Replies

1. 
   Sancho | Apr 04, 2005 09:00pm | #1

   Is there or was there any exposure to moisture prior to painting? 

   Buck Construction  View Image

      Artistry in Carpentry

           Pgh, PA

2. 
   woodguy99 | Apr 04, 2005 09:13pm | #2

   Ryan, the only thing I've found to make nail holes disappear in mdf is Bondo.  Sand it with a power sander, don't worry about the primer that's already on it, just re-prime with oil based primer.  Usually takes two coats to look good again.  Bondo also helps with those fragile outside corners.  Between the hassle to finish and the superfine dust, I never look forward to days spent with mdf (which includes about half of the past two weeks).

    

   Mike

1. 
   RyanBrant | Apr 05, 2005 05:28am | #4

   Mike,

   My in-laws are probably the most forgiving "clients" one could have.  So these blemishes are really only bothering me.

   1.  But your suggesting puttying the nail holes with Bondo, sand, reprime, then two coats of paint?  Y/N

   And you put Bondo in the tiny gaps in the outside miters - instead of caulk?  And then for my inate curiousity, why is Bondo better than caulk on the miters?

   Thanks.

1. 
   woodguy99 | Apr 06, 2005 01:26am | #11

    

   1.  But your suggesting puttying the nail holes with Bondo, sand, reprime, then two coats of paint?  Y/N

   Almost--putty nail holes w/ Bondo, power sand, prime with oil-based primer (doesn't raise the "grain"), touch up holes/mistakes with Bondo, sand, prime with oil-based primer, then 2 or 3 coats of finish.  It's a lot of steps, but that's what it takes for first-rate work.  

   And you put Bondo in the tiny gaps in the outside miters - instead of caulk?  And then for my inate curiousity, why is Bondo better than caulk on the miters?

   I hate caulking.  It's soft, it shrinks and moves over time.  If you have an outside miter that didn't quite close up, and you caulk it, soon you will see the whole story telegraphed through the paint.  If you use Bondo, the joint has a much better chance at staying invisible, provided you also glued the joint.

   The poster who suggested that a 15ga gun is too big is right on.  I install a lot of 1/2" mdf beadboard, and use an 18ga gun to minimize the size of the holes.  For other stuff, either a 16ga Paslode or 15ga hosed gun.

    

   Mike

    

    

3. 
   DougU | Apr 05, 2005 05:25am | #3

   Ryan

   You have to fill and sand the nail holes on MDF. The nailgun will mushroom the MDF, you'll never hide it with just  paint. 

   Doug

1. 
   RyanBrant | Apr 05, 2005 05:32am | #5

   Thanks Doug.

   Do you personally bother with priming the nail hole after sanding?  And what do fill with?  The other poster, Mike, uses Bondo.

1. 
   DougU | Apr 05, 2005 06:35am | #6

   Bondo's fine, you can use a lot of different things, as long as it doesn't shrink. I see painters use a red product, strait from the tube, no mixing though, I think its similar to bondo. Sorry dont know what its called. Looks like it works great.

   Yes definitely re-prime, if not you'll see it.

   Doug

1. 
   Mitremike | Apr 05, 2005 07:39am | #8

   It is a glazing compound used in auto world--use for pinholes and such great for nail holes dries to fast for much else--find it at auto stores." I reject your reality and substitute my own"
   Adam Savage---MythbustersSorry Doug this was for Ryan----oppps

   Edited 4/5/2005 12:40 am ET by mitremike

1. 
   DougU | Apr 05, 2005 01:42pm | #9

   Thanks Mike

   I thought I heard that it was used in auto body business, wasn't sure. I know the painters like it because it dries fast.

   Doug

4. 
   PhillGiles | Apr 05, 2005 07:24am | #7

   The gun raises bruises (at least it does for me), and you either have to remove the excess or dimple it down. Dimpling gives you a better chance at feathering in filler (Elmer's, Bondo, Polyfix, ...) but is a poor choice for putty-type fillers. If you can find/grind and rounded over drift-punch, then you're flying, if not, try using a light ball pein hammer (like an 8 or 10 oz) as a punch and strike it with a wood/rubber/brass mallet (do not hit a hammer with a hammer, no matter how good your safety glasses are).

   If you decide to cut off that little lip, use an Exacto (or clone) knife. Experience with the product you pick will tell you if you need to fill proud and sand, or fill flush prior to priming.

   .
   Phill Giles
   The Unionville Woodwright
   Unionville, Ontario
5. 
   Mongo | Apr 05, 2005 03:46pm | #10

   The SN40 is a 15ga gun, correct?

   I shoot MDF with 16 and 18ga nails. Never had a significant problem with volcanoes. Minor problem if I nail too close to the edge of a panel, or once when I discovered I was applying lateral pressure on the gun head when firing.

   For the dimples, shave off the dimple with a chisel then fill the nail holes and sand. I use a generic fast-drying wood filler like Elmers. I don't use soft putty.

   Prime with a good oil-based primer, not a latex. Top coat your choice.

   Never had shadows show with these methods, and I use a lot of MDF.

   Technique? If I have an exposed outside corner that I think might see some wear or abrasion, like a baseobard corner from a vaccum hose, before priming I "paint" the outside corner with titebond. It prevents the MDF from possibly flaking.

6. 
   DML | Apr 06, 2005 03:31am | #12

   Just read through this, and I use exactly the same method as Mike.

   In fact I use another method, leave the MDF in the lumber yard and buy wood. Save a tiny bit on material and spend a fortune on labor making it look right, but I understand you may not have had the option.

1. 
   woodguy99 | Apr 06, 2005 04:00am | #13

   Yeah, I avoid mdf too, except for the beadboard product which is superior to wood, IMO.  Sometimes there isn't an option, though.

    

   Mike