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To undercoat or not

Discussion in 'Decorating and Painting' started by ithomson, 6 Oct 2010.

  1. opps

    opps

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    Never used it but why would silicone cause drag, I'd have thought it would reduce the coefficient of friction and result in fisheyes.

    Bar exterior wood work I only use gloss every 3 years or so.

    Isn't the term self undercoating just marketing? After all eggshell and satin wood don't require u/c.
     
  2. Growler

    Growler

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    Nearly forgot. Another thing that causes drag is "candle wax". The aftermath of burning candles on your woodwork. Not just soot deposits on your ceiling.

    Yes, it is "self undercoating", and no, it isn't marketing. It really is "self undercoating" when used correctly.
     
  3. ic1927

    ic1927

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    Yes it's the same stuff. Only seen it in white.
     
  4. opps

    opps

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    I had to re-eggshell a unit that i last painted 10 years ago.

    The client wanted to go from a deep yellow to a cream so i decided to use a coat of dulux trade white oil based undercoat first to obliterate the colour- bad move. Even with paint driers the undercoat was still shinny after 2 days and although it was nearly hard enough to denib it the dust was a mare to brush off.

    Wish I stuck with waterbased primer... it might be crap but atleast it is sandable
     
  5. Growler

    Growler

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  6. opps

    opps

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    Hi growler

    I used the dulux trade stuff for years until they changed the formulation one too many times. I switched to the leyland stuff earlier this year because the dulux trade stuff just became impossible to sand back.

    i had been using it as a primer for mdf and i'd sand it back with 180-220 silicone carbide to reduce grain swell. The intended sanding rate was such that the MDF was flatter than when it left the factory. The last formulation tweak made this impossible as it would overheat and clog the paper, both when hand sanding using the National Abrasives brand and machine sanding with Titan 2 paper on a Festool rotex with dust extraction.

    In the end I switched to the inferior Leyland acrylic primer, a third of the price and easy to sand, colour obliteration is poorer however.

    I still use Dulux trade eggshell though and would never use the leyalnd version.
     
  7. Growler

    Growler

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    If you were to be using it over the units you described, you'd only need a light touch over with 400.
     
  8. opps

    opps

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    ??????

    A light hand sand with 400g of the Dulux Trade acrylic would do very little. At best it might soften the peaks on the tramlines but it wont do anything for the grain swell or the scratch marks from the factory sanding.

    I used to be able to use 400g on my rotex with an interface pad but that was prior to the formulation tweak.

    I am speculating here but the leyland seems to have a lower latex content and thus sands more easily.
     
  9. Growler

    Growler

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    You painted it 10 years ago and you can't undercoat it because of tramlines that you'd make?
     
  10. opps

    opps

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    I think we are out of sync here.

    The unit that I repainted was the one where I used the oilbased uc, the UC that was only barely sandable (after 2 days) yet still tacky meaning that the dust was difficult to remove.

    When i referred to waterbased uc as being crap i meant that it tramlines more more oilbased and the obliteration is inferior.

    The later references to the dulux vs leyland were a wider comment on the sandability of the former.
     
  11. Growler

    Growler

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    So , use Dulux Trade quick drying and just go over it with 400.

    Or is that a huge problem for you as well.
     
  12. opps

    opps

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    Not sure what your problem is.

    I was trying to warn people that the 2010 Voc oil undercoats are very different to the pre2010 undercoats.

    You, reasonably, suggested a paint, one that I had used for over 12 years until this year. I explained why I have stopped using that particular paint and your advice is to... use that paint!

    Err... thanks
     
  13. Growler

    Growler

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    Your welcome.
     
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