Mold or ~efflorescence?

[soparklion11]

My girlfriend just bought a house, 1950s construction in Pittsburgh, Pa. The slate roof had a leak that has been adressed by a specialist.

What is on the ceiling, under the old leak? The home inspector told her that it was mold and that it could be toxic. I think that it could just be efflorescence through old plaster. Any ideas?

 

[nealtw]

Have it tested.

 

[Skeezix]

That doesn't look like efflorescence to me. Every 3 or 4 years I get efflorescence on the mortar that's between the bricks on the outside of my house. Just on the mortar, not on the bricks themselves. Usually in the protected areas that are under the deck covering. It looks like somebody spilled some white paint on it, but it comes off with a bit of scrubbing using a small wire brush (about twice as large as a toothbrush). (BWDIK)

 

[Jeff Handy]

If the area is not mushy and not too large, I would just scrape and wire brush it off.
Wear a mask and and put down cheap tarps you can throw away.
Work neatly, try to vacuum dust right as you scrape it from up there.
You can stick a big funnel into a shop vac to collect as you scrape, even just a cardboard homemade funnel taped together.

Open a window and have a fan in it pulling air outside.

Bleach it, then let dry for a few days.
Them paint with mold killing primer.
Then do any surface repairs with joint compound, then more mold killing primer, then paint.

Mold danger is highly over-rated, unless you or she are unusually sensitive to it.

I have asthma and allergies, and have literally crawled and wallowed in fuzzy or black mold when working under a crawlspace, under old porches, repairing soggy sheds, etc.
Never had any issues besides some wheezing for a while.

 

[soparklion11]

That doesn't look like efflorescence to me. Every 3 or 4 years I get efflorescence on the mortar that's between the bricks on the outside of my house. Just on the mortar, not on the bricks themselves. Usually in the protected areas that are under the deck covering. It looks like somebody spilled some white paint on it, but it comes off with a bit of scrubbing using a small wire brush (about twice as large as a toothbrush). (BWDIK)

I agree and I've also only seen efflorescence on concrete blocks, I was just trying to figure out if it had a slightly different appearance on on plaster. I completely agree that it having been painted over doesn't help...