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Sealing the rough edge of MDF

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Manks

Original Poster:

9,856 posts

126 months

Friday 5th October 2012
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Does anyone know how to seal the edge of MDF board so that when it is painted it doesn't appear rough, please?

jke11y

2,447 posts

141 months

Friday 5th October 2012
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My guys use Ronseal wood filler on site; gives a decent finish when painted, very similar to the painted face in all honesty.


Rosscow

4,499 posts

67 months

Friday 5th October 2012
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Yep, it'll need maybe 4 coats (2 primers, 2 top coats) but it's essential to rub down between coats.

You'll actually get it quite smooth if you persevere smile

Simpo Two

65,076 posts

169 months

Friday 5th October 2012
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PVA?

Rosscow

4,499 posts

67 months

Friday 5th October 2012
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I wouldn't, too messy. Just give at an extra coat or two of high build primer with rub down between coats.
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plug

1,101 posts

142 months

Saturday 6th October 2012
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Use moisture resistant (green) mdf, its not so fluffy on the edges, or spread a thin layer of 2 pack filler along edge before painting.

Donboy

71 posts

45 months

Saturday 6th October 2012
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X 2 for PVA ..

Dr Mike Oxgreen

2,541 posts

69 months

Saturday 6th October 2012
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Can't you just use the edging tape that you iron on, then trim with a knife?

singlecoil

22,614 posts

150 months

Saturday 6th October 2012
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Use the same paint as you do for the face, just apply extra coats and rub down between coats. Use water based paint for best results and least pong.

m4ckg

614 posts

95 months

Saturday 6th October 2012
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the edge needs 'polishing' with sandpaper, use a couple of different grades and finish with some wet and dry or something like 240 grit

Rosscow

4,499 posts

67 months

Saturday 6th October 2012
quotequote all
PVA and filler really not needed - just rub down between coats and apply a couple more coats!

Simpo Two

65,076 posts

169 months

Saturday 6th October 2012
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Six different answers - not bad for a humble piece of MDF!

singlecoil

22,614 posts

150 months

Saturday 6th October 2012
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Some of the answers might be from people who do a lot of this stuff. The trick is to figure out which those might be.

Simpo Two

65,076 posts

169 months

Saturday 6th October 2012
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Such is the wonder of forums. However, it does not mean that suggestions from non-kitchen-making professionals will not work. It is only a piece of MDF after all, not carved lace by Grinling Gibbons.

singlecoil

22,614 posts

150 months

Saturday 6th October 2012
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Has anyone said that any of the suggestions wouldn't work? If they did, I must have missed it.

Simpo Two

65,076 posts

169 months

Saturday 6th October 2012
quotequote all
My mistake, I took your reply to mean that your answer was best because you do a lot of this stuff.

Henry-F

4,759 posts

149 months

Sunday 7th October 2012
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Well PVA isn't a very good suggestion because it never sets hard enough to sand without tearing.

Filler, especially 2 part filler will be far too hard and likely cause high spots with the softer MDF. It is also hard to sand.

The best way is to sand the edge down then paint with sanding sealer or primer. Allow to dry then sand flat. If necessary repeat. The sanding sealer in particular penetrates into the MDF hardening it and stopping the fluffy edge when sanded back.

Filler doesn't penetrate the MDF so once sanded through you still have a problem.

As has been said already with a bit of thought and being prepared to wait for coats to dry you can achieve an excellent edge on MDF.

Henry smile


m4ckg

614 posts

95 months

Sunday 7th October 2012
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I've been helping out at a company that makes furniture for pubs etc etc and polishing with fine sandpaper is the.prefered way

Manks

Original Poster:

9,856 posts

126 months

Sunday 7th October 2012
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I should add that the rough edges will sometimes fall in difficult to sandpaper places. There is a risk of roughing up other surfaces in the process.

singlecoil

22,614 posts

150 months

Sunday 7th October 2012
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Manks said:
I should add that the rough edges will sometimes fall in difficult to sandpaper places. There is a risk of roughing up other surfaces in the process.
Then use a Stanley knife blade held verticallyish to the surface and scrape it instead. With a bit of care you should be able to smooth the required surface without affecting other areas or cutting yourself (that won't matter so much if you are using red paint).

If you can't get to the edges in question at all, then you will need to redesign the product until the edges aren't visible.