# Primer for MDF sheets



## Jazz_Painter (Feb 22, 2015)

The GC I'm been working with for quite makes more and more his baseboards, door/window frame and trim from Sheets of MDF that he cuts to the right lenght and width. They say it's less expensive and gives a more modern look.

So far as standard procedure I've been using aqualock (which I use as my standard primer) and top coat with pearl latex as we do often here. If the budget allows it, I like to use advance as a top coat for a harder finish, the customers likes it a lot.

I was wandering if you guys would think of a better primer for sealing the mdf and helping with the top coat. So far my system works, but I'm always trying to improve. Also, the side from the mdf is super porous for obvious reasons.

Regards.


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## Zoomer (Dec 17, 2011)

I would say you're getting in the way that you're approaching these paints and primers. I would also consider smart Prime when deciding on a very good primer for MDF. Make certain that if you are using Advanced to only give it one coat per day to allow for complete curing.


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## Zoomer (Dec 17, 2011)

Voice text typos. I would you say you are spot on in the way....


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## TrueColors (Jul 30, 2010)

I use Aqua lock for mdf as well. Seems to be a good system that works for me.... I always say stick to what you know.


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## futtyos (Aug 11, 2013)

Jazz_Painter said:


> I was wandering if you guys would think of a better primer for sealing the mdf and helping with the top coat. So far my system works, but I'm always trying to improve. Also, the side from the mdf is super porous for obvious reasons.
> 
> Regards.


I read this article by Jack Pauhl some time ago regarding applying Gardz over MDF:

http://www.jackpauhl.com/brushing-mdf-so-good-youll-wet-yourself/

I was unfamiliar with painting over MDF until I did some. It sucked up the paint like a black hole! The next job I ran across MDF at, I decided to try the Gardz. I had to paint white MDF crown molding blood red, so I put 2 coats of Gardz on. It still took me 3 coats of the red to get a uniform finish, but it was a lot easier painting than without the Gardz. 

I do not have enough experience with MDF to tell you if Gardz is better than other products, but you might give it a shot, at least on 10 or 20 feet of trim to see what happens.

futtyos


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## PremierPaintingMa (Nov 30, 2014)

I use BM Enamel Underbody Primer(217) never failed me. Easy sanding, great for sealing the mdf, excellent for top coat finish, specially for Advance.

Dan.


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## Jazz_Painter (Feb 22, 2015)

futtyos said:


> I read this article by Jack Pauhl some time ago regarding applying Gardz over MDF:
> 
> http://www.jackpauhl.com/brushing-mdf-so-good-youll-wet-yourself/
> 
> ...


That's very interesting, thanks for posting it! That being said I'm talking about unprimed mdf sheets that are cut to frames and baseboards dimentions.


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## straight_lines (Oct 17, 2007)

Kem aqua plus surfacer.


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## beaglepower (May 5, 2015)

The water based primers don't cause the mdf to swell up?


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## futtyos (Aug 11, 2013)

*MDF soaking up water?*



Jazz_Painter said:


> That's very interesting, thanks for posting it! That being said I'm talking about unprimed mdf sheets that are cut to frames and baseboards dimentions.


Jazz_Painter, you make an good point about the MDF being unprimed. I have only painted or Gardzed over primed MDF. From what I am reading, it is recommended to prime raw MDF with a non-water based primer so that the fibers do not swell and make sanding an impossibility. That being said, why does primed MDF suck water based primer or paint up like a black hole, but does not seem to swell the MDF? Maybe it does and I just am not seeing it properly?

futtyos


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## lilpaintchic (Jul 9, 2014)

I like oil.


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## lilpaintchic (Jul 9, 2014)

beaglepower said:


> The water based primers don't cause the mdf to swell up?
> 
> 
> Sent from my iPhone using Tapatalk


They do tend to raise the grain higher and be more difficult to sand than oil for about the same price. Imo...


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## chrisn (Jul 15, 2007)

lilpaintchic said:


> I like oil.


I like 10W-40 myself


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## Wildbill7145 (Apr 30, 2014)

lilpaintchic said:


> They do tend to raise the grain higher and be more difficult to sand than oil for about the same price. Imo...


Grain in MDF? Never heard of that. I haven't had to deal with much MDF trim, but when I have I've used my go to primer Bull123 and I've never had a problem.

A few years ago though I did have to paint an entire house of MDF doors that were preprimed. What a nightmare. Sanded the primer, dusted for prep. These things sucked up the first coat in a way I'd never seen before. Paint literally dried to the touch in seconds. Fully loaded brush was empty pretty much as soon as it touched the surface. Second coat went far better, but man you had to be careful on the first.

Never seen anything like it before.


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## lilpaintchic (Jul 9, 2014)

Did I mention I like oil? Mdf absorbs water like a thirsty sponge. You can use 123 or whatever but I get better results from coverstain. Or sometimes (like last week) a bomb can of kilz or 2 does the trick nicely. Brushing new mdf is a nightmare no matter what you're using though.. I just think oil sands out smoother and flows a bit better. To each their own...
And "raising the grain" is the best way I could express the effect of what water based products do to the surface of mdf. Its such a drag. (Pun intended) Especially unprimed. Check it out for yourself some time...


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## futtyos (Aug 11, 2013)

*Fibers, not grain?*



lilpaintchic said:


> Did I mention I like oil? Mdf absorbs water like a thirsty sponge. You can use 123 or whatever but I get better results from coverstain. Or sometimes (like last week) a bomb can of kilz or 2 does the trick nicely. Brushing new mdf is a nightmare no matter what you're using though.. I just think oil sands out smoother and flows a bit better. To each their own...
> And "raising the grain" is the best way I could express the effect of what water based products do to the surface of mdf. Its such a drag. (Pun intended) Especially unprimed. Check it out for yourself some time...


How about saying that water based raises the fibers?

futtyos

P.S. I think I will try Coverstain next time I run into MDF, which I hope does not happen.


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## Wildbill7145 (Apr 30, 2014)

One thing I've always hated about MDF trim is when the carpenters hit it with their 18g nailers and you get the bulge. Never happens with real wood.


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## Jazz_Painter (Feb 22, 2015)

lilpaintchic said:


> I like oil.


Do you find coverstain to do a better job at sealing the edge as well? Cause the edge is so unbelievably porous... that's where I feel the most pain painting, especially when I have to cut them.


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## lilpaintchic (Jul 9, 2014)

Jazz_Painter said:


> Do you find coverstain to do a better job at sealing the edge as well? Cause the edge is so unbelievably porous... that's where I feel the most pain painting, especially when I have to cut them.


Yes. Depending on what's going on, some times I hit it, sand it and hit it again...the "trick" is to build it up enough to get it smooth.


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## cairnstone1 (Sep 11, 2016)

i had a sheet i painted up and just grabbed sw multipurpose. rolled it on thick let it dry and sanded with the 6 inch rotary. topcoat was all surface semi came out looking smooth


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