# How to prep raw MDF edges on NC baseboards and casing



## dpeters (Jul 18, 2012)

What do you guys use for priming raw MDF in NC? I dont normally do NC, but have a 2000 sq ft addition to paint that is mostly MDF baseboard and door/window casings. All square edge with unfinished edges everywhere. I would use white lacquer undercoater if i was spraying MDF cabinet doors, but cannot use the lacquer product on this jobsite. How do you seal those edges? A high build primer of some sort? Any help would be appreciated.


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## finishesbykevyn (Apr 14, 2010)

dpeters said:


> What do you guys use for priming raw MDF in NC? I dont normally do NC, but have a 2000 sq ft addition to paint that is mostly MDF baseboard and door/window casings. All square edge with unfinished edges everywhere. I would use white lacquer undercoater if i was spraying MDF cabinet doors, but cannot use the lacquer product on this jobsite. How do you seal those edges? A high build primer of some sort? Any help would be appreciated.


 I've been using the "BIN 123" from Zinzer on everything I can.(latex) That stuff rocks. That end grain is always a battle though. I'm hittin it 2,3,4 times if I have to..Any knots or bleeding wood I'll tag with the shellac first.. Sometimes I'll rub a bit of caulking in there too for some build.


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## dpeters (Jul 18, 2012)

Seriously, only one suggestion? Is this an inappropriate question? Trade secret?


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## BrushJockey (Mar 15, 2009)

Not only one suggestion- but it is wrong.
Bin and 123 are 2 completely different primers. one is a shellac base and the other an acrylic.

I don't do NC and very little MDF, but the ACRYLIC 123, or what i like for new wood - Zin's Primecoat2 ( HD) would be worth checking out.


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## Rcon (Nov 19, 2009)

One of our own members makes a primer for mdf which i've had the opportunity to test out in the shop. Excellent build, sprays beautifully with no thinning required, and will seal the cut mdf edges. You will need a no-fil paper for sanding. 

http://www.primesitall.com/index.html


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## dpeters (Jul 18, 2012)

Rcon said:


> One of our own members makes a primer for mdf which i've had the opportunity to test out in the shop. Excellent build, sprays beautifully with no thinning required, and will seal the cut mdf edges. You will need a no-fil paper for sanding.
> 
> http://www.primesitall.com/index.html


Thanks for the input and the link to the product line. I will definitely try it.


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## DanielMDollaPainting (Feb 24, 2011)

I paint new mdf with two coats of Superpaint finish paint. Any bare wood if it's a lot would get any interior latex primer like Zinseer 123.


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## TheRogueBristle (Mar 19, 2010)

Any problem with ends or edges, hit them first with BIN and then cover everything with your favorite acrylic primer. BIn will definitely seal those edges that seem to just drink up the WB's.


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## straight_lines (Oct 17, 2007)

Sherwin Williams kem-aqua performs ok for what you are doing. Its a WB lacquer. 

Biggest thing is to sand bare mdf profiles correctly before you apply anything. You should be above 400 grit on the last pass.


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## Ultimate (Mar 20, 2011)

CS. It's in the truck already. If it isn't it should be. One coat does the trick.


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## 6126 (May 9, 2010)

Ok, heres how I have done it for years..........Hit the edges with caulk when your doing the prep, prime, sand, paint, turn in an invoice, collect check


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## premierpainter (Apr 17, 2007)

We have filled the routed edges or end grains with spackle. Then prime with an oil like CoverStain, then paint away.


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## ROOMINADAY (Mar 20, 2009)

Bad pic, but I have a whole house of this. We made the headers with MDF, we rushed the chamfer install and will prime installed. WB raises ton of fuzz, use any oil, Zinsser Odorless fills and sand nice. We tried Zinsser One WB on raw MDF upstairs...needs two coats with a scuff in between.









Sent from my GT-I9000M using Paint Talk


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## finishesbykevyn (Apr 14, 2010)

BrushJockey said:


> Not only one suggestion- but it is wrong.
> Bin and 123 are 2 completely different primers. one is a shellac base and the other an acrylic.
> 
> I don't do NC and very little MDF, but the ACRYLIC 123, or what i like for new wood - Zin's Primecoat2 ( HD) would be worth checking out.


Not wrong brush Jockey, just mis-named. I always muck the Zinzer names up. But yes, I'm a fan of the Acrylics as well. 123 is a great product.


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## howe (Apr 19, 2010)

I've found the Smart Prime to work best out of all acrylics but you do still get some raised grain. Typically I will go around with a little shellac based and hit all the open ends on MDF. Also! During the caulking stage I will very neatly rub them with caulk and wipe lightly with a slightly damp rag. I know you could be thinking that will show and I worried when I first tried it. But it works like a champ and typically the end grains are shadowed anyhow. It definitely solves the problem of the MDF's drinking problem. 

On raw applications (unprimed MDF) millwork I have always put in the extra step of shellac based primer to start. I helps also with finding all the pins and sands nicely. But of course suffering some extra brain cells in the process.


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## Lazerline (Mar 26, 2012)

I just rub a little caulking on the edges when I'm caulking them in. Looks good to me.


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## Xmark (Apr 15, 2012)

caulking


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## dpeters (Jul 18, 2012)

Thanks for all the feed back everyone. I wound up doing the smart prime-2 coats with a scuff sand in between. Wasn't overly thrilled with the final product but HO was fine with it considering the cost savings of the MDF instead of poplar on the trim work. Next time (hopefully there wont be one) I will try one of the other suggestions. I mainly finish new cabinets and re-store existing kitchens and bath cabinets so I dont get much chance to work on a system for NC work. Thanks again for all the helpful suggestions.


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## dpeters (Jul 18, 2012)

FatherandSonPainting said:


> CS. It's in the truck already. If it isn't it should be. One coat does the trick.


I would have loved to go with CS. It is usually my "go to' for primers, but I was working on an addition to an existing home and HO was sensitive to odor so was looking for a WB solution.


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## dpeters (Jul 18, 2012)

straight_lines said:


> Sherwin Williams kem-aqua performs ok for what you are doing. Its a WB lacquer.
> 
> Biggest thing is to sand bare mdf profiles correctly before you apply anything. You should be above 400 grit on the last pass.


I use that product all the time and I will be using the pigmented Kem Aqua next week, but I actually never thought of it for that application. So used to putting that on as a cabinet finish that I never gave it a thought. I agree on the sanding first. Critical part of "every" paint job in my book. Any one can apply product to a surface, but the prep-work is where the good and the bad get separated.


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