Replies

1. 
   a_Furnitologist | Sep 21, 2006 03:52pm | #1

   Been a while since finishing MDF, but the only time we ever sanded (scuff sanded that is) the flats was when one of the guys pulled stock and scratched the surafce of the mdf. We'd bondo and "scuff sand" an area bigger that the damage...nothing worse that a dimple shot with black lacquer, shown under track lighting.  Of course we'd seal all machined edges and use automotive as our  primer of our choice.

   Got a review here in the Books/video Critique Blog-

   http://blogs.taunton.com/n/blogs/blog.aspx?nav=main&entry=7&webtag=fw-bookreviews

1. 
   ddougb | Sep 21, 2006 11:35pm | #3

   Thank you very much!
   Richard

2. 
   nikkiwood | Sep 21, 2006 04:18pm | #2

   Strictly speaking, it is not necessary, but I always scuff sand the the smooth surfaces. It takes just a minute and will promote paint adhesion.

   Also, if I am using a latex paint, I always double prime, since the first coat will raise the wood grain. I rigorously sand the first primer coat, then apply a second coat of primer (which also gets sanded).

   I assume you know about the need for special treating the cut edges.

   ********************************************************
   "It is what we learn after we think we know it all, that counts."

   John Wooden 1910-

1. 
   jarhead | Sep 28, 2006 02:07pm | #4

   I assume you know about the need for special treating the cut edges.

   By the way what and why is the special treating for the MDF cutting edges if you don't mind me asking. Thanks

                              Semper Fi

1. 
   nikkiwood | Sep 28, 2006 04:05pm | #5

   The edges are more porous, and will absorb more paint than the surface of MDF.Let me know if you need suggestions.********************************************************
   "It is what we learn after we think we know it all, that counts."

   John Wooden 1910-

1. 
   jarhead | Sep 28, 2006 04:33pm | #6

   I am currently building an entertainment center out of MDF, for the first time. I generally use Birch cabinet grade. Was trying to keep costs down and since I was going to paint them why not use MDF? I can't seem to see any reason why I would see the end grain of anything I am going to build on this project but was intriqued about the process on how to accomplish the task properly. Just in case I do the doors out of MDF. So thanks for any tips.

   One thing about MDF I don't like is that is doesn't hold up well around moisture. I have used trim in the past that I thought was MDF and you can get it wet with no ill effect. With this project as I chose the MDF thinking I was getting the same properties of the trim but they are not the same due to the swelling of the MDF when it gets wet. Obviously it is a different material. Had some scap pieces in the truck and after a rain, whew the pieces swelled to at least twice the size! But for my application in the house hope thgis won't be a concern....... Or I have worse problems than the entertainment center.  :-)

                                      semper Fi

1. 
   nikkiwood | Sep 28, 2006 07:55pm | #7

   I don't think moisture is a problem with MDF when it is used for interior projects. However, I do prime everything as a precaution (and to limit any residual off-gassing). I don't really think it is necessary though; I do it because it is easy and I'm obsessive. As far as cut edges are concerned, you can buy fillers made specifically for that purpose (from Lee Valley), but I find a smear of joint compound (with your finger) works just as well. I usually use a latex enamel underbody primer (with alkyd top coats), and I will generally brush on two (or even three) coats of primer on the edges.You can also use edge banding -- the kind with hot melt adhesive. But I prefer 1/8" strips that I mill for that purpose. I will often use joint compound on the carcase, and this kind of edging on the doors, since the edges of MDF can be pretty fragile.********************************************************
   "It is what we learn after we think we know it all, that counts."

   John Wooden 1910-

2. 
   jarhead | Sep 28, 2006 08:12pm | #8

   I see now. Thanks. I am assuming the use of joint compound and the such are mainly for asthetics as opposed to integrity of the product.

                                   Semper Fi

3. 
   nikkiwood | Sep 28, 2006 08:27pm | #9

   If you don't use something for the edges (like joint compound), the edge will be "grainy" and appear slightly rough. So yes, it is a matter of aestheics.********************************************************
   "It is what we learn after we think we know it all, that counts."

   John Wooden 1910-

4. 
   jarhead | Sep 28, 2006 08:34pm | #10

   Again Thanks. Do want it to look good!

                           Semper Fi

5. 
   nikkiwood | Sep 28, 2006 08:35pm | #11

   More on aestheics .........I recently made all the trim -- casings, baseboards, etc -- for a renovated house. The second floor stuff was to be painted, and the client did not want to spend the time treating the edges; he just glopped on a couple coats of latex paint, and the edges looked fine to him. For the bathrooms, however, I insisted on using poplar for the base boards and plinth blocks, since he refused to back prime them. I knew there would be a problem down the line with folks mopping the floor, etc.********************************************************
   "It is what we learn after we think we know it all, that counts."

   John Wooden 1910-

6. 
   SCMedLion | Sep 29, 2006 02:09pm | #12

   I am planning to install a panel system in our dining room based on a New Yankee Workshop episode.  After the comments I've just read here I must ask if the routed edges of the raised panels will require any special treatment prior to painting?  The whole thing will be MDF except for solid wood molding at top and around each raised panel.  I may use solid wood for the baseboard now too if the comments above are true.  Any help?

7. 
   a_Furnitologist | Sep 29, 2006 03:33pm | #13

   Hey SCMed:

       If you are machining the raised panels out of MDF.......yes gluesize the machined edges.

       Just think that anytime you machine and expose any internal MDF struucture, prime it.

       Neil

    

    

    Got a review here in the Books/video Critique Blog-

   http://blogs.taunton.com/n/blogs/blog.aspx?nav=main&entry=7&webtag=fw-bookreviews

8. 
   nikkiwood | Sep 29, 2006 03:59pm | #14

   If it were going into my house, for sure I would treat the edges prior
   to painting.I like using the joint compound (applied with a finger) because it's easy to sand.I would then use a heavy bodied primer (I use Ben Moore Latex Enamel Underbody). Sand it, and if there is still any roughness on the cut edges (the raised panels, especially), I would recoat those areas.I would finish with two coats of an alykyd (I use B.M. Satin Impervo), which will give you a durable, glass smooth surface with no brush marks. For a large area like this, I would apply the paint one section at a time with a 4" roller, and immediately brush it out with a China bristle brush. I prefer white China bristle (rather than black) because the bristles are a little softer.Apologies if you know this already ..........********************************************************
   "It is what we learn after we think we know it all, that counts."

   John Wooden 1910-

9. 
   nikkiwood | Sep 29, 2006 04:07pm | #15

   BTW, I forgot to mention I think using MDF for the baseboards would be fine for a dining room. I would however, back prime them before installation, in the unlikely event there is a spill of some sort down the road. It is not necessary to back prime anything else, though.********************************************************
   "It is what we learn after we think we know it all, that counts."

   John Wooden 1910-

10. 
    SCMedLion | Sep 29, 2006 07:57pm | #16

    Please forgive my ignorance, but when you say "back prime" do you mean priming the unexposed areas that will face the wall and floor?

    The plan is to do this in late October/early November.  I had really become excited about this project, but the finish is really starting to sound fussy.  I have purchased a Freud panel-raising bit in the hopes of producing a nice clean profile, and now I am concerned that after I attempt the glue-sizing or joint compound methods you all have recommended it may come off looking messy or I may go nuts with the longer process.  For the joint compound, can it be thinned and applied with a brush like glue size?

11. 
    nikkiwood | Sep 30, 2006 06:01am | #17

    Yes, "back priming" is just priming all the surfaces that would be covered up once the piece is installed. The process is really not that fussy, but it does take time, but not that much more than a 1st class paint job would normally take. The joint compound is already pretty thin, so I would not water it down so it could be brushed. Using your finger is the fastest way of applying it, but you should take a putty knife to scrape off any gobs or excess (to save sanding time. I would suggest you run off a couple of sample strips when you make the raised panels, and use them to experiment with various fillers to see which is the easiest and looks the best under a coat of paint. I have never myself used the glue size, and you may well find it to be the best technique.If you do use the joint compound, I would prime everything first. Sand it down, clean off the dust, and apply the joint compound. Once dry, sand it, and apply another coat of primer to the treated areas.With the glue size, I would apply it directly to the raw MDF, since I would imagine it would stick better.One thing I can promise: if you take the additional time in the finishing process, you will be rewarded for many years -- every time you look at your work. ********************************************************
    "It is what we learn after we think we know it all, that counts."

    John Wooden 1910-

12. 
    SCMedLion | Oct 01, 2006 02:39am | #18

    Thanks.