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  1. #1
    Join Date
    Feb 2007
    Location
    port macquaire
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    Default Black marks on the new outdoor setting

    Thanks for the advice on finishing the deck Have ordered Spa'n Deck Next weeks job to do the finishing!!!
    We bought a lovely hardwood setting to use on the the deck, and it has been delivered. It has been on the deck for three weeks and is getting some horrible black marks .It is made locally from locally milled timber - not sure what the timber is, and we have asked the manufacturer to return and fix it but are wondering what causes these black marks.
    The setting was oiled with Wattyl deck oil prior to delivery so it was bought ready to use. It hasn't had anything spilt on it. There are no trees adjacent to the setting.

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  3. #2
    Join Date
    Feb 2007
    Location
    port macquaire
    Posts
    6

    Default

    Footnote - the decking also has the black marks on them.

  4. #3
    Join Date
    Aug 2003
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    Default

    By the looks of it, it wasnt seasoned timber thats why it is cracking, the black is the tannin being released from the green timber.

    Al

  5. #4
    Join Date
    May 2006
    Location
    sydney
    Age
    64
    Posts
    364

    Default

    This is caused by a electrolysis reaction between Tannin acid and metal. During the sanding process, small deposits of metal grit get lodged in the open grain. In a short period of time ,the tannin acid reacts with and metal and stains that infected area. It is common when new decks are built and iron fillings from roof works are on the deck. It is more common with eucalypti spices. The piece needs to be washed with a deck cleaner that contains oxalic acid.

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