Best treatment for black marks on patio - Patio Magic?!

[Gettingonabitnow]

Hi

Ive water blasted the patio to within an inch of its life but there are stubborn black spots. Has anyone used a leave on / wash off solution that actually works please?

thanks

Following. It’s white marks on my patio, lots of them! I’ve been trying to decide about Patio Magic.

I’ve used This and This

Both are good, but ones much cheaper. I use it with pump sprayer neat and leave it overnight then jet wash off.

my patio is Indian stone, it may not work as well on artificial stone or concrete.

also don’t wear anything you love, it’s pure ammonia and ruins whatever you wear.

you can actually get the same effect with neat bleach but it’s very time consuming to cover the patio, scrub it and leave it, and the smell is horrendous.

Sodium hypochlorite.

It's like a very strong bleach, doesn't need brushing in. But it will kill any grass etc it touches and pets need to be kept off until it's rinsed off.

These strong chemicals get washed into the ground and leach into the water presumably. They are not environmentally friendly in any shape of form and must be dangerous to wildlife surely?

Bleach degrades into salt and water.

Patio magic is good for anything organic- that green “bloom”, mildew etc. Not so good for other stains like oil marks from food or marks from furniture. So depends what the spots are.

Also you need to use it when it’s not going to rain for at least a day, ideally 2.

@Gettingonabitnow black spots are usually lichen so patio magic, although great, won't shift them.

My patio is Indian sandstone, I used sodium hypochlorite off Amazon. It is basically bleach but at a 15% concentration rather than household bleach which is 3 or 4%.

I did one paver first to test how long I would need to leave it for at a rough 50/50 dilution. Once happy I did the rest, depends on the size of your patio as to how easy this will be. I used a pump sprayer and you need to keep it wet, you can't let it dry out. So an overcast day is best My patio is about 29msq, I only needed one container. We did use a brush to help scrub it in.

Hose down any grass or wood etc that is next to the patio, wear old clothes and a mask when you mix it. Follow all the manufacturer's instructions.

@BenchOfCompany could I check, when you say keep the solution damp, why is that?

@SallyLockheart I don't know why but I was nervous about putting sodium hypochlorite on my sandstone patio and watched a lot of videos by professional power wash people cleaning patios. They said don't let it dry out so I didn't.

I think the reasoning might be that on a warm day it could evaporate and so won't work as it needs to soak in, on a wet day you don't want to dilute it any more than you have.

I am a firm believer in testing a small area first, hence why I did one paver first.

oh, that does make sense. will also youtube it - there aren't many practical DIY things that can't be helped by youtube!

will give it a go. thanks

Sodium hypochlorite (often also known as red label).

It is used to clean dairy equipment and is usually £10-15 for 25l at your local agricultural merchant, or three times that at our local ‘equine’ agricultural merchant.

@SallyLockheart You're not wrong. YouTube has helped us install bathrooms, tile the kitchen, fit flooring, install fencing, see reviews on tools etc. It is an incredible resource. We could get someone in but there is a serious sense of achievement when you do it yourself.

Ds1 learned to play both piano and guitar from YouTube tutorials. Plus I love watching people build houses or renovate beautiful period properties or even a French Chateaux .

@Asdf12345 good to know that.

Hah. Your ambitions are a higher level than mine - minor repairs only

Apart from dirt, black patches on patios is usually mildew or some kind of mould.

Encouraged if the surface is persistently damp, because it has been laid without a good fall and/or gets no sunlight to dry it out. There may also be green moss if wet.

A chemical called "wet and forget" kills it and prevents regrowth for a few months, but I think the only good cure is to resurface it with a good slope so rain runs off and does not linger in puddles. The surface must be 2 brick courses below the DPC so may need to be dug out, not layered over.

Sometimes there is a leak, or rainwater downpipes, or dripping overflows, or broken gulley or drain, that contributes to the persistent damp and needs to be repaired

I do not recommend jet washers because they abrade the surface of the concrete and you will find you get loose grit and exposed aggregate (gravel).

I have seen bleach take the colour out of coloured paving slabs.