Mold In House!!

[mummybee]

While hoovering up my spare room yesterday there was some mold on my sons guitar case!!!

How did it get there???

The room has some dampness in the walls because its an old building but I keep it ventilated. what's going on here?

[KARL]

What you are seeing is the degeneration of a film of material on the item in question. Most of this material will be house dust, skin oils and sweat and possibly any polish or such on the case, etc. The prerequisite for the mold proliferating to the extent you see is moisture. The moisture is, as you clearly suspect, all down to atmospheric humidity. The reason for it building up to the extent that growth takes off in a clearly visible way is first and foremost low ambient temperatures - had the room been constantly heated to raise the temperature then the room and everything in it would have remained dry to the point that nothing would have been able to grow. Contrary to popular belief, ordinary ventilation ( for example an open window) will not ensure dry conditions in the UK (maybe in the Sahara, but not in the UK) and this form of ventilation may well make matters worse under certain circumstances. Compare when a glass jar or bottle is removed from the fridge - an open window will not stop the condensation forming on it. Similarly, when warm air enters the room, either when a door to it is open or through the open window when there is a sharp rise in outdoor temperature, then moisture will begin to condense on all surfaces in the colder room, maybe not dripping off but there nevertheless.

[The Builder]

This comes up a lot on Answerbank. I think, in future, I'll just refer them to Karl's post.

Sadly, this is the UK. Diabolical climate. Ventilation - yes, but heating to raise the building's temperature above the point at which condensation develops.

Spare rooms need love too ;o)