself could be attractive to mould. Mould is insidious - I used to live in Florida and had growth in bright sunlight and sometimes surviving occasional (diluted) bleach baths.
Sent from my iPhone...
Ron Williams