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  1. #1
    Join Date
    Nov 2008
    Location
    Ashfield Sydney
    Posts
    1

    Default plywood discolouration - mold or just stain?

    Hello kind people..

    I made some drawers and a work bench in the storeroom a few years ago. The top is tas oak and the drawers are hoop pine plywood.
    I sealed everything with Organoil exterior decking oil because I had a tin left over lying around - the space is a store room under the stairs after all. I, perhaps naively, thought anything designed for outdoor use would be fine for an indoor job like this.

    drawers.jpg

    The plywood is now showing some discolouration all over the place, small reddish blotches, anywhere that didn't have something sitting on top of it.

    close up 3.jpgclose up 4.jpg


    I first assumed mould and set about cleaning it, then sanding back with 80 grit with the intention of removing it all and applying a new sealer.
    Lots of sanding later and I can barely get into it.

    It doesn't look like the mould or fungus I'm used to seeing on wood. Any chance its some chemical reaction instead?
    It appears on the top plywood shelves as well. Hasn't appeared to get into the surrounding red cedar trims of the house...

    Any suggestions how to manage this would be much appreciated. Hoping I don't need to rip everything out and rebuild - the drawers are working fine still.

    Many thanks
    Stu

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  3. #2
    Join Date
    Feb 2006
    Location
    Perth
    Posts
    27,757

    Default

    You could try some Oxalic acid - valuable from Bunnings as Rust and stain remover

    https://www.bunnings.com.au/diggers-...eaner_p0960276
    They seem t0 only sell it in large packs and at $30+ its not that cheap for something that you might just want to try.
    Pity you are not close or I would just give you small amount.

    May sure you try it out on a "not very visible spot" in case it makes it worse.

  4. #3
    Join Date
    Jul 2008
    Location
    geelong
    Posts
    359

    Default

    Doesn't look like any kinda mould -More water stains. would expect them to sand out -depends how deep they have gone. Natural finishes tend to suck unless under perfect circumstances.

  5. #4
    Join Date
    Nov 2007
    Location
    melbourne australia
    Posts
    2,621

    Default

    I second the oxalic acid suggestion. Or some other form of chemical bleach.

    I caution against using 80 grit on soft plywood. You'll very quickly sand through the top layer of ply and then your staining issue will be the least of your problems.

  6. #5
    Join Date
    May 2003
    Location
    Central Coast, NSW
    Posts
    3,330

    Default

    Deck Cleaner is basically oxalic acid and will work just as well, but is much cheaper. Test in a small area first.
    Apologies for unnoticed autocomplete errors.

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