Black spot removal - Neewbie

[Qwerty24]

Hi all,

Quick thanks to all the advice and guidance I’ve read on this forum over the past few months.

I have a slight issue.
Im very new to jet washing and only trying it as a side project to my other business.

Currently on my 1st job where the slab has required Hypo for black spots, however I don’t feel it’s working like I’ve seen on many videos and threads.

I opted for the 10% Hypo from a local pool shop.
I have tried a 1:4 mix and a 1:3 and scrubbed but still very little change. I tested a spot with just neat Hypo and that doesn’t seem to have done anything all this after 20-30mins for it to work.
I’m applying with a small 5l hand pump spray and some washing up liquid.

I will upload the photos of the before and after stage of my current progress. Any advice would be greatly received.
AJ

Edit: images are currently too large to upload atm

 

[K in Kent]

Personally I always use 15% hypo but I'd srill expect 10% to work at that dilution and definitely neat. A pump up sprayer is fine to use (make sure you wash it through with clean water every time or it won;t last long).
Perhaps it's an old batch of hypo that's lost its potency?
Would seem there must be something wrong with it if it's not working. I'd take it back and complain.
Maybe someone else has got a better idea what the issur could be??

 

[Dave B]

Sounds like hypo is old
Once treated try a quick blast with pressure washer as once it’s hypo’d it should lift easily
Are you scrubbing it in after applying?

 

[THL4KEL]

Just use it neat if it's not coming off. I use 10 percent all the time.

 

[Qwerty24]

Thanks for the reply’s.
I have come back today after buying 14/15% hypo. I tried a test patch at 1:2 and left for 30mins, and while it’s faded the spots slightly it hasn’t gotten rid of them.
I have just done the full patio with basically neat hypo plus Fairy (I know I know, but I don’t have an alternative that would have arrived in time) and left for about 30mins. Again, it’s lightened everything but still not going as I’d expect.
About to do another run with neat hypo and leave again. I haven’t jet washed anything off yet as I’d assumed rinsing it off would have done some good?
Are there slabs/tiles that just won’t release the algae etc?
Is steam cleaning a guaranteed solution?

Thanks in advance

 

[matt1458]

Thanks for the reply’s.
I have come back today after buying 14/15% hypo. I tried a test patch at 1:2 and left for 30mins, and while it’s faded the spots slightly it hasn’t gotten rid of them.
I have just done the full patio with basically neat hypo plus Fairy (I know I know, but I don’t have an alternative that would have arrived in time) and left for about 30mins. Again, it’s lightened everything but still not going as I’d expect.
About to do another run with neat hypo and leave again. I haven’t jet washed anything off yet as I’d assumed rinsing it off would have done some good?
Are there slabs/tiles that just won’t release the algae etc?
Is steam cleaning a guaranteed solution?

Thanks in advance

For black spot that neither hypo or pressure washing touch, this is my go to product: https://floorseal.co.uk/product/black-spot-remover-plus/ it’s the only thing I’ve ever used that’s worked on a couple of jobs we’ve done.

Isn’t cheap though as you basically end up using it neat but if you’re only spot treating certain areas a 5l tub will go a fair way. Worked for me on multiple jobs.

No idea what’s in it vs hypo. I assume it’s napalm

 

[ched999uk]

Some surfaces the algae embeds it's self in and below the surface. I have seen some have some good results with biocide on the 'black spot' that hypo hasn't removed but it takes a good while to work - it's not virtually instant like hypo normally is.

 

[Dave B]

Mapgas blowtorch would burn them out

 

[Pjj]

Thanks for the reply’s.
I have come back today after buying 14/15% hypo. I tried a test patch at 1:2 and left for 30mins, and while it’s faded the spots slightly it hasn’t gotten rid of them.
I have just done the full patio with basically neat hypo plus Fairy (I know I know, but I don’t have an alternative that would have arrived in time) and left for about 30mins. Again, it’s lightened everything but still not going as I’d expect.
About to do another run with neat hypo and leave again. I haven’t jet washed anything off yet as I’d assumed rinsing it off would have done some good?
Are there slabs/tiles that just won’t release the algae etc?
Is steam cleaning a guaranteed solution?

Thanks in advance

You can’t just apply hypo and expect black spots to disappear like magic you need to pressure wash as well sometimes it pays to pw first then apply hypo scrub in with a stiff brush to get the mix into the surface of the black lichen the hypo will then start to break it up , leave for 20 muinits then pw and they should go ,all this comes down to experience it takes time to learn how to do theses things . Steam will remove them easily but not many have a doff at 150 degrees having said that 100 degrees will remove all organic growth and paint

 

[WindyinNorfolk]

As above - p/w first and use a turbo nozzle as this cracks the 'shell' of the black spot allowing the hypo to get inside and remove it