Spray, roll or brush MDF?

Discussion in 'Decorating and Painting' started by Yorkshirebloke, 24 Oct 2018.

  1. Yorkshirebloke

    Yorkshirebloke

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    Hello all,
    Been doing some reading and searching but couldn't quite find what I was after.
    Basically how would you choose to paint MDF? I'm fitting a couple of new window sills (one is 9 foot by 2 foot in a bay window) so I can paint it before or after fitting depending on what you'd suggest.
    Thanks all
    Alex
     
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  3. Buck_68

    Buck_68

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    This youtube is a decent watch IMO

     
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  4. Yorkshirebloke

    Yorkshirebloke

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    Ah thanks pal a good video indeed.
    Fairly straight forward too.

    The only reason I was even entertaining painting it, is because I used to be a car painter. So I've got all the equipment I need, that is if my gun would take the paint viscosity. Is it ordinary gloss just thinned down do we know or is it specific to painting?

    Cheers
    Alex
     
  5. opps

    opps

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    As someone who used to work week in, week out, hand painting MDF wardrobes I cringed whilst watching that video. If I provided that level of
    finish the cabinet makers would never have recommended me to their customers.
     
  6. opps

    opps

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    If I spray MDF, I use precat primer. Being solvent based it doesn't raise the MDF grain and is a dream to sand back. I use a DA sander with an interface pad and 320 grit paper. As a side note, I seal end grain with 2 or three coats of bush applied acrylic primer, sanding between coats with 150 grit.

    In an ideal world I would then spray 3 coats of acid-cat top coat (sanding between coats). AC is pretty evil to lungs though so I wouldn't recommend using in a house where there are other people around.

    In your case, I assume that the boards are pre-primed. After preparing them do you plan to use waterbased or oil based gloss?

    I can spray oil based gloss with my 3 stage Fuji HVLP but I need to add Owatrol to it (and some white spirits) to get the correct viscosity. The big downside to spraying OB gloss is the slow drying sticky overspray.

    I have never sprayed waterbased gloss. Given that it is harder to atomise waterbased paints, you'd need Floetrol and water, and may even need to heat the paint slightly. Airless sprayers are better suited to working with waterbased paints.

    You also need to consider the time and costs of cleaning the gun though.
     
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  7. Yorkshirebloke

    Yorkshirebloke

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    Ahh excellent advice cheers!
    Time and costs of cleaning the gun is free as it were as this wouldn't be for a customer as such, just for me and my house.
    The fumes again I'm not too bothered about as there is pretty much only me there working on it. The main things I would be painting though would be the skirting boards and window sills, so they could all be painted in the garage before fitting. Whilst it's not dust free, it's the best I've got.
    As for pre primed, I haven't bought any of it yet so I'm all ears for any opinions. I would have to prime the window sills as I need to make them myself rather than buy them in.
    As for the gun, I'm fairly certain my devilbiss primer gun would cope with the viscosity. The high build primer we used to use was like syrup lol
     
  8. opps

    opps

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    MDF skirtings are normally pre-primed. TBH, I hate painting them. I have no idea which acrylic primer they use but it is a mare to sand flat.

    I am not a fan of MDF skirtings/architraves. Most of the houses that I work in have timber rather than MDF but on the odd occasion where they do have MDF, after a few years the architraves have loads of chips/dents. I warn the clients that the 2 pack filler that I use to fill the dents will break away the next time that the hoover head (or whatever) hits it again.

    Years ago I worked for a cabinet maker (as an assistant) and he used to make me brush some kind of epoxy on to all routed MDF edges. The stuff was rock hard and penetrated quite deep into the "grain". It took ages to sand flat but the edges stood up to a lot more abuse than the waterbased primed MDF.

    In-spite of my dislike of MDF skirtings and architraves, I have no problem with MDF window boards/sills. If you are willing to pay a little more, I'd suggest the moisture resistant MDF. It is harder to cut and your router will need to work a bit harder to create bullnoses/profiles but it is much less prone to swelling should, for example, you leave the window open and the rain comes in or some one over waters a plant pot on the window sill.

    In the event that you do not want to buy 5L of precat, I use leyland Trade acrylic primer/UC to hand prime MDF. You can get 5L for about £20. I don't buy it because it is cheap, I buy it because in many respects whilst it is inferior to the likes of Dulux Trade acrylic primer/UC it is the only acrylic that I have found that is easy to sand back. If hand sanding, I use 180 grit silicon carbide paper (preferably the one made by National Abrasives- it clogs less and doesn't go blunt as quickly as brands such as Sait).

    You mention gloss, have you considered using eggshell? It is far more forgiving with regard to dust contaminates and surface imperfections.

    Finally, if you do go with oil based paints, terebene will speed up the curing process.

    https://www.amazon.co.uk/Rustins-Paint-Driers-Terebene-250ml/dp/B00N4ZZBBQ

    BTW the above link is probably much more expensive than your local decorators' merchant. From memory, I pay about £7 for a bottle. It lasts for ages though given that you only add a tiny amount.

    Sorry, am having a quick pint after a stoopidly long day, feel free to ask if any of the above reads like the ramblings of a slightly less than sober but not yet pee'd crazy man.
     
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