# Priming MDF and bare trim



## jadcanno (Feb 3, 2013)

I've recently finished several rooms with extensive MDF wainscoting and coffered ceilings. I decided to use Zinsser "Cover Stain" Oil-based Primer as MDF doesn't seem to agree with MDF edges and the water base version doesn't sand as well. I'm using a 2.5" Purdy Black bristle brush but am having a really hard time getting a decent (smooth) finish without having to go back over the primer, after it has dried, with a light scraper or sand paper. The new oil based primers seem to dry too quickly and, coupled with the dryness of winter, there is limited leveling out. I switched over to SW Pro Block primer in hopes that I would resolve these leveling issues (guys at SW told me it would) but other than a different smelling solvent used, it was an identical product. Can't help but think that I'm missing something as I used to use an oil based primer from Duron (when I lived back east) and always had great results because the paint dried considerably slower. The primers are already thin and wouldn't take penatrol too easily. I'd greatly appreciate any ideas. Thanks


----------



## smakmauz (Feb 17, 2013)

Hey there, I don't know about anyone else but I've never had any luck combatting the problem you have either. MDF is so porous when cut that it will soak up just about anything, 'raising the grain' so to speak. The only thing that I've done if I've had to use the exposed 'end grain' of MDF is to either prime it with an oil or shellac and then sand it and prime again to smooth it out.

If you've had luck with a slower drying oil primer then try the benny moore fresh start line. they have two oils... standard which is an overnight (10-12 hr) or the quick dry which is still 4-6 hours. Ive not ever tried them on MDF but they are definetly not a fast dry like the zinsser. 

Off the exact subject here but, if you ever want a fast dry dry oil primer... see if you can find Z-prime in your area. Its by a company called Zehrung and it is a great product. Way better than zinsser IMHO.


----------



## Damon T (Nov 22, 2008)

I'm guessing you are brushing? Since you mentioned the 2.5". brush. I know dumb question but wanted to be sure. So cover stain may be good for spraying but I would not try to brush it on nice trim, as you've discovered. As mentioned BM makes a great oil enamel underbody. 

Enamel Underbody Primer (217)

Smooth leveling
Flows smoothly for an even finish
Easy to sand
Great paint gloss retention
Ideal for wood trim, doors, cabinets and other surfaces where an ultra-smooth topcoat is desired

If you are brushing this is the Cadillac of enamel under body's. 

JP had a great post on using Zinsser Gardz on mdf prior to painting instead of oil primers. I tried it on a bunch of crown and it worked really nice. It's another option.


----------



## smakmauz (Feb 17, 2013)

Damon, are you talking about using gardz mostly on the cut ends of MDF? I think thats what he's having trouble with.

I haven't ever tried Gardz but it looks kind of interesting. Sounds like maybe its like thinned down elmers glue.... not really a bad thing... that could work nicely for a lot of different things.

Does it really sand out well?


----------



## Damon T (Nov 22, 2008)

Actually it was more for overall priming of the mdf, not just the cut ends. Though it would probably be good for that too. The idea was if you seal the Pre primed mdf with Gardz it will then let the topcoat flow out really nicely as the mdf won't be grabbing at the paint.


----------



## Damon T (Nov 22, 2008)

Also, it flows out so smooth that there's not much sanding. It's like spreading water over the surface. No brush marks to sand , just a quick shot with 220 prior to finish coat.


----------



## smakmauz (Feb 17, 2013)

gotcha. yeah you can't really use pre-primed MDF as is if you want a really smooth finish.


----------



## smakmauz (Feb 17, 2013)

i'm gonna have to try this stuff out...


----------



## jadcanno (Feb 3, 2013)

Thanks so much for the replies, Smakmauz and Damon. I'm going to run out this morning and get some of the Benjamin Moore Primer. I'll relegate the rest of the Sherwin Williams Pro-Block for when it gets a little warmer and I can spray. I'll probably have found the Zehrung product by then (I used to use Z prime all the time, while in the motion picture industry, and loved it. I haven't seen it much in the Northern Midwest, but will keep an eye out for it. Thanks again!


----------



## TrueColors (Jul 30, 2010)

I've had no problems with ben moores Latex primer/enamel undercoat when priming bare MDF. I just painted about 200ft of it with the above primer. Looks good.


----------



## kdpaint (Aug 14, 2010)

Ive done the Gardz thing. It works really well.


----------



## Scotiadawg (Dec 5, 2011)

B.I.N works for me.


----------



## smakmauz (Feb 17, 2013)

Scotiadawg said:


> B.I.N works for me.


B.I.N is the only zinsser product I really like. Pigmented shellac...dries in a snap and seals up anything and sticks to just about anything too. That's my number one problem solver. That would be my first choice in sealing up raw MDF as well. Although I would usually have to coat it then sand it and coat it again to get a factory like finish.


----------



## Scotiadawg (Dec 5, 2011)

smakmauz said:


> B.I.N is the only zinsser product I really like. Pigmented shellac...dries in a snap and seals up anything and sticks to just about anything too. That's my number one problem solver. That would be my first choice in sealing up raw MDF as well. Although I would usually have to coat it then sand it and coat it again to get a factory like finish.


Sands really nice tho:thumbsup: .


----------



## smakmauz (Feb 17, 2013)

Scotiadawg said:


> Sands really nice tho:thumbsup: .


Indeed it does!


----------



## Scotiadawg (Dec 5, 2011)

I just tried a BM primer ( freebie) and was very impressed. AquaLock or something like that it's called - no Im not goin out to the shop to check. Mighta been AquaSeal . Anyway Aqua something or other worked like a charm on that  MDF trim with end "grain" exposed - no returns on this trim. I was very pleased with the way it sealed that crap.:thumbsup:


----------



## kdpaint (Aug 14, 2010)

In the states Aqualock is Insulx brand. BM bought them up a while back. For an inexpensive kinda all purpose primer it is my go to for a lot of jobs.


----------



## HJ61 (Nov 14, 2011)

Scotiadawg said:


> I just tried a BM primer ( freebie) and was very impressed. AquaLock or something like that it's called - no Im not goin out to the shop to check. Mighta been AquaSeal . Anyway Aqua something or other worked like a charm on that  MDF trim with end "grain" exposed - no returns on this trim. I was very pleased with the way it sealed that crap.:thumbsup:


Aqualock is there acrylic primer, and Primelock the alkyd primer.


----------



## jadcanno (Feb 3, 2013)

Just primed the MDF with BM Fresh Start 217. Looks nice and definitely didn't dry as quickly. The "slick" side (uncut) of the MDF does leave brush marks still but not too bad. A light sand and it'll be good to go in the morning. Only negative was that this was easily the most expensive primer that I've ever used. $39 for a gallon! I'm thinking that there must be an Alkyd primer out there that isn't overpriced but I'm afraid that the VOC restrictions have made it easy for companies to gouge us in an effort to deter the use of solvent based products. Oh well. Thanks again for all the responses. I really appreciate it.


----------



## smakmauz (Feb 17, 2013)

Yeah ... Benny Moore definitely ain't cheap. I'm not a huge fan of there stuff because I don't think its as good as what they charge but its kinda hard to find a slow dry oil these days. When you need it, you need it.

Aura is really nice but I'm sure as hell not gonna pay $60 a gal for it unless the customer specifically asks for it.


----------



## Repaintpro (Oct 2, 2012)

smakmauz said:


> B.I.N is the only zinsser product I really like. Pigmented shellac...dries in a snap and seals up anything and sticks to just about anything too. That's my number one problem solver. That would be my first choice in sealing up raw MDF as well. Although I would usually have to coat it then sand it and coat it again to get a factory like finish.



Shellac based is the way to go and Bin seem to have the best of it. The Shellac does not fur the edges like a water based product. I also dont thin any product I am putting on the edges of MDF as it makes the furriness worse.


----------



## Damon T (Nov 22, 2008)

jadcanno said:


> Just primed the MDF with BM Fresh Start 217. Looks nice and definitely didn't dry as quickly. The "slick" side (uncut) of the MDF does leave brush marks still but not too bad. A light sand and it'll be good to go in the morning. Only negative was that this was easily the most expensive primer that I've ever used. $39 for a gallon! I'm thinking that there must be an Alkyd primer out there that isn't overpriced but I'm afraid that the VOC restrictions have made it easy for companies to gouge us in an effort to deter the use of solvent based products. Oh well. Thanks again for all the responses. I really appreciate it.


I think they used to have a contractor grade enamel underbody, super spec something. Maybe they still do. That 217 is nice stuff though. I don't worry about the price of paint for trim paint usually, a gallon of trim paint covers a lot of surface area, surface area that makes me money hopefully!


----------



## propainterJ (Jan 31, 2011)

I use lacquer undercoat and lacquer paint that dries twice as fast as shellac,sands twice as good,and is VOC compliant here in California.

VOC 275 pr gallon


----------

