I wish I had fore thought and had taken a couple of pics. I was waiting ten minutes today in the drizzle for a client to come and give me access to a property and the outside wall of the extension was algae green (on white paint) well you know how a bored cleaner likes to fidget and experiment. I grabbed a bottle of Domestos spray bleach I had out the van and sprayed up a two square feet, agitated with brush lightly, left for 5 mins then rinsed with the WFP no extra brushing and it all just melted off. Customer pulled up and caught me. 'How much for the whole wall'?, 30 m2 is about all. 'Oh I reckon about £120 will cover it'... 'Get it done' says he. Easiest £120 I made all week! No wonder it's called soft washing!