Painting and Waterproofing a MDF countertop

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Hi,

I am fitting a countertop in the bathroom which will sit under the sink. What is the best way to ensure that once finished it remains waterproof with a durable finish.

I was thinking of:

- couple of coats of MDF primer ('International Paints' branded)
- a coat of Oil based satinwood
- a coat or two water based satinwood.

I have used the above combination when painting MDF around the house to produce a good finish. The reason I use a coat of oil based paint is that it saves me from having to use 4 or 5 coats of the water based gloss. From experience the MDF soaks the water based gloss like a sponge, hence the ridiculous number of coats required. I finish with the water based gloss because of the non-yellowing properties as well.

Anyway, is the above enough to ensure a durable waterproof finish. Can I or should I used an acrylic based varnish to finish it off?

Any suggestions would be appreciated.

Cheers,

T.
 
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Hi

Painting MDF
With my projects I all ways use MR mdf ( moisture resisting) no mater what the project is, it is more dense which in turn will go a long way in giving you a better finish. I always seal plan mdf with a pigmented precatalyst lacquer and is applied by spray gun and is a professional product and not available from the big sheds. But if you don’t have the ways or the means with the above you can give the following a go and I think you will find it work extremely well, its all in the preparation.

• Plane all cut edges and I mean all cut edges even the edges you will not see, this process together with the sanding will go some way to help seal the cut edges as well as giving a more professional job.
• Fine sand (180 grit ) the cut edges at the same time remove the sharp edges.
• Thin 50% pva water proof wood glue with water and apply a thin and even coating to all cut edges and allow to dry fully, the adhesive will help give a water proof seal and cut down on the number of coats of paint.
• Once fully dry you can either apply iron on edging to the prepared cut edges or you can de-nib with a fine sand paper (320 grit) and apply your first coat of oil based primer to the cut edges only.
• If you want to go down the path of using iron on edging then do not de-nib the cut edges. Apply the edging making sure all the edges are well and truly fixed. It doesn’t mater about marking or burning the edging because when you have done all edges you will paint the edges once you have fine sanded the edging.
• Which ever path you want to go down at this stage you apply your first coat water based or oil based primer paint to all surfaces but applying by 100mm foam roller.
• De- nib between coats (320 grit) and apply finishing coats.

By going the extra mile on the edges you will stop the mdf act like a sponge and it is the edges that will let the side down and been the first part to allow the ingress of water.

You can get white iron on edging in 22, 30, and 50mm widths so even if you have rounded over the edges you can still apply edging. But to do a first class job that will stand head and shoulders above the rest, plane and fine sand all cut edges and seal with thin pva water proof glue.

Using a foam roller and making a little paint go a long way will give you a flat smooth finish flat finish without bush marks.

In the end you will have a project looking like a job in the town for all your hard work.
 

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