# Tips for priming raw mdf edges



## 9fingers (27 Jul 2011)

I have a project coming up to make a couple of radiators covers from mdf. I need to supply them primed ready for final colour.
Lots of raw edges to prime where slots cut to let the air flow. I'll be using mrmdf as I read this takes paint a lot better than the ordinary stuff

I see the pros using morrells and other pro products but these all seem to be sold in large quantities and are solvent based. I don't have a spray booth with all the necessary extraction etc etc just a Performance Pro (B&Q brand) HVLP sprayer - which works surprisingly well.

I need a primer/sealer that will produce an acceptable finish with an amateur HVLP sprayer ideally water based that I can buy retail from the sheds/screwfix/toolstation. Ideally not needing too much elbow grease between coats when sanding the routed profiles - I calculate that there will be around 60 metres of raw edge to treat!!

Any tips will be most welcome

tia

Bob


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## newt (27 Jul 2011)

Bob, I have used pva the stuff that you can obtain from the sheds or builders, it's used for sealing stone/brick backgrounds before plastering. Two coats then a light sanding, then either water or oil based primer. I did some tests on a sample piece first, I found it worked fine.


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## 9fingers (27 Jul 2011)

Thanks Pete, 
I hope that you are doing ok!

I've had another pva related suggestion too over on the other place
4 parts emulsion paint to 1 part pva

Bob


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## condeesteso (27 Jul 2011)

I agree with the pva idea, but have also found acrylic varnish (water-based) very good indeed on mdf edge, big benefit being it dries super-quick (but will likely need a couple of coats).
And could you keep it a secret that I have used mdf please?


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## mailee (27 Jul 2011)

I have tried the PVA method but found it so hard to sand down. I now use Morrells 2K primer and seal the edges of MRMDF by brushing two coats on it, it dries exceptionally wuick so can give it two coats almost one after another. It then sands down very easily to a superb finish ready for spraying. This is the solvent based one though as I never use water based. Although it is mixed with the hardener it will keep for a pretty long time if it is re sealed. Unmixed it will last for a very long time indeed...months and months. you only have to mix as much as you need so it is economical to use. Most of the pros use it so that must say something about how good it is. HTH. :wink:


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## bainsk8 (29 Jul 2011)

If you need the piece done quick then a couple of coats of shellac, 10 minutes to dry and its good to be painted over with whatever based paint you like. If you use white shellac, (clear) then it could even be varnished over too. When I worked on site I use to seal all the edges of MDF architrave and bullnose skirting with a shellac based product called Zinzer Bin Primer Sealer which has a white pigment added. really good stuff.

PVA is not such a good idea as it will sit on the surface unless it is thinned down with some water, but then it defeats the object as MDF could swell as a result of thinning too much. The other thing is if your using it for edges, then these areas are prone to knocks and PVA is too flexible and can also peel.


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