# Question about laminating MDF ? formica , hardboard



## tryingtokeepmyfingers (Jun 3, 2008)

so here is the deal 

building a table out of 2 pieces of of 3/4 mdf glued together

now the top will be white formica 

now I have read here most people say you need to put formica on the underside to keep the table from warping to seal the mdf from warping... 

so since formica is expensive how would it be using tempered 1/4 hard board glued to the bottom of the table instead of the formica....

I am edge banding the whole thing in 3/4 pine that I am putting on with biscuits to the side of the table 

thanks


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## istracpsboss (Sep 14, 2008)

Sounds fine. You just want the top to have the same humidity exposure to both sides. Even waxing the underside would probably work.

Cheers

Peter


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## tryingtokeepmyfingers (Jun 3, 2008)

istracpsboss said:


> Sounds fine. You just want the top to have the same humidity exposure to both sides. Even waxing the underside would probably work.
> 
> Cheers
> 
> Peter


Thanks peter


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## Ralph Barker (Dec 15, 2008)

The underlying concept is to keep laminations as "matched" sets of material having the same expansion coefficient - like properly-made plywood, a core encased in matching sets of veneers. 

MDF doesn't have a conventional expansion coefficient, but _is_ subject to moisture absorption, which could induce some warping. Tempered hardboard would be subject to the same sort of effect. If you don't want to apply Formica to the bottom surface, I'd suggest sealing it with a couple of coats of shellac, and then wax it if you want. Shellac is an excellent moisture barrier.


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## jschaben (Jun 21, 2009)

I'm wondering if biscuits in the MDF are a good idea. Never tried it but MDF seems a bit sensitive to having the edges messed with.


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## barking spider (Dec 26, 2010)

I used to paint the unseen surfaces of cabinets with leftover latex paint I had around. #1, to get rid of the paint, and #2, to seal the exposed surfaces to protect from humidity. I'm sure it may have brought up some questions if someone ever tore apart the kitchens.


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## pal (Feb 13, 2008)

Ralph has hit the nail on the head with "The underlying concept is to keep laminations as "matched" sets of material having the same expansion coefficient - like properly-made plywood, a core encased in matching sets of veneers. "
.The biscuits in MDF will work just fine ,but they really aren't needed as they are only used for alignment and add little if any strength to the join.

Harold


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## jcr3 (Mar 12, 2011)

I personally have never experienced MDF warping with or without a laminate surface on it, but then again, when ive used "Formica" it has been for kitchen or bathroom countertops, or workshop surfaces, or even cabinets with the doors and cabinet outsides being laminated only. I am sure the previous suggestions of shellac or paint would be fine. Unless your 3/4" pine edgebanding is gonna take alot of abuse, then glue and pin nailing it will be all you need to do.


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## papawd (Jan 5, 2011)

So from what I am hearing is shalacing the best way to cover mdf ?


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## tryingtokeepmyfingers (Jun 3, 2008)

thank you to everyone for all the input it has been very helpful


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## derek willis (Jan 21, 2009)

Has anybody cosidered doing what I did all those years ago with my table, that is, use a piece of kitchen worktop, so stable, no warp, easy to work, and should last for always, mine is now almost 20 years old.


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## derek willis (Jan 21, 2009)

Has anybody considered doing what I did all those years ago with my table, that is, use a piece of kitchen worktop, so stable, no warp, easy to work, and should last for always, mine is now almost 20 years old.

router table.jpg (3.0 KB)


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## LinuxRandal (Mar 11, 2011)

Derek, sounds like what a late friend used to do. He used a sink cutout for his table.


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## Phil P (Jul 25, 2010)

jcr3 said:


> I personally have never experienced MDF warping with or without a laminate surface on it, but then again, when ive used "Formica" it has been for kitchen or bathroom countertops, or workshop surfaces, or even cabinets with the doors and cabinet outsides being laminated only.


Do you live inland, away from the sea or in an area of stable humidity? Or for that matter were the items you made to be installed in air-conditioned environments? If so you'd see little movement. However here in the UK we have a very variable climate and an air MC which zooms up and down regularly - so shop and bar fitters tend to laminate both sides of most pieces to sidestep the issue of warping.

Phil


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## pal (Feb 13, 2008)

Being in a high humidity area I also built my router table out of a bench top off cut. The material is called AQUABAN and is 33mm thick HMR chipboard, one side is already covered with a thin plastic membrane so it was only necessary to laminate one side and the edges.


Harold


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## jcr3 (Mar 12, 2011)

Phil, Now that I think of it all my laminated projects/jobs were in Southern California. and were used in an AC environment. The humidity level in So Cal seems to be pretty stable. But if you go to any Home Depot or Lowes stores and buy (or order) pre-laminated countertops, they are always bare on the bottom. Of course for all I know, they may spray something on the bottom thats looks invisible??

John


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## derek willis (Jan 21, 2009)

Here in the U/K all worktops are covered both sides, although the underside is of very poor grade, therefore they never warp.


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## Phil P (Jul 25, 2010)

jcr3 said:


> But if you go to any Home Depot or Lowes stores and buy (or order) pre-laminated countertops, they are always bare on the bottom. Of course for all I know, they may spray something on the bottom thats looks invisible??


Hi John

As Derek says here in the UK post-formed, laminated kitchen counters (worktops) always seem to have a low-grade backer applied which can look a lot like grey/brown paper, although firms like Egger use a backer in their house colours with a logotype applied and in the house colours. This backer is often in fact a phenolic-impregnated paper which is structurally similar to the top-coating on a sheet of Formica but without the shiny top foil layer. On the rare occasions I've seen pre-manufactured countertop with visible particle board grain it's always had some or other clear sealant applied which made the surface darker than the core. If you didn't do this in our climate the worktop would bow badly within a matter of days

Regards

Phil


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## pal (Feb 13, 2008)

Hi This is the back of the postformed bench tops here in Australia. they are supplied by Laminex with this backing already attached and you only have to put the profile you require on the front lip and then glue the laminate on the face.The first photo shows (in a fashon) how the laminate is wrapped around the front to meet the back seal.

Regards

harold


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## AxlMyk (Jun 13, 2006)

All I did was use a lot of paste wax on the double 3/4" MDF top. All is well after 4 years.


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