Subject: Re: "Sealing" exposed edges of MDF?

From: patrick anthony <[email-masked]>
Date: Mon, 10 Feb 1997 11:46:38 +1300

John Straffin wrote:
> 
> I'm making a router table to out of some old solid-core door (1-1/2"
> MDF).  Any suggestions on what to do with the exposed wood in the
> center (where the polycarbonate insert will go) so that it doesn't
> chip away, fall apart, or succumb to moisture?
> - John C. Straffin
> [email-masked]

John,

I worked as the Technical/R&D manager for a company that produces MDF
and now I am with a resin manufacturer that produces the glues for the
product. As far as sealing the edges of the panel, there are two main
reasons why you would do this,
1. To minimise any formaldehyde emissions, although most panels are E1
(< 10mgs/100gms ) and if not they should be.
2. To prevent water uptake from the air and accidental wetting. A sealer
will slow down the uptake of moisture from the atmosphere and make the
panel more dimensionally stable.

As for sealers, probably the best type are water based ones, such as an
acrylic undercoat, oil based are not effective with MDF as they get
entrained in the wax that is in the paneland give drying problems etc.
Polyurethane sealers are also quite effective.

I hope this helps you, I have only found this newsgroup and am concerned
a little with the lack of informed knowledge being posted about MDF.

Regards Pat Anthony
	<[email-masked]>

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From: "Thomas E. Koerner" <[email-masked]>
Date: 10 Feb 1997 13:46:10 GMT

John,
I don't believe your door is made with MDF.  MDF would be to heavy for a
door, it is extremely dense.  MDF is used a lot in furniture as a strong,
even consistency base.  Your door probably has a particle or fiber type
filling.  That would flake quite easily because it has a rather loose
consistency.  The openness of the fiber provides a better insulation than
the dense MDF would.  The fiber has many more pockets of air.  I would
suggest discarding the door for several reasons, however for brevity I will
only mention one.  Because of the consistency of the door filling, you may
in time have a problem of it breaking down do to vibrations set up by your
router.  MDF would be an excellent choice, however it is rather expensive. 
Hope that helped some.

-- 
Financial Independence is a choice, not a circumstance.

John Straffin <[email-masked]> wrote in article
<[email-masked]>...
> On Thu, 06 Feb 1997 23:47:39 GMT, [email-masked] (John
> Straffin) wrote:
>

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From: "kenneth.mcwilliam" <[email-masked]>
Date: Mon, 10 Feb 1997 19:02:18 +0000

patrick anthony wrote:
>....

Pat, 

So if you were my friend (mentioned in an earlier post) would you risk
panelling a bathroom (in routed MDF with applied mouldings) even if you
had sealed both sides and edges as you suggest?

P.S. yes I am talking about the 'real' MDF!

Regards Ken McWilliam

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From: Chuck Steger <[email-masked]>
Date: Mon, 10 Feb 1997 17:11:58 -0500

patrick anthony wrote:
> As far as sealing the edges of the panel, there are two main
                                                                         
Pat,                                                                    
   Your second point about preventing water from getting into the MDF   
has me wondering why a water based polyurathane would work. Wouldn't    
that just cause a problem? If not, how many coats do you recommend to   
seal it? Would a regular old polyurathane work?                         
   Thanks.                                                              
-- 
Chuck Steger
Lockheed Martin Federal Systems
Manassas, VA  20110
[email-masked]