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Paint stains/reaction on water based exterior top coat

Discussion in 'Decorating and Painting' started by Deansplit, 22 Sep 2012.

  1. Deansplit

    Deansplit

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    I have painted bare mahogany double doors and am getting a reaction. Here's the details:

    1 coat of oil based aluminium primer (advised to prevent oils seeping through to top coat), 2 coats white Dulux Weathershield, self undercoating, followed by 3 coats purple Dulux Weathershield.

    When I did the 3 purple coats after drying overnight, everything was fine, no reactions or stains that I have now started to appear. The stains initially looked like spores.. white wispy tiny lines dispersing from central points, almost like the pattern damp/fungi can create on a wall. They rubbed off easily when touched, but the next day they were back, in similar areas (from what I can recall), but also now more of like markings as if someone had chucked milk on my door, with clear indications of running/drips. I washed it off again in one area and painted over that area again to see if it came back... it did! And now in other areas.

    I'm absolutely gutted and the finish is brilliant and was very pleased with it. The weird thing is, it seems to be only in areas, nothing at the top halves, quite a bit on the ledges of the architrave and in the corners/creases of the architraves, but this morning, all over one of the inset panels!

    We 'do' live right on the seafront in Northern Ireland so could the salt be having an effect? Although the original pitch pine doors were painted with the very same paint and was fine. Other points to consider is the temperature has dropped a fair bit over the last few days (especially at night) which coincided with the stains (but then the paint was dry after an hour so can't see this being an issue). I did also use a small brush before any of this started happening to just touch in areas where it was still a bit patchy/not full opaqueness, and the brush I used had been used that day for oil based paint in another room, but I obviously washed it out – at first, again, from memory, I thought the areas which first came up were where I'd used this brush, but now that an entire inset panel has come up it rules that out because I certainly didn't paint that with the small brush, it was just small areas like the sides of the architrave etc.

    Any help much appreciated, here's the pics (note also on the pic of the full lower panel effected, quite strange, there seems to be clear line across the entire bottom left corner where it's not bee effected!??):

    http://www.diynot.com/network/Deansplit/albums/13580

    (had trouble uploading the pics into this post so hoping this link works...?)
     
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  3. dcdec

    dcdec

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    When you say white self undercoating what do you mean?

    I don't think its part of this problem but you should always apply the appropriate coloured u/c for topcoats, purple wouldn't be white probably a light to mid grey i'd guess.

    So apart from the ali primer its all water based?

    The problem is we (or at least i) don't know much about defects in WB paints as its a new area for us (me). It looks a bit like blooming which can occur in low temps, high humidity or exposure to atmospheric pollutants but not sure if it applies to WB. The salt would be classified as a pollutant, sounds weird but have you tasted it? put a bit on your finger and 'tounge it' and be sure to spit it out.
    Also dulux have a bit of a reputation for pigments separating in some of their weather shield colours, any problems with streakiness?

    Unless any of the other guys have a suggestion i'd say you need to get on to Dulux for a specification because of the conditions your applying the paint in.
    Be interested to hear what they say, can you update us when you have spoken to them?
    Good luck with it
     
  4. ic1927

    ic1927

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    That looks very much like surfactant leaching, a problem associated with a drop in temperature and condensation settling on the surface the same day as it has been painted. Dark coloured weathershield is more prone to this because the darker the colour the more surfactants contained within the paint. It may weather off in a month or so, to remove it gently wash it with out scrubbing, but I'd leave it a while and see if it weathers off, this leaching will not compromise the paint. Don't use dark colours in weathershield if the temperature is likely to drop significantly in the evenings.
     
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  5. dcdec

    dcdec

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    I wondered about that but dont think surfactant leaching happens with WB paints?
     
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  7. ic1927

    ic1927

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    Surfactant leaching occurs in latex paints, never known it to occur in oils, do oil paints contain surfactants?.
     
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  8. dcdec

    dcdec

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    No, your right, its only WB, i'm getting muddled up between the two.
     
  9. ic1927

    ic1927

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    Cheers dcdec, I've only come across this problem a few times and only with dark coloured masonry paint. It happened to me last year and it was a nightmare trying to convince the customer that it would weather off, it did within a month or so much to my relief.
     
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  10. Deansplit

    Deansplit

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    Wow, thanks guys, that's probably the best news I could expect anyway. I did do the lick test but it's such a fine stain I could barely get enough on a finger! No salt taste anyway, so hopefully this surfactant issue is the cause and as you say, will weather off, and boy do we get the weather in NI to deal with that!! :) Rain due tomorrow I think so will see what happens.

    Cheers
     
  11. DIYnot Local

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