What's this stuff?

cormie

Hi,
This stuff has been on the walls of an outdoor concrete shed for a while, it's there through the summer as it is the winter. It falls off easily even if you just touch off it. It appears to have grown as it wasn't there from the start.

See this picture to see what I'm talking about: http://img258.imageshack.us/img258/3995/dsc00016ac.jpg

Just wondering if anyone can explain what it is, what it's caused from, should I keep scraping the walls clean of it or just leave it be, are there any dangers from it etc?

Just to note the shed can get a bit damp in that if it rains heavy, it drips a bit from the ceiling. It's actually a shed under a stairwell so the roof of it is basically tiled steps.

Any feedback appreciated

enda1

Looks like a salt - potassium nitrite maybe?

Burn it and see how it reacts! If its the above salt it should burn quite well, lots of smoke.

Think its a by-product of mould growth. caused by damp, cellar like conditions.

sydthebeat

it appears to be a significant case of effervescence.

"Efflorescence is caused when soluble salts and other water dispersible materials come to the surface of concrete and mortars."

http://concreteconstruction.net/industry-news.asp?sectionID=710&articleID=233348

its not something to worry about, it will eventually stop forming. Just keep cleaning it off if it is unsightly

cormie

Jaysus, talk about quick replies to an odd question

Is it the two things stated so? Is efflorescence the same as potassium nitrate?

sydthebeat

im not a chemist but i think both potassium nitrate and calcium carbonate are types of salts.... just depends on what type.

the resolution of teh problem should be the same.

cormie

Cool, well as long as it's nothing to worry about Thanks for all the replies!