Removing Stains from Fertilizer on Patio Slabs

Doesn't matter whether it's white vinegar or white wine vinegar, both are mainly acetic acid. The acetic acid. So you form ferrous acetate which is water soluble.

 

I used a tub of Oxalic Acid once. It worked. You'd buy it from a woodworking supplier.

 

Rings bells, we used to use it to remove black staining on oak caused by contact with ironmongery etc. If I remember correctly.

 

Yes oxalic acid will work, make sure you wear gloves and eye protection when using it as it less human friendly than either vinegar or citric acid.

 

Thank you both. Found it hard enough to find places in Ireland that have it in stock.
Can get these oxalic acid crystals, so will order these. Presumably have to dilute them in water and will apply to one of the slabs and see what happens.

Buy Oxalic Acid online in Ireland at Lenehans - Hardware For Generations