Franz Heymann wrote:
:: "Phil L" wrote in message
:: .uk...
::: Mike wrote:
::::: Can anyone suggest a cheap method to clean up my paving ,ive
::::: heard a week mix of Bleach and water bring back the the " as
::::: new look " The paving is only 3 years old ,hopefully I can
::::: catch it early . I dont mind scrubbing ,but domestic power
::::: washers are a waste of time. Thanks Mike .
:::
::: You don't need any specailist stuff and if you do it correctly,
::: you don't need to scrub neither!
::: Buy a tub of caustic soda and mix it according to the label,
::: water it evenly over the paving, preferably when it's damp, to
::: allow it to work before evaporating/drying up.
::: Leave it for 45 minutes.
::: Go over it again with a few watering cans of clean water and give
::: it a good brushing with a stiff yard brush, this will partially
::: rinse it and remove all the dead algy (which incidentally stinks
::: to high heavens when it's killed)....any alkali will kill algy
::
:: I have seen algae grow on limestone

Me too, and on concrete which are both alkaline based, nevertheless, wet
sand/cement seems to remove it, provided of course that it is brushed and
washed away.
::
::: and it doesn't need to be particularly
::: strong - I found this out by accident when using sand/cement
::: which is a fairly weak alkali, brushing up and washing down at
::: the end of the day resulted in clean patches on the green paving
::: stones where the mix had been.
:::
::: When you've give it all a good brushing over, rinse it down
::: thoroughly with the hosepipe, you may need someone to help you
::: here, to brush the water into the drain.
:::
::: *** CAUTION***
::: Caustic soda will take your skin right off and is an irritant
::: even in it's weakest solution.
::: It will bring cold water to the boil when mixed and may give off
::: a sharp smell.
::: If you have any pets or kids they will need to be kept away, and
::: preferably locked up:-p
::: you will need old clothing when using it as it acts like acid.
::: I don't know the toxicity of it WRT plant life but can't imagine
::: that it will do them any good.
::: Only use this method if you are confident that little or none
::: will end up on the soil - it's ok for patio's with drains to wash
::: it into.
::
:: If, as you say, algae hate alkaline conditions, it should not be
:: necessary to go to such drastic measures as using caustic soda.
:: Scrubbing with a washing soda solution, or putting down a thick
:: dusting of garden lime and leaving it in situ for the rain to
:: disperse in due course ought to do the trick.
::
:: Franz

Probably would if my suspicions are correct....it would be worth trying a
few patches of various strength solutions of washing soda and / or bleach
and if they don't work, then weak caustic soda mixture, it all depends on
what size area needs cleaning, if it's only a few square metres then a
weaker solution and more hard graft would suffice, if it's a large area I'd
be tempted to use something quite strong and do less scrubbing.