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Protecting spray-painted (PU/oil-based paint) MDF doors

Discussion in 'Decorating and Painting' started by MasterMark, 9 Sep 2019.

  1. MasterMark

    MasterMark

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    Hello all!

    I had some replacement MDF doors made for me for a sideboard refurbishment. They seem to have come to a nice finish, in a dark green paint. The MDF was sanded & primed first.

    The company used a polyurethane/oil-based paint (Sayerlack, I believe) in a satin (20% gloss) finish.

    I understand that oil-based paint cures considerably more quickly than water-based - the doors were finished 3 weeks ago, but on hanging them, the finish does seem to pretty "delicate." I had some clear lacquer/varnish at home (Polyvine), but when I called them they said it would only work on water-based, not oil-based, paint.

    So my question - is they any sort of varnish/lacquer that I can apply to the doors to make them a little more resistant? Any suggestions would be much appreciated!
     
  2. Notch7

    Notch7

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    if the doors were sprayed with Sayerlack 2k PU that is one of the hardest finishes available.
    I dont know how long it takes to reach full hardness, I would have thought 2k products would crosslink quite quickly, but maybe full hardness takes a while to achieve.

    by delicate, what do you mean? -easy to scratch / mark or easy to chip?

    Polyvine will be softer than PU.
    I would be a bit nervous of overcoating, there is a risk of the coating delaminating in the future. Also you will alter the colour and sheen levels.

    if you can find out the product used you might be able to get a bit if information from the technical data sheets here:

    https://www.movac.co.uk/wood-finishes/interior-wood/water-based-coatings/
     
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  3. MasterMark

    MasterMark

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    Thanks, Notch7, appreciate the response. I've checked with the spray-painters if that's the exact finish they used and see what they say.

    But to answer your question, yes, it seems to mark/scratch quite easily. I have lacquered kitchen doors from a Germany company, and they seem much, much more resistant. I feel like I'm going to have be super careful with these doors.

    And thanks for the link, though I confess to being clueless - I thought PU paints were by their definition oil-based, but seems they are also water-based. So maybe they used a water-based PU rather than oil-based PU.
     
  4. Notch7

    Notch7

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    Car paint is now water based PU.

    Im not sure of the chemical difference, my understanding is that both solvent and waterbased PU finishes have iso-cyanate in them.

    The solvent ones arent really oil based -that terminology is used for alkyd paints used for brushing mostly....like good old Dulux!
     
  5. opps

    opps

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    Dark colours often take much, much longer to fully cure.

    I recently sprayed some furniture with a very dark grey/brown 2K cellulose paint. Although it was touch dry in 30 mins, it was much softer than than a pastel colour would have been.

    Years ago I hand painted a 7m fitted book case in a dark green for a customer. Due to lack of space I took the shelves home, painted them, left them to cure for a week and then stacked them to return them. The journey was 30 minutes. The shelves stuck to each other and had to go back to mine to repaint them all. For the next 2 or three months, if you ran your finger nail over the surface, you were left with a lighter green. The paint wasn't damaged, you could wipe the lighter marks away, after the 3 month period all was fine.

    I suspect that your doors haven't fully cured yet. The problem arises because the base colour is very light and accordingly requires a lot of pigment when a dark colour is selected. Lots of pigment seems to massively increase curing time. I am assuming that (as hinted at by Notch7) you are experiencing scuff marks rather than scratches/chips.
     
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  6. MasterMark

    MasterMark

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    Thank you, Opps, that's actually very reassuring. And yes, as you and Notch7 both note, it's more scuffs than scratches and chips. The cabinet's now in place, and I have the advantage of no kids running around so it should be fine to sit there for a couple more months to cure without additional damage. Thanks again!
     
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