# MDF SEALER



## LESNPAM (8 Aug 2011)

HI ALL
im going to be making a couple of bedside cabinets in mdf finishing with a painted white gloss paint will it be sufficient to just seal the edges with mdf sealer proir to painting
regards
les


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## Ollie78 (8 Aug 2011)

MDF is a nightmare to paint.
To answer your question. No it will not be sufficient.
I have recently made a few built ins with MDF with simple rounded over edges on the doors.
During these builds I experemented with a few things.

1: Knifing putty (very fine filler used for fine filling car bodywork) 
This is very good at sealing the edges, but it is hard to sand so be very sparing with it. Time consuming but you can acheive a glass smooth egde.

2: Painting the edge a couple of times ( dulux MDF primer ,water based) then sanding back and painting the whole thing.
Not very good, caused more work for myself in the end.

3:Sand the edges with 320 grit sandpaper, just sort of polishes the edge smooth.
This worked surprisingly well, seriously reduces the excess paint absorbtion and reduces fluffyness ( is fluffyness a technical term? ).

I found that 2 coats of MDF primer, sand with 320 just to de nib, 1 coat of undercoat, 1coat of topcoat, de nib again and then final topcoat was a pretty decent finish. I was using Dulux trade waterbased paints.
Also either use very good brushes (Purdy are my favourite) or preferably a small roller on the flat areas.

Good luck
Ollie


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## mailee (9 Aug 2011)

I think you will find the best stuff for MDF edges is Morrells high build primer. It is a 2K paint and is not cheap but is brilliant on MDF. It does help if you use MRMDF as this isn't as 'fluffy'. I use two coats of it sanding between with 320 grit. (It dries in about an hour) and then over with the top coats, smooth as silk. I also spray the top coats on. It really is that good! :wink:


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## LESNPAM (9 Aug 2011)

HI
thanks very much for the info will post again when i have finished them 
best regards
les


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## Allylearm (4 Sep 2011)

Best tip is do not use MDF if edges are exposed and want a finish. Go for the Machine quality HDF this is finer particled and denibs best and lets the machined profiles be crisper and lets the paint seal the edges as the particles it is made up from are tighter nit so easier sealed so to speak.

The other way is curtain coating, but you still need better board and you need to denib. I have only seen this used in industrial setting, very high gloss finish is achievable with feed speed.


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## brimham (20 Sep 2011)

Hello i'm new to wood working and as a result i don't know some of the terms that are used. De nibing is mentioned a few times in this thread what's it mean?


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## CHJ (20 Sep 2011)

brimham":2wbsxtp3 said:


> Hello i'm new to wood working and as a result i don't know some of the terms that are used. De nibing is mentioned a few times in this thread what's it mean?


Removal of raised fibres, usually caused by moisture/solvents swelling fibres, usually done by light sanding.


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## brimham (20 Sep 2011)

Thanks for the quick reply. Today was the first time i have cut mdf. I made a jig to sit a guide bush in. 

"Removal of raised fibres, usually caused by moisture/solvents swelling fibres, usually done by light sanding."

Once again sorry for my ignorance, would the "nib" be the slightly raised edge around the cut, or would it occur on the face of the material?


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## CHJ (20 Sep 2011)

brimham":l579sv53 said:


> or would it occur on the face of the material?




Normally refers to raised grain or fibres on the cut/finished surface that can be felt/seen as a roughened surface after sealer or finish has dried.


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## brimham (20 Sep 2011)

thanks.


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## chippy1970 (20 Sep 2011)

When I get a spare minute I will take some photo's of my latest job, two sets of wardrobes with shaker doors 10 in total. I had all the exposed edges of the mdf edges edged with preparation tape. That way it can be painted with no problems whatsoever, its the first time I have seen this stuff and it looks good. Im sure the decorator will love it.


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## mailee (20 Sep 2011)

That's a new one on me Chippy? What is preparation tape? :?


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## RogerM (20 Sep 2011)

mailee":35l337e3 said:


> I think you will find the best stuff for MDF edges is Morrells high build primer. It is a 2K paint and is not cheap but is brilliant on MDF. It does help if you use MRMDF as this isn't as 'fluffy'. I use two coats of it sanding between with 320 grit. (It dries in about an hour) and then over with the top coats, smooth as silk. I also spray the top coats on. It really is that good! :wink:



Would you use the Morrells High Build primer for MRMDF if there were no edges to paint? An MDF panel set in a tulipwood or beech framed shaker door for instance?


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## chippy1970 (21 Sep 2011)

mailee":18es21nw said:


> That's a new one on me Chippy? What is preparation tape? :?


It's brown tape edging that can be painted just the same as the surface.

here it is cant really see it that well in the photos, my supplier does the edges square or slightly rounded mdf-wardrobes-t54351.html


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## mailee (21 Sep 2011)

Yes Roger I use the Morrells primer on all of it. I brush a coat on the edges and then once it is sanded pray the down I then give the whole lot two sprayed coats of the primer. You can actually just spray the edges by coating them each time the panel is sprayed front and back so they get four coats on the edges. But I like to use it like a stopper to make sure. Two coats is sufficient for MRMDF and it sands down very easily so is no problem. 

I have never heard of the tape Chippy. Is it self adhesive or is it glued on and whats it made of?


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## chippy1970 (21 Sep 2011)

Hi Alan , its like some sort of paper tape they put it on with a huge edgebanding machine then I had it slightly rounded put you can leave it with a sharp square edge if you want.

Heres a better photo


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## mailee (21 Sep 2011)

Ah I see now. It has to be fitted with a machine then? I have seen it before but didn't realise what it actually was.


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## Allylearm (25 Sep 2011)

chippy1970":4a3ujep0 said:


> Hi Alan , its like some sort of paper tape they put it on with a huge edgebanding machine then I had it slightly rounded put you can leave it with a sharp square edge if you want.
> 
> Heres a better photo



The issue with taping is you have to watch for expansion due to moisture absorption on the edge and the other issue is saw chatter from misaligned teeth on saw cut. As such the better edge banders, they have a trim cut prior to gluing the edge on with the scraping the top and bottom face of board the most important aspect for finish.

In hand finishing it is worth thinking about the edge preparation prior to ironing or gluing your tape on prior to trimming.

For flush edges the tape is good idea, but for shaped edges denibbing is requirement or unless you solid wood edge the profile on with Edge bander or by manual method saves time in painting or matching grain/timber finish.


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## mailee (25 Sep 2011)

I see, so it's not really a DIY sort of application to get a good edge. I shall stick to priming the edges as my doors are often rounded or ogee profile. Thanks for all the info on it though guys, at least I know what it is now. Thanks. :wink:


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## chippy1970 (25 Sep 2011)

Allylearm":1oih0ac0 said:


> The issue with taping is you have to watch for expansion due to moisture absorption on the edge and the other issue is saw chatter from misaligned teeth on saw cut. As such the better edge banders, they have a trim cut prior to gluing the edge on with the scraping the top and bottom face of board the most important aspect for finish.



Yeah they have a pre-miller on their edgebander, state of the art by the looks of it take a look http://www.wrightscarpentry.com


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## Allylearm (6 Oct 2011)

[/quote]

Yeah they have a pre-miller on their edgebander, state of the art by the looks of it take a look http://www.wrightscarpentry.com[/quote]

The trick is glue application and how you trim, the buffers are a bit of a gimic to be honest. I am sure the one shown and rest in the -£35k region can edge up to 60mm. I was told recently the market is applying 2mm finished edge tape but the Europeans are going for 1mm now to save costs.


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## bosshogg (6 Oct 2011)

Sheesh, all this about sealing some MDF boards. First apply some pva glue alang the edges with yir finger min, then thin down some mare pva wee a dod 'o' watter and paint ower thae boards...sorted
Cheers...bosshogg  


> A true friend stabs you in the front. Oscar Wilde :|


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## Allylearm (6 Oct 2011)

So u do not trim it, u must have steady hands


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## imasinner (5 Nov 2011)

I just created a new post for the preparation tape that was mentioned above, we buy a white coloured one and edgeband it on directly ourselves.


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## studders (5 Nov 2011)

Hmmm tricky one.

Yes the link to the paintable edge banding is helpful, even though 'tis you selling it - which isn't made crystal clear.
How ever, it's a useful link but, I think you've made your point now, any further links to it would definitely be spamming in my view.


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## studders (5 Nov 2011)

bosshogg":30nyhhum said:


> Sheesh, all this about sealing some MDF boards. First apply some pva glue alang the edges with yir finger min, then thin down some mare pva wee a dod 'o' watter and paint ower thae boards...sorted
> Cheers...bosshogg
> 
> 
> > A true friend stabs you in the front. Oscar Wilde :|



That's OK if you're using Oil based paints I think, so far as I know, and as personal experience has shown, 'tis not a good idea if you're using water based ones, which, apparently, we will all have to before too long.


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