Mould or something else?

[_henry_]

We've just had a leak fixed in the roof above the eaves in an attic room in our 1930s semi. The previous owner was quite elderly and we suspect that leak may have been there for a while.

There's an unpleasant sharp smell in the eaves that I assume is due to damp/mould.

Having a look around I found some patches of a white powdery substance as shown in the photo. These aren't in the areas that had become visibly damp as a result of the leak.

I'm worried this could be mould, but looking at it I'm not 100% so sure. It has a slightly crystalline quality so it might be something that's dissolved and precipitated out. Or it might be mould.

Can anyone familiar with these things identify it?

 

[vinn]

Remove a little and splash a few drops of water on it - if its salts then the white looking stuff will disappear but if its mould then its fibrous and wont disappear but merely remain.

Thoroughly examine the whole area - do you see any tiny plant like threads?
Is it a mushroom like smell?

 

[_henry_]

Tip with water makes good sense and is obvious now you've said it - thanks.

It dissolved very easily - so looks like it's salts.

That still leaves the smell to track down. It's not a mushroom like smell. It's hard to describe. Quite a sharp smell that I associate with damp. Once you go into the eaves you stop noticing it after a minute or so, but you notice it straight away if you walk into the room and the door into the eaves has been left open.