How do I clean algae stains from old clay pamments/floor bricks?

[confusedyouwill]

Can anyone tell me if it's possible to clean black algae stains from the face of old clay pamments/floor bricks. I've tried pressure washing and scrubbing with bleach with no luck. Anything else I can use? They were laid in my garden, but I want to re-lay them indoors.

 

[thompsonbrown]

you could always try a mix of bleach and bicarb or try steam cleaning. there are also liquid brick and morar cleaners aroundabout £12 for 5 ltrs

 

[confusedyouwill]

I'll try the bleach/bicarb and steam cleaning, thanks. When you say brick and mortar cleaners, do you mean the acid based ones? I have some, based on hydrochloric acid. Was a bit worried about using that after bleach though, even though they have been thoroughly rinsed.

 

[confusedyouwill]

OK, I've decided this is next to impossible. I've tried: bleach, bleach and bicarb, brick acid, white vinegar, white vinegar and bicarb, vanish. Then scrubbed with a metal scourer. The stains have faded but not completely gone. Such a shame as these pamments would be lovely if I could clean them properly. The only other thing I can think of doing is taking the surface off with an angle grinder. Who knew that algae could leave tar like stains?

 

[confusedyouwill]

Quick update. The best method I found was to soak in brick acid then scour with a metal scouring pad. Didn't get rid of the stains completely, but gave the best result out of all the things I tried. If anyone knows a better way, please let me know.