I am just finishing up the trimwork in my house. Most of the casing & baseboard is MDF. We ripped some of it to fit places where the full width boards would not fit. When spraying the trim upstairs, my daughter noticed that the sawn edges of the MDF soaked up primer like a sponge. Fortunately we used a solvent based primer, courtesy of the advice given on spraying in last Nov’s issue of FHB (The one w/ the photo of a steel roof job on the cover.). Well, the advice was good – our primed trim looks beautiful, really beautiful. Now for the hook! Just read the April issue on MDF work, and there was a one page blurb on painting MDF. In a nutshell (Pistachio, not, coco), It talks about water based paints being absorbed through sawn edges and causing swelling. Hmmmm! Did the primer we sprayed on it protect us from swelling? Or – should I go back and take the advice from the previous article and use oil based finish coat? At the rate we are working, drying time is NOT a factor, by any stretch.
In the FWIW Dept, we used red auto body putty to clean up small stuff after the primer coat and it works wonders. That was recommended in the first article.
Don
Replies
i've used water based primer on cut MDF, haven't noticed any swelling.
Small sample though
bobl Volo Non Voleo Joe's BT Forum cheat sheet
FWIW, I've painted a lot of MDF trim, and have always used Kilz latex. It takes two coats (especially on milled surfaces) but I've never had a problem, as long as you keep it out of damp environments.
check out most recent edition of Fine Homebuiding. They talk about painting MDF and priming it for finish coat. Good article.
Big Bob
One method is to treat MDF "ends" with thinned down (5 parts water to 1 part glue) Weldbond glue. Check out their website.
http://www.franktross.com/
Phill Giles
The Unionville Woodwright
Unionville, Ontario
I just got finished making some baseboard trim out of 1/2" MDF. The problem that I am having is on the routered edge. I cannot get the edge to finish smooth after sanding then priming and painting with latex. Is there tricks to getting a routered edge smooth with MDF? I am a novice and just getting into woodworking.
Thanks,
Ben
Ben: Check this post from RW. Might be what you're looking for.
http://forums.taunton.com/tp-breaktime/messages?msg=30862.2
Rugby
you can use a glue sizing. basical Titebond or other yellow glue thinned down. Apply the sizing and then let dry. Sand the fuzz off lightly and then prime away.
Shellac can work too, same thing apply let dry and lightly sand the fuzz.
Using both i usually lean towards the glue sizing over shellac. Zinnser seal coat shellac is what id use if youre going the shellac route.
As our friend Ben put up his question as a reply to a post which said the same thing (using thinned glue as a sealer), I think we can assume that's beyond his skills..
Phill Giles
The Unionville Woodwright
Unionville, Ontario
omg i didnt realize this was an old post.... Then i review it and you said the same thing.... heh heh
Well, you had (IMHO) the right answer, but I think Ben was really either asking some other question (e.g. how to get better results with a router), or didn't like the answer we gave.
My best answer for cleaner router cuts is to rough with carbide then use a HSS bit for the final pass (and still use the sealer, of course). How about you ?.
Phill Giles
The Unionville Woodwright
Unionville, Ontario