[nathankaye]

Cleaned sone indian stone slabs today. But plenty were covered in black lychen (lol rubish at spelling)/ black spots.
Client had some chemicals for it, mix ratio was 1 part to 2 parts water. Brush n leave for 10 then rinse. Did so but used fsc to rinse but no real results. Tried it neat and no results. Being careful i used the lance with a 25 degree nozel. Some slabs came up great, others no results at all.  For future reference what is the best to get rid off??      Im thinking hypo but she had a good size pond and where water run offs theres plenty of plant life (meditteranean garden) so not sure??

[serj shergill]

Apply the hypo with a brush ??

[Charlie Allen]

i have one to do a bit like this and had thought about brushing it on. But what happens if it rains? is there a residue  that will be lifted by the rain and revived, washed into the pond? Be a bloody expensive mistake if it does.

[Mike Halliday]

Hypo would eat that for breakfast.....  4-1 put down  by watering can.

If you are worried about run off then put it in a bucket and use a brush. This is an image showing black spots on York stone worse that yours and the result you Can achieve

It dies once exposed to the air, it won't have a residual effect

[Smudger]

Hypo - no need to brush - get a good sprayer "ik" for example and apply





I find it also helps to give it a really strong pressure wash first, this helps break down the black spot

Darran

[Charlie Allen]

Thanks, i usually apply it with an ik sprayer, its just i dont want the run off to kill a dozen or so huge coys

[nathankaye]

Cheers guys ill remember that for next time and best stock up on the stuff.  It seems to be a one stop cure for a number of things ☺
My client was saying a whike ago, her x husband's friend p/washed the slabs once for her. Came in and said job done, i just sprayed some chemicals down and blasted off!  Only problem is most of it end up in pond and she said the fish were jumping out water and bleeding all over place. She'd never seen her hubby cru till that day, she said it was like an horror movie. I asked if they were still friends after that. I cant repeat the answer  but i took it that they werent

[Smudger]

Thanks, i usually apply it with an ik sprayer, its just i dont want the run off to kill a dozen or so huge coys

S the pond raised or got a wall ?? If so you will be fine, if not then leave a minimum distance of 1/2 meter, always apply after pressure washing ( as before it's not only less effective but going to go everywhere.

With customers that have ponds and no retaining wall I advise them that I can not remove black spot that close to the pond

Darran

[Charlie Allen]

Hi Darren thanks for your advice
I always apply the hypo after and never really had a problem. this patio is layered and the last layer goes around the pond with nothing to stop anything running into it. I had thought along the lines of brushing it on but was worried about residuals being washed in if it rained. Mike seems to think once dried there isnt any but still worries me.  I think im just going to tell them they have to live with the black spots

[Smudger]

As koi esp. Large ones are very expensive not to mention people's attachment to them I would also leave the black spot,.

While hypo does become inert over time, I know personally that when re wetting a hypo'ed area it becomes active ( to what strength I don't know ) and foams the water and you can smell it again

You've looked at the risk, and made a decision, that's all good for you and the customer

Darran

[Smurf]

I avoid using chemicals altogether on any type of surface cleaning if they have a pond nearby as is not worth the hassle.

[BDCS]

Koi can be expensive

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