Replies

1. 
   Shep | Apr 05, 2004 02:43am | #1

     The ultra light MDF doesn't crater like the regular stuff, so you just fill the nail holes and paint.  As a trim carpenter,I don't do much painting, so I can't help you there. A good paint store should be able to recommend something.

1. 
   dbeatty | Apr 05, 2004 03:36am | #2

   thanks for responding. unfortunately i am already working with the ultra heavy variety.

   dbeatty

2. 
   RW | Apr 05, 2004 04:17am | #3

   If the search function was worth a hoot, you'd have your answer. Nice sharp chisel or a flat razor will lick the high points off. For routed edges, the primary thing is to seal it up. People use all manner of means to get to that end. I like drywall conditioner to seal it, and I make a slurry out of Crawfords spackle to fill tiny voids. Some use oil paint, thinned down carpenters glue, . . . it might have been Blodgetts article that talked about using paste wood filler. That ought to work. At any rate, whatever you use, let it dry before subsequent coats. If you keep pumping it in, that mdf could suck in a whole quart of paint, and you could end up with edges swelled and stuck that way.

   "If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man." - Mark Twain

1. 
   dbeatty | Apr 05, 2004 05:41am | #4

   thanks for the ideas. this is the first time i have used the internet for advice. i appreciate the help. i really want something i can brush on because i have a whole house worth of routered MDF casings, etc.

1. 
   RW | Apr 05, 2004 07:05am | #5

   Well it's worth a shot. I can elaborate on my methods of madness. The cut edges, I like the DW conditioner because it's made to suck down fuzzies on a wall and stick them down. You don't really get much fuzz on MDF, but a little. So brush or spray that on. Make sure the can is stirred up real well or you'll leave all the goodies on the bottom of the can. It dries in under an hour. Now it's at least sealed up a little. You can do it a second time if step 2 seems to get sucked dry in nothing flat. Step 2, I love crawfords free spackle. Super smooth. So put some of that in a mix cup and stir it up with water until it's brushable. Not real wet, but a good slurry. Brush that on the edge good, not real thick. You should be able to avoid most slops, but you can wipe off spills with a paper towel.

   I guess the point there is get it worked in, but try not to give yourself too much work sanding when it dries. For a routed contour, you can either use soft sanding blocks (go gentle) or abrasive pads. Sometimes called lacquer pads - looks like scotch brite, but finer. Once you're smooth again, now prime it.

   My "sucking up a quart" comment- I made a worktable with a 2 layer MDF top. I wanted it to be fairly abuse resistant. So I thinks to myself, with the way this stuff drinks, I'll bet . . . and a half gallon of poly later it quit drinking. Took awhile to dry, but that top doesn't have a ding in it, and it's, maybe 8 years later. Just saturated the whole thing. Real easy to clean too, since there's no pores and no gouges."If you pick up a starving dog and make him prosperous, he will not bite you. This is the principal difference between a dog and a man." - Mark Twain

3. 
   ripmeister | Apr 06, 2004 03:47pm | #6

   I've worked with MDF quite a bit for painted cabinetry and custom modings.  If you have sharp bits it should machine quite nicely with little clean-up necessary.  When painting I prime with BIN or some other sort of alcohol based primer.  This dries rapidly, seals and doesn't risk swelling the material, especially on the ends as a water based primer would do.

1. 
   jpainter | Apr 06, 2004 04:26pm | #7

   I've used MDF extensively for trim, paneled walls, etc.  I use Benjamin Moore's Fresh Start primer both to create a good bond on the factory surfaces and to seal in the routed profiles.  After it dries, you may want to hit the routed edges with some 220 sand paper to smooth out the surface.  Worn tooling creates more fuzzies.  I follow the primer with two coats of latex (also Ben Moore, though it hardly matters) and the routed edges blend nicely with the factory surfaces.

   J Painter

4. 
   bill_1010 | Apr 06, 2004 04:42pm | #8

   Seal with a glue size (five parts water one part glue, typeII) or shellac based primer.  This will solve your fuzz problem.  Youll still need to prime if you use glue size but not the shellac based primer.  

   sharp chisel or sandpaper to deal with mushrooming.  As far as putty is concerned, i prefer bondo.   Bondo is easy to use, has a slight tint so you can see where to sand.  Its durable and it sets up faster (hour or so) then many oil based putties.

   Consider using something like 2p10 adhesive for your miter joints to save on nailing the miters, its a stronger bond and requires less nail hole repairs.

   I prefer oil based paint on trim, however its being phased out of production,  consider an acrylic enamel if you opt out of oil based paints.  IMO if you cant spray use oil to brush.  It levels out so much better due to the long open time.