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New Indian Sandstone patio

Can anyone help me please? What are these marks on my new patio and will they go away? It was laid at the beginning of April 2021.


  • steephillsteephill Posts: 2,636
    It is a phenomenon called efflorescence which is simply the natural salts and minerals in the stone being deposited on the surface as water within the stone evaporates. You can try gently brushing it off on dry days but it will probably continue for some months yet.
  • Has this occurred because we have had frosty nights during April, followed by warm sunshine during the day?
  • tui34tui34 Posts: 2,718
    We call it saltpetre here.   Common occurence after tiling.  To eliminate these salts, you just keep washing/rinsing with water only and mopping dry.  Takes a while but it does eventually go.
    A good hoeing is worth two waterings.

  • tui34tui34 Posts: 2,718
    And here it is!!
    A good hoeing is worth two waterings.

  • Thank you I am hoping it will disappear with frequent washes and will lessen overtime as the slabs weather. Will keep working on it in the meantime.
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