MDF Window Board, Got Wet in One Spot Whilst Untreated

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Sheepdisease
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MDF Window Board, Got Wet in One Spot Whilst Untreated

Postby Sheepdisease » Tue Aug 14, 2018 8:12 pm

Hello everyone, I am having to deal with an MDF window board which got wet in one spot.

It's times like this that I hate working with MDF..

I sanded the board back flat, applied acrylic resin based combined primer and undercoat several times, then sanded flat again. I ended up back at the beginning with the same amount of bare wood where the wet patch was with the wood rising in that specific area.

Please tell me there is an easier way or a better approach (keep in mind that this board is fixed to the wall and plastered in)?

JonR
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Re: MDF Window Board, Got Wet in One Spot Whilst Untreated

Postby JonR » Tue Aug 14, 2018 9:10 pm

I would chisel the raised area back below the surface and then fill with a 2 pack filler sand smooth and start over with the painting process.

Sheepdisease
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Re: MDF Window Board, Got Wet in One Spot Whilst Untreated

Postby Sheepdisease » Tue Aug 14, 2018 10:40 pm

That might be the best idea, if I keep sanding back without doing this, will I eventually get the desired result?

JonR
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Re: MDF Window Board, Got Wet in One Spot Whilst Untreated

Postby JonR » Tue Aug 14, 2018 11:20 pm

Maybe, but acrylic paint is water based and it seems it keeps swelling the mdf fibres and if its a cheap mdf it will be quite fluffy below the surface compounding the problem. Medite and MR Medite are much denser and better at coping with a bit of moisture. I don't use standard mdf for anything always medite/MR mdf.

9fingers
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Re: MDF Window Board, Got Wet in One Spot Whilst Untreated

Postby 9fingers » Thu Aug 16, 2018 8:30 am

Use something like zinnser primer to seal the surface. There is a good reason why we have used oil based paints for decades. So many problems arise with water based rubbish.
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