I recently built a large MDF project. I painted it semi-gloss white. (Wife’s instructions)
I read about how to seal the fuzzy edges here on this forum. The advice was perfect. I must pass on this wisdom a second time for this MDF product. Hopefully, YOU can provide, another way, to “skin a cat”.
1.) I applied Titebond with water thinned 25%. ( I felt this was toooo thin.)
2.) I applied second coat, same glue with only 10% water.
The result was a rock hard edge that would not soak up the white paint color.
After 35 years as woods teacher and of working solid wood and plywood, this was my first experience with MDF.
Gosh, I was sure surprised at all the dust created during processing this large project and the horiffic smell.
I worry about my students, turned adults, and trying to make a living working with this stuff??? Darned heavy stuff too. Only coarse thread screws work with this stuff too.
MDF excells at veneer substrate only in my opinion. I’m going to opt for high lamination plywood for projects like this job in the future.
What do you guys think about safety of MDF. I bought this stuff at Home Depot. Prolly a representative sample of all of America.
Don
Replies
Don,
Like just about everything else, MDF has its place and it's excellent for some things, not so good for others. I find as I get older I don't make as many rules as I used to about what's the right way to do things.
Regarding the edges - my shop uses drywall compound to seal MDF edges. It's very fast, easy, and does the job.
Milling MDF requires serious dust control, more critically than for working natural wood. If you don't have a real DC system, you're better off not using MDF in the first place. But that's the same as saying that in order to use spray finishes you need real spray equipment.
In general, I find MDF to be a great substrate for veneer or laminates. It's also a great base for painted work of various kinds, and holds up well as long as it's not exposed to moisture, and as long as the edges don't get banged around.
David Ring
http://www.touchwood.co.il/?lang=e&id=1
David,
How do you apply drywall compound to the mdf? It sounds interesting.
Taigert
With a regular garden-variety spatula, about 1" wide.David Ring
http://www.touchwood.co.il/?lang=e&id=1
< Only coarse thread screws work with this stuff too.> I am curious if you were using the screws to join or connect the parts? I normally coat both parts with glue, then just staple it together for that. The fasteners are only to hold it together while the glue dries. The glue is much stronger than any mechanical fastener.
As for self imposed rules, mine is to never use it for something which is not built-in. If I can get it from the shop and connected to the wall without breaking it, I feel OK to use it.
But for furniture or object which get moved around, it is just to easy to break the joints if it gets dropped even just a few inches.
There are other options out there besides what HD offers. You can get an exterior grade, and even a lighter weight grade.
If you want to avoid the time and chore of painting the inside, I like to use white melamine. It is hard to get a paint job that can match it for the price.
As for screws to mount the hardware, I use the euro screws. For any other applications especially if it really needs to hold, or to repair where a screw has stripped out. I fill the hole with thin CA glue, an keep filling as long as it keeps soaking into the fiber around the hole. When this dries, there is a solid plastic plug which needs to be pre-drilled with a pilot hole for the screw to even be driven
MDF is basically just really thick kraft paper (the stuff that ordinary brown paper bags are made of). The dust is a problem, but unless you're routing, it's not too much trouble to keep it under control, as long as you use good dust collection techniques. (I try to avoid routing MDF--there's just no good way to avoid getting dust all over everything.) I use a Festool TS55/CT22E and guide system to cut MDF, and I can cut up a couple of sheets worth of cabinet parts and end up with less than 1/4 cup of uncollected dust that I have to vacuum up.
Glue size and drywall compound both do a good job of sealing the edge. I prefer drywall compound, as it's easier to sand to a smooth finish, but it results in an edge that is prone to chipping (not that MDF is all that strong to begin with, of course). If you just want to seal the edge, and don't care too much about looks, Zinsser 1-2-3 primer works and is as easy as can be.
I wouldn't rely on any kind of ordinary screws that weren't specifically designed for manufactured sheet goods. They'll work, but they'll eventually pull out under repetitively cycled stress. Euro-style and Confirmat screws (large body diameter with thin, sharp threads) work much better. Even so, there's no such thing as a removable MDF screw. After only a couple of in/out cycles, the female threads are toast.
Biscuits work well for glued joints (better and easier than dowels, the traditional method). Dominoes would probably work, too, but I haven't tried.
-Steve
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