How do I remove wet harling stains from concrete window sill

Discussion in 'Plastering and Rendering' started by self builder 123, 19 Sep 2009.

  1. self builder 123

    self builder 123

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    Hi

    Can any one advise on how best to remove wet harling stains from pre cast concrete window sills ?

    The top coat of the wet harling used while ordinary portland cement.

    I thought about using brick acid, but am worried that it will attack the cement in the pre cast concrete sill and damage them.

    If I were to try a wire brush would the metal dust left behind then start to rust ?

    Any help would be much appreciated.
     
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  3. roughcaster

    roughcaster

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    I know it's a bit late now S/B123, but one of the the first things a roughcaster/builder would do, is to cover the sills with a layer of fine sand, just to protect them from the cement droppings I don't know how you would remove the stain, i "don't" think i would use a wire brush though,,,, maybe a rub with a carborundum stone across the whole sill ??? try a small inconspicuous area (an upstairs/or out of the way sill),,, it might work,, who knows. Maybe some of the other guys on here might have a solution. DON'T use "anything abrasive" though if the sills are finished with a sandy texture, (you'll ruin them),,, the smooth finished pre-cast ones would not be a problem.

    Roughcaster.
     
  4. self builder 123

    self builder 123

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    Hi Roughcaster

    Cheers for your reply.

    I have uploaded a picture of one of the pre cast concrete sills. Please ignore the roughcast - it is currently lying in a heap awaiting disposal !

    All the sills have this white cement staining on them on the front face and also underneath.


    The sills are all smooth finished.

    As a last resort we plan to use brick acid, but are concerned what it might do to the surface of the sills.

    Have you ever had to use acid ?
     
  5. self builder 123

    self builder 123

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    Hi Roughcaster

    I have added a zoomed in photo of the sill which shows the white staining.

     
  6. roughcaster

    roughcaster

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    I see the staining you refer to. It doesn't look that bad really, and maybe over time it will fade. As i said earlier, most would cover the sills with sand. With wet harling or even tyrolean, a strip of polythene/anything,,,, covered with sand, and allowed to drape over, just enough to cover the front of the sill, that would protect it. They're messy jobs, and the more you can cover up,,, glass, window/doorframes etc, the less chance you have of problems with damage, scratching glass, staining etc. What you cant cover up,, clean off carefully, right away,, remembering that the sand in the mortar, can severely scratch glass.

    Roughcaster.
     
  7. self builder 123

    self builder 123

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    Hi Roughcaster

    Many thanks.
     
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