# Carpenters or builders with experience working with MDF.



## evildacat (Mar 17, 2013)

I have had a desk/hi-fi thing custom made due to the small amount of space I have where I live. I would like to know how to protect/seal the desk part from water or other liquids as I know it absorbs.

Yes I have looked on site and there are quite a few different approaches I have come across, all I want to do it protect the top of the desk and the edges from water damage as much as possible.

I don't want to paint it any colour just a clear finish that won't damage the MDF. I've been told the biggest issue will be protecting the corners and edges from water damage (where it was cut and sanded) and have been given  numerous solutions but I obviously do not want to damage it as they cannot all be the right way to go about it.

Any help from someone who has done such work would be appreciated.


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## sim667 (Mar 18, 2013)

MDF is evil and it should all be burnt.

Apart from that I have no idea, sorry.


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## eoin_k (Mar 18, 2013)

Best you don't burn it - the fumes are probably really toxic.  Danish oil is probably an easy option that should help.


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## Mrs Magpie (Mar 18, 2013)

Acrylic varnish. It can be matt or gloss.


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## Bassism (Mar 18, 2013)

I love acrylic varnish or yatch varnish will do


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## evildacat (Mar 18, 2013)

Mrs Magpie said:


> Acrylic varnish. It can be matt or gloss.


 
What about the corners been told I will need use some kind of filler to seal it and then sand it down.

not http://www.agwoodcare.co.uk/Item/rustins_mdf_sealer?gclid=CPCPyrL1hrYCFYbHtAodvhoA4Q then?


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## xes (Mar 18, 2013)

if it's good enough for a mobile phone, it's good enough for your puny wood.


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## Hocus Eye. (Mar 18, 2013)

I read somewhere that MDF is the asbestos of the future. That it is that it is extremely dangerous. But the fact being denied by the industry for several years before being admitted after many people were made ill or died from it.

MDF is held together with formaldehyde resin so that when it is cut or sanded lethal dust is created. Even months after manufacture items made from MDF emit urea formaldehde vapour.


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## Mrs Magpie (Mar 18, 2013)

evildacat said:


> What about the corners been told I will need use some kind of filler to seal it and then sand it down.
> 
> not http://www.agwoodcare.co.uk/Item/rustins_mdf_sealer?gclid=CPCPyrL1hrYCFYbHtAodvhoA4Q then?


Well, when I stick stuff to wood, MDF or whatever I use PVA which acts as a sealant and doesn't cause any problems when it's varnished with acrylic varnish. Let it totally dry first, say 48 hours, before you put on the varnish.


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## peterkro (Mar 18, 2013)

I presume it's bare MDF if so it'll be similar to worktops in commercial situations anybody worth their salt will seal the undersides of worktops with polyurethane to prevent the soggy cardboard syndrome caused by MDF being soaked.


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## weltweit (Mar 18, 2013)

evildacat just how much water are you expecting in your office?


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## evildacat (Mar 18, 2013)

weltweit said:


> evildacat just how much water are you expecting in your office?


Its not for an office its in my room, just want to protect it against spills as MDF absorbs water and just been told to many different ways to do it is all.


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## ViolentPanda (Mar 18, 2013)

evildacat said:


> I have had a desk/hi-fi thing custom made due to the small amount of space I have where I live. I would like to know how to protect/seal the desk part from water or other liquids as I know it absorbs.
> 
> Yes I have looked on site and there are quite a few different approaches I have come across, all I want to do it protect the top of the desk and the edges from water damage as much as possible.
> 
> ...


 
You can buy MDF sealant at any of the big DIY sheds, in cans that say "MDF sealant" on them.   I've used it to seal MDF for painting. It's basically a "size", sealing the surface enough so that you can put a finish on it.
Once you've sealed it you can, if you want, then varnish over it to give it a more durable/solidly waterproof finish. I'd recommend an acrylic varnish. The smell isn't as oppressive, and it washes out of the brush or roller much easier than oil-based varnishes.


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## evildacat (Mar 19, 2013)

ViolentPanda said:


> You can buy MDF sealant at any of the big DIY sheds, in cans that say "MDF sealant" on them.  I've used it to seal MDF for painting. It's basically a "size", sealing the surface enough so that you can put a finish on it.
> Once you've sealed it you can, if you want, then varnish over it to give it a more durable/solidly waterproof finish. I'd recommend an acrylic varnish. The smell isn't as oppressive, and it washes out of the brush or roller much easier than oil-based varnishes.


 
I have obviously seen these cans labelled sealant for MDF but I have been told this is no good for the corners that have been cut and sanded, did you have any issues with these parts of the items you were sealing?


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## WouldBe (Mar 19, 2013)

MDF doesn't have a grain like proper wood. The corners / edges should be no different from the rest of the desk. Unless it's been made from plywood instead of MDF?


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## ViolentPanda (Mar 19, 2013)

evildacat said:


> I have obviously seen these cans labelled sealant for MDF but I have been told this is no good for the corners that have been cut and sanded, did you have any issues with these parts of the items you were sealing?


 
I've seen all sorts of "solutions" to the fact that the edges of MDF, like *any* board, are vbulnerable, from trickling cyanoacrylate adhesive (superglue) onto them, to applying multiple coats of varnish, but what has worked for me is rounding the edges over (something you can do with sandpaper or a file so that the edge is no longer "square", and then proceeding as normal with the sealant. I've used this for about 12 metres of much-used book shelving, and I've got the sum total of zero dents, dings or crumbling edges.


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## evildacat (Mar 19, 2013)

ViolentPanda said:


> I've seen all sorts of "solutions" to the fact that the edges of MDF, like *any* board, are vbulnerable, from trickling cyanoacrylate adhesive (superglue) onto them, to applying multiple coats of varnish, but what has worked for me is rounding the edges over (something you can do with sandpaper or a file so that the edge is no longer "square", and then proceeding as normal with the sealant. I've used this for about 12 metres of much-used book shelving, and I've got the sum total of zero dents, dings or crumbling edges.


 
All the corners are rounded, so things I've been told about putting putty on the open edges and sanding down is not necessary then before applying the sealant? I'm only wanting to protect the desk from say a drink being spilt or similar, as long as it does that and as you say doesn't start crumbling I'll be happy.


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## ViolentPanda (Mar 19, 2013)

evildacat said:


> All the corners are rounded, so things I've been told about putting putty on the open edges and sanding down is not necessary then before applying the sealant? I'm only wanting to protect the desk from say a drink being spilt or similar, as long as it does that and as you say doesn't start crumbling I'll be happy.


 
I knew someone given the putty advice who decided to go one better and use car body filler. The problem with such things as putty and body filler is that they're not inherently adhesive, so unless you give them something to "key" (grip) onto, they'll eventually fall off. 

The reason people say about sanding down is because when you (or the timber yard) cut the MDF, it leaves the "grain" open on the edge (the surface of MDF sheets is kind of "polished" when made, because it's compressed between steel plates and rollers, so isn't open in the same way). Just rub over with a fine grit sandpaper, use a clean lint-free cloth to wipe away any dust from the edge, and then paint the sealant on.The sealant will penetrate the edge and help to stabilise it. Varnishing over that will prevent any worries about spills. Overcoat the sealant with a varnish. That will effectively put a hard non-porous "skin" over anything you apply it to, and as most acrylic varnishes are cross-linking nowadays (in other words the chemicals for a continuous polymer bond) they're as durable as fuck (I finished a bookcase with an acrylic lacquer mixed with acrylic paint that's been knocked about for a good 10 years and still looks good!).


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## evildacat (Mar 19, 2013)

ViolentPanda said:


> I knew someone given the putty advice who decided to go one better and use car body filler. The problem with such things as putty and body filler is that they're not inherently adhesive, so unless you give them something to "key" (grip) onto, they'll eventually fall off.
> 
> The reason people say about sanding down is because when you (or the timber yard) cut the MDF, it leaves the "grain" open on the edge (the surface of MDF sheets is kind of "polished" when made, because it's compressed between steel plates and rollers, so isn't open in the same way). Just rub over with a fine grit sandpaper, use a clean lint-free cloth to wipe away any dust from the edge, and then paint the sealant on.The sealant will penetrate the edge and help to stabilise it. Varnishing over that will prevent any worries about spills. Overcoat the sealant with a varnish. That will effectively put a hard non-porous "skin" over anything you apply it to, and as most acrylic varnishes are cross-linking nowadays (in other words the chemicals for a continuous polymer bond) they're as durable as fuck (I finished a bookcase with an acrylic lacquer mixed with acrylic paint that's been knocked about for a good 10 years and still looks good!).


 
Cheers, will the single coat of sealant do or best with a couple?  will the varnish have to be for MDF or any varnish will be ok?


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## Mrs Magpie (Mar 19, 2013)

Any acrylic varnish


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## ViolentPanda (Mar 19, 2013)

evildacat said:


> Cheers, will the single coat of sealant do or best with a couple? will the varnish have to be for MDF or any varnish will be ok?


 
I'm old-fashioned, so I always put a couple of coats of sealant on anything I'm going to paint or varnish, because with a single coat you occasionally get tiny air-bubbles that don't fill in when drying, so a second coat sorts that out.

Any acrylic varnish will do. I like Chestnut brand, but Rustins is widely available and pretty damn good. A lot of companies that sell wooden products use it.


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## evildacat (Mar 19, 2013)

Thanks for the help.


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