Indian sandstone patio sealant recommendations?

[vk2003]

I have a large 9yr old Indian sandstone patio which goes green and needs power washing every year. The only thing that seems to delay this discolouration is sealing it which was done a few years ago by a gardener. That layer appears to have worn off and is like to seal it again after cleaning it this year. 

Can anyone recommend a good sealant please? There seem to be a plethora of them available so I’d like to use something as long lasting and effective as possible!

 

Of course, if sealants are a load of baloney, I’m equally open to advice. 

[FarmerN]

We laid our Indian sandstone last spring, supplied by Westminster Stone.

They were indifferent about sealing, but as I wanted to seal supplied “Mattstone H2O Seal 2”

We only did part last summer , it still went a bit green over winter but not as bad a unsealed part.

The downside to sealing was it was like a waxed car, great droplets of water collecting on the surface,  the unsealed part dried out much , much faster after rain. Both areas needed a good clean this spring.

Wesminster Stone recommended not using a power hose to clean it with saying this would make the surface more open by washing bits out. Suggested that we should wash when needed with proper cleaner, ( which of course they sell !) I used dilute acid , a brick cleaner, first and after rinsing, washed again with a soap bleach mix . I’m sure domestos or similar would be fine, but I used agricultural Sodium Hypochlorite mixed with fairy liquid, mixed at about 750ml Hypo +250 ml fairy to a bucket of water. Use with care splashes will sting and bleach clothes. Brush over, leave to soak and wash off with hose. Worked well for me all green washed off. Think the bleach is the important bit.

 Do Not mix the bleach with the acid !