Edge Sealing on MDF?

[Chems]

I know there is a thread just below about this but I thought I'd ask this question so it can be found easier later on.

Now according to that thread you need to sand to 120 grit, then apply PVA glue mixed 5part water 1 part glue then prime and paint.


Now I've sanded to 320 on a planed surfaces and then primed about 2 coats and now given 2 coats of colour. The edges still look rough.

Is their still time for me to mix up some PVA glue and treat the edges both cut and routed?

 

[Oryxdesign]

Did you sand between coats?

 

[jasonB]

The PVA solution won't soak in.

Did you rub down between coats particularly after the first, and what MDF are you using?

Jason

 

[Chems]

I have rubbed down between coats.

I'm using Caberwood Standard MDF.

So just keep applying the coats and rubbing down between coats?

 

[Oryxdesign]

I'm sure somebody will come along and tell you that you should have used mrmdf, the problem with the standard stuff is that the paint will just keep soaking in and leaving you edges rough. You could experiment on a bit of scrap to see if the pva mix will seal or perhaps try some mdf primer. Once you get it sealed you'll be fine.
Is there lots to be done or was it a small project?

 

[wizer]

On a recent bookcase project, I applied a few coats of watered down pva to the edges and sanded down between coats. Then sanding down again between each coat of paint. Standard B&Q MDF

Worked well for me, the edges are as smooth as the surfaces.

 

[Chems]

But after I've already started painting Wizer?

 

[Steve Maskery]

I've not actually tried this but.....

If you feel you have noting to lose, I'd be inclined to mix some fine filler (I don't think you can beat Tetrion) with PVA and water to a thick cream and rub it into the edges. The PVA should help it to stick and Tetrion sands beautifully.

Maybe you don't even need the PVA.

If you try it, please let me know!

S

 

[compo]

Hey Chems, know how you feel ](*,)

I seal all edges with slightly diluted pva, and use a high build primer, simple.

Seeing as you've put top coat on I'd suggest you use car body filler or even better, stopper (a very fine filler that can be applied as thin as paper and sands easily). Then sand and recoat as required.

Personally I'd not use Tetrion, it's just not smooth enough and may not stick to your applied finish.

Just the way I do it and it works for me. Tho like many things in life, there's lots of different approaches.

However, as we all know - Opinions are a bit like belly buttons... we've all got one!

Sean

 

[Steve Maskery]

Compo
Why do you think that Tetrion isn't smooth enough? It comes out like glass, or at least as smooth as MDF. I'm sure I've not got the wrong product. Perhaps there is an Interior and Exterior version?

I agree there may be an adhesion problem if the MDF already has a finish applied.

S

 

[compo]

Hi Steve

Tetrion is good, but not in a furniture making sense. Plus it's too brittle to apply thinly.
Yes it can be as smooth as glass/mdf although that can be a long way from flat.
A bit like painting over sand - albeit very fine sand!
It is always better to have a flat, smooth surface to finish onto.

Just my opinion, of course

 

[Steve Maskery]

OK. Actually I'd not thought of the brittleness. But I bet the PVA would ameliorate that, wouldn't it?

I think I might have to experiment.

S

 

[imasinner]

I only water my PVA down a little (10-20%), so i can apply it better, this glues up the edge really well, and then a light sanding with 120 grit paper will smooth it out.
You may have over sanded the weakly glued edge, thats why it furred up?

Try this MDF painting guide

www.builtinsolutions.co.uk/painting

 

[Krysstel]

Does anyone use sanding sealer instead of PVA/water mix ?