patio slab cleaner

[fishing81]

I have given our patio slabs a clean with a pressure washer but it's left some black marks,can anyone recommend a patio cleaner which will help to clear them

[abstibus]

Sodium hypochlorite from a farmers' supplies or similar is the best. Dilute 1:3 with water, sprinkle on, wait about 10 minutes and then hose off. Be careful, as it has a strong bleaching quality - farmers use it to clean milking parlours.

[TonyV]

fishing - what are your slabs made from?

[fishing81]

thanks for the info annemollie will give that a try and TonyV they will be concrete they are not made from sandstone or similar

[TonyV]

if concrete and NaOCL does not work (it is very corrosive and chlorine fumes can cause internal burns) use a standard patio cleaner - most normally have a dilute acid in them - normally HCL (Hydrochloric acid)

[fishing81]

thanks TonyV willhave a look at the patio cleaners

[modeller]

The last time I used a bleach based patio cleaner all the cats in the area came visiting . They love the smell and love rolling on it .

[fishing81]

I shall only try the stuff on one just to see how it goes thanks modeller