# Priming MDF



## finishesbykevyn (Apr 14, 2010)

First off, anywhere I can get away with using a latex primer, I will.
However on most bare woods, I still prefer an oil primer. 
Now seeing as MDF doesn't have tannins of knots, I can see a latex primer as fine.. 
On another note, (which actually stumped me) was a contractor mentioned how an oil primer on MDF would cause a reaction with the chemicals in it. Has anyone heard of this?..


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## Gough (Nov 24, 2010)

finishesbykevyn said:


> First off, anywhere I can get away with using a latex primer, I will.
> However on most bare woods, I still prefer an oil primer.
> Now seeing as MDF doesn't have tannins of knots, I can see a latex primer as fine..
> On another note, (which actually stumped me) was a contractor mentioned how an oil primer on MDF would cause a reaction with the chemicals in it. Has anyone heard of this?..


We've had bad luck with latex primers on MDF. especially on edges/shoulders that have been routed or shaped. Lots of raised grain which didn't sand well. I also worry about the effect of the water, since regular MDF doesn't do that well when it gets wet.

We've had no problems using oil-based enamel undercoaters though. Sands up to leave a surface like glass.


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## Paradigmzz (May 5, 2010)

finishesbykevyn said:


> First off, anywhere I can get away with using a latex primer, I will.
> However on most bare woods, I still prefer an oil primer.
> Now seeing as MDF doesn't have tannins of knots, I can see a latex primer as fine..
> On another note, (which actually stumped me) was a contractor mentioned how an oil primer on MDF would cause a reaction with the chemicals in it. Has anyone heard of this?..


your thinking all chemical, you need to be thinking physical. water raises grain. Oil doesn't. 

As per your last statement, think about it. mdf is wood, boss. So the wood had a chemical reaction with primer?


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## straight_lines (Oct 17, 2007)

There are plenty of good wb primers that work well for mdf. The key to getting good results is sanding before you ever put down any primer. Get to the right grit and you won't have any problems with furring.


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## finishesbykevyn (Apr 14, 2010)

Paradigmzz said:


> your thinking all chemical, you need to be thinking physical. water raises grain. Oil doesn't.
> 
> As per your last statement, think about it. mdf is wood, boss. So the wood had a chemical reaction with primer?


 
Thanks for the feed back on the primers guys. I'm pretty sure i've used both water and oil and never had tooo much issue either. This contractor just got me thinking with that comment...
I don't really see MDF as a wood anymore, anyhow. It's more like sawdust and glue and chemicals. (Directed at Paradigmzz). So you kinda gotta think chemically..right??


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## Paradigmzz (May 5, 2010)

finishesbykevyn said:


> Thanks for the feed back on the primers guys. I'm pretty sure i've used both water and oil and never had tooo much issue either. This contractor just got me thinking with that comment...
> I don't really see MDF as a wood anymore, anyhow. It's more like sawdust and glue and chemicals. (Directed at Paradigmzz). So you kinda gotta think chemically..right??


glue is inert. The only "chemical" reaction is a bonding reaction. And that isn't chemical, it's mechanical. nice try though. As my momma always says: K.I.S.S.


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## Damon T (Nov 22, 2008)

Paradigmzz said:


> glue is inert. The only "chemical" reaction is a bonding reaction. And that isn't chemical, it's mechanical. nice try though. As my momma always says: K.I.S.S.


My understanding is sanding to promote adhesion is mechanical bonding, whereas the resins etc in a primer which enable it to adhere, especially in the case of Stix, 123 etc is chemical bonding.


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## Paradigmzz (May 5, 2010)

Lacquer is a example of a chemical bond. Successive coats remelt previous coats and the coatings interweave. If previous layer or substrate does not melt and interweave chemical structures with the new coating, it is a mechanical bond. glue is not a chemical reaction, even though the bond is solid. This is another reason why deglossing a surface prior to paint is important. Creating a profile allows for a solid mechanical bond.


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## Gough (Nov 24, 2010)

Paradigmzz said:


> Lacquer is a example of a chemical bond. Successive coats remelt previous coats and the coatings interweave. If previous layer or substrate does not melt and interweave chemical structures with the new coating, it is a mechanical bond. glue is not a chemical reaction, even though the bond is solid. This is another reason why deglossing a surface prior to paint is important. Creating a profile allows for a solid mechanical bond.


It's my understanding that there are chemical bonds that don't necessarily involve dissolving previous coats in the way that lacquer and shellac do. For example, I think there are chemical reactions between coats of alkyds if the earlier coat is not completely cured, i.e. within a few days. 

Solvent-based polyurethanes are often used as an example of a material that relies almost totally on mechanical bonds. Even with them, the TDS on some products allow recoating without sanding if it's done within a narrow time window.


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## DanielMDollaPainting (Feb 24, 2011)

I have read talk of priming mdf with oil to prevent latex finish from soaking in and a more uniform finish. That makes sense and would be great but three coats?. I can see priming clear wood with oil or latex, but mdf? Mdf is already primed. The first coat drags like crazy and is slow but whatever. I don't even see a reason to sand because it's nice and smooth. It doesnt have the imperfections like regular wood. Raised grain of real wood always has to be sanded after priming. I caulk up MDF and put on two coats of Superpaint semi and it looks great. Nobody wants to pay for three coats of anything around here let only GC's.


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## Gough (Nov 24, 2010)

DanielMDollaPainting said:


> I have read talk of priming mdf with oil to prevent latex finish from soaking in and a more uniform finish. That makes sense and would be great but three coats?. I can see priming clear wood with oil or latex, but mdf? Mdf is already primed. The first coat drags like crazy and is slow but whatever. I don't even see a reason to sand because it's nice and smooth. It doesnt have the imperfections like regular wood. Raised grain of real wood always has to be sanded after priming. I caulk up MDF and put on two coats of Superpaint semi and it looks great. Nobody wants to pay for three coats of anything around here let only GC's.


When you say, "MDF is already primed", I assume you're referring to pre-primed MDF trim. I was under the impression that the OP was talking about raw MDF, which we see in wainscot, panelling, casegoods, doors, etc


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## finishesbykevyn (Apr 14, 2010)

Gough said:


> When you say, "MDF is already primed", I assume you're referring to pre-primed MDF trim. I was under the impression that the OP was talking about raw MDF, which we see in wainscot, panelling, casegoods, doors, etc


 Yes, I was talking about raw mdf. I am very familiar with the way that different paints dry. Oxidization. polymerizing, solvent evaporation (laquer). I'm wasn't interested in whether or not it was going to stick or not. I was curious as whether or not the VOC's or solvents in some oil primers (which are plentiful) would react to some of the chemicals in the MDF. (I don't know the exact chemical breakdown of MDF) I pretty much new they would't, however I thought I would through it out there and see what other people thought about it.  Thanks for the input fellas. Keepem comin!


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## Toolnut (Nov 23, 2012)

Have always been taught "unless it comes pre-primed use oil on MDF"


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## propainterJ (Jan 31, 2011)

White Lacquer Undercoater dries so much faster then anything else,it;s impossible for me to fathom using anything else.

You can put 3 coats on in an hour,sand it 2 hours later


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## cdaniels (Oct 20, 2012)

I have painted a lot of cabinets made of MDF and have used both latex and oil primers.For me, the latex always made the edges a little rougher so I only use an enamel undercoater now.


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## finishesbykevyn (Apr 14, 2010)

propainterJ said:


> White Lacquer Undercoater dries so much faster then anything else,it;s impossible for me to fathom using anything else.
> 
> You can put 3 coats on in an hour,sand it 2 hours later


Your obviously spraying that on. Are you then top coating with laquer too? On residential job's I really try to stay away from laquers. Way too smelly. I also hate running that stuff through my sprayer. The cleanup is a headache. Literally.:blink:


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## Paradigmzz (May 5, 2010)

all new construction trim should be sprayed out. 


lacquer undercoater is another type of solvent based primer, doubt the intention is to lacquer top coat.


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## straight_lines (Oct 17, 2007)

Lacquer undercoater also comes in wb varieties. It is a very good choice for new wood, and can be sanded very shortly after application.


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## propainterJ (Jan 31, 2011)

YEah it's sprayed on.

Yea it stinks,and I use Lacquers and Lac Undercoats in residential all the time,everytime I need them in fact.

Know what I tell the Customer?

"You want the best right?Well this is it,so sorry about the smell,you may want to go to the movies,or spend the night in another part of the house"

And do you know what they say in return?

"OK""Thanks for the warning"

And no,I don't use Lacquer Paints just cause I primed with LU,I use whatever I want,Acrylic usually.

And cleaning up a rig with lacquer thinner is not that big of a deal,besides the solvent disposal.

But theres nothing that can touch the finish you get from properly primed wood with LU,nothing dries as fast,nothing sands as good,nothing fills the routered edges as well,its what theyd use in a cabinet shop for painted stuff,unless they go with a Conversion Varnish


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## finishesbykevyn (Apr 14, 2010)

propainterJ said:


> YEah it's sprayed on.
> 
> Yea it stinks,and I use Lacquers and Lac Undercoats in residential all the time,everytime I need them in fact.
> 
> ...


 
Ha. That's hardcore. We used to spray out trim in highrises back in the 90's with laquer. You'd get anyone within 2 stories of you high as a kite.
i honestly didn't think many people used laquer anymore. But hey, If ya know it works, don't fix it right!


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## cdaniels (Oct 20, 2012)

I got a call yesterday about fixing some cabinet doors made of MDF built back in the 90's..... edges were rough as a corncob


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## TERRY365PAINTER (Jul 26, 2009)

Use stix and be done with it . There is no way I would spray lacquer in a residential setting . 
I love the results of lacquer under coater , but really hard to sell here in green conscious Austin tx . Stix levels nice and sands really great .


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## HJ61 (Nov 14, 2011)

TERRY365PAINTER said:


> Use stix and be done with it . There is no way I would spray lacquer in a residential setting .
> I love the results of lacquer under coater , but really hard to sell here in green conscious Austin tx . Stix levels nice and sands really great .


What spray rig are you using? I did 8000 lin' of trim last year with Stix and it seemed to plug up my graco 490 pretty good. Still functioned but did not push enough product until a really good cleaning with Laquer thinner. It levels like crazy for an acrylic product though, even when rolled on cabinets.


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## Rcon (Nov 19, 2009)

finishesbykevyn said:


> First off, anywhere I can get away with using a latex primer, I will.
> However on most bare woods, I still prefer an oil primer.
> Now seeing as MDF doesn't have tannins of knots, I can see a latex primer as fine..
> On another note, (which actually stumped me) was a contractor mentioned how an oil primer on MDF would cause a reaction with the chemicals in it. Has anyone heard of this?..


I wouldn't use latex or oil on MDF. 

Oil stinks and dries slowly - latex swells the mdf and is difficult to sand. I've seen oil swell mdf as well and leave a nasty mess. 

What's your application method? If you're brushing or rolling you're kinda limited.


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## cdaniels (Oct 20, 2012)

Rcon said:


> I wouldn't use latex or oil on MDF.
> 
> Oil stinks and dries slowly - latex swells the mdf and is difficult to sand. I've seen oil swell mdf as well and leave a nasty mess.
> 
> What's your application method? If you're brushing or rolling you're kinda limited.


Well....what do you use? Lacquer I guess?


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## Rcon (Nov 19, 2009)

cdaniels said:


> Well....what do you use? Lacquer I guess?


Not lacquer but a WB primer undercoater. My goto would be MLC but most manufacturers (chemcraft, general finishes, target, fuhr etc) would have a similar product. Have to spray it though.


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## Xmark (Apr 15, 2012)

Rcon said:


> Not lacquer but a WB primer undercoater. My goto would be MLC but most manufacturers (chemcraft, general finishes, target, fuhr etc) would have a similar product. Have to spray it though.


Do you trust these wb undercoaters to stick to old poly and nitrocellulose lacquer finishes? what do you use for old cabinets?


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## Rcon (Nov 19, 2009)

Xmark said:


> Do you trust these wb undercoaters to stick to old poly and nitrocellulose lacquer finishes? what do you use for old cabinets?


When I did cabinet redo's i'd only use the undercoaters - never alkyd or acrylic primers. They stick better, dry faster and sand easier. They work better on raw wood of course, but for old cabs they still work better than the alternatives.


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## Custom Brush Co. (Jan 26, 2011)

Xmark said:


> Do you trust these wb undercoaters to stick to old poly and nitrocellulose lacquer finishes? what do you use for old cabinets?


Another reason I turn to PPG Breakthrough... All you have to do is whipe down with lacquer thinner, then hand or machine sand to an even buff sand. If some goes to bare wood, no problem... You just need a perfectly smoothed edge. After removing dust with vac then damp micro-fiber cloth, then simply apply 2-3 coats of the PPG Breakthrough. It can be brushed, rolled, sprayed and it sands really good between coats using a 320 grit sand pad. 

The bond is amazing!

Probably not the easiest product to work with so practice at home! It dries so fast though... However it's self priming, therefore it makes you money when you are good at applying it.


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## Xmark (Apr 15, 2012)

The coating has to be a tough enamel when used for cabinets.i doubt that ppg breakthrough is as hard as a wb lacquer.that said, i'll try it out on some doors and other trim.i'm a big fan of the pitt manor hall for walls and the pitt kitchen and bath semi-gloss for trim & doors.


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## Xmark (Apr 15, 2012)

Custom Brush Co. said:


> Another reason I turn to PPG Breakthrough... All you have to do is whipe down with lacquer thinner, then hand or machine sand to an even buff sand. If some goes to bare wood, no problem... You just need a perfectly smoothed edge. After removing dust with vac then damp micro-fiber cloth, then simply apply 2-3 coats of the PPG Breakthrough. It can be brushed, rolled, sprayed and it sands really good between coats a 320 grit sand pad.
> 
> The bond is amazing!
> 
> Probably not the easiest product to work with so practice at home! It dries so fast though... However it's self priming, therefore it makes you money when you are good at applying it.


here's a differing opinion from Damon T on 07-31-2011, 01:29 PM

Re: Any Updates On PPG Break Through?


"I wish I would have read your other post more carefully, I hadn't realized Easy Sand was part of the problem! It was a big PITA for us too, way too much cleanup after sand, and too porous. The PPG break through was a huge hassle too! The overspray created tons of dryfall which blew around and made a mess. Never again for either of them! I tested the PPG on a couple doors and trim first, and looked ok, but on a larger scale it was too messy. 
Another expensive learning experience I suppose!"


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## mudbone (Dec 26, 2011)

Rcon said:


> When I did cabinet redo's i'd only use the undercoaters - never alkyd or acrylic primers. They stick better, dry faster and sand easier. They work better on raw wood of course, but for old cabs they still work better than the alternatives.


 Are you joking?:blink::whistling2:


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## Rcon (Nov 19, 2009)

mudbone said:


> Are you joking?:blink::whistling2:


No i'm not.


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## Custom Brush Co. (Jan 26, 2011)

Xmark said:


> here's a differing opinion from Damon T on 07-31-2011, 01:29 PM
> 
> Re: Any Updates On PPG Break Through?
> 
> ...


Interesting!! I've used it at least 10 times for cabinets & trim. Brushed, rolled & sprayed. It isn't good to spray on anything you want to keep as with probably all enamels... I use 4x8 sheets of cardboard on the floor & zip walls with .7 mil plastic.


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## Custom Brush Co. (Jan 26, 2011)

Xmark said:


> The coating has to be a tough enamel when used for cabinets.i doubt that ppg breakthrough is as hard as a wb lacquer.that said, i'll try it out on some doors and other trim.i'm a big fan of the pitt manor hall for walls and the pitt kitchen and bath semi-gloss for trim & doors.


You'd be very surprised at how hard the finish is. So hard I shy away from priming cause it's a better primer on it's own. I'd be curious what you think with some tests.


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## Damon T (Nov 22, 2008)

Xmark said:


> here's a differing opinion from Damon T on 07-31-2011, 01:29 PM
> 
> Re: Any Updates On PPG Break Through?
> 
> ...


I've since used it with success. I think part of our initial problem was high temps inside and the guys may have been turning up the pump too much and over-atomizing it. I am still interested in using it again. I am tending to lean more towards Insl-x cabinet coat because it has a longer recoat time. Similar adhesion with maybe a better chance at leveling out. I did shoot 49 exterior condo doors in Breakthrough satin black last summer, and once I figured out how to deal with the direct sun (blocked with tarps etc) it came out amazing. Was out there today doing an interior and had to admire my work ;-)
Custom Brush uses it a lot and I think once you get the learning curve down its a very viable finish.


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## TERRY365PAINTER (Jul 26, 2009)

So with breakthrough in general , lets say cabinets in general repaint . Breakthrough would work pretty good with doing doors both sides in a day . How is the finish compared to advance ?
Also would it be advisable to add extender to it in warmer temps ? 
Just wondering been wanting to try it for awhile now .


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## Damon T (Nov 22, 2008)

TERRY365PAINTER said:


> So with breakthrough in general , lets say cabinets in general repaint . Breakthrough would work pretty good with doing doors both sides in a day . How is the finish compared to advance ?
> Also would it be advisable to add extender to it in warmer temps ?
> Just wondering been wanting to try it for awhile now .


The ppg tech dept said not to thin it with extender, even though ppg sells its own extender. They said only thin it with water. It develops blocking resistance quickly, more so than Advance, which can stay sticky longer. I recently did some cabs and shelves with advance, and several days later the client put books on the shelves, and the heavier ones started to stick to the shelves. The TDS for breakthrough says you can drive a forklift over it the next day. 

I typically try to shoot my cab doors hanging so I can do both sides at once, so I don't know about how quickly you can flip if shooting flat. I think Custom shoots them flat, so maybe he can chime in here. 

The satin finish is similar sheen to advance satin, maybe a little bit lower. Definitely a nice sheen IMO. I haven't used their gloss breakthrough yet, though I think it's sheen rating is similar to the advance semi gloss. The advance gloss is one of the highest rated gloss finishes I have found. Something like 85 degrees or so if I remember right.


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## Custom Brush Co. (Jan 26, 2011)

Damon T said:


> The ppg tech dept said not to thin it with extender, even though ppg sells its own extender. They said only thin it with water. It develops blocking resistance quickly, more so than Advance, which can stay sticky longer. I recently did some cabs and shelves with advance, and several days later the client put books on the shelves, and the heavier ones started to stick to the shelves. The TDS for breakthrough says you can drive a forklift over it the next day.
> 
> I typically try to shoot my cab doors hanging so I can do both sides at once, so I don't know about how quickly you can flip if shooting flat. I think Custom shoots them flat, so maybe he can chime in here.


I would trust weight after 48 hrs without marks being created by constant weight. Since I spray & dry them flat I have experienced faint marks in my work worth touching up. The HO had a hard time seeing them.

However, I'd advise waiting a week before stalking a book shelf!

BTW, thanks for the tip on only using water vs extender! My first instinct was water only, but then I second guessed myself & purchased extender. Good thing I didn't use it...


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## mtnbkr3 (Jan 20, 2013)

Lacquer and oil will seal the mdf much better than any latex. For me it comes down to it's worth it to spray that crap. If you are getting paid enough to do a premium job use the Oil or Lacquer. If not then use a quality latex sealing primer.


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## finishesbykevyn (Apr 14, 2010)

After this long winded thread, I decided to use the stix hybrid primer. Sprayed and back rolled it with a wizz roller. Amazing stuff. Buffed it all down with a sponge and sprayed 2 more coats of dulux latex semi-gloss. No problems at all. However i would normally use a higher quality top coat, but the GC bought all the paint..will post some pics.


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## capepainter (Mar 9, 2012)

A contractor we work for uses tons of mdf and the only primer we,ve ever and only use is bin a minium of 2 coats sanding in between. Never had a problem builtins cabinets ect


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## JRSL Interiors (Feb 15, 2013)

I think it is perfectly good to use a water based primer so long as its quick drying. This will minimise the Mdf swelling. But oil based primers are always give a better finish - Mdf included!


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## Xmark (Apr 15, 2012)

a good bonding/sealing acrylic primer is OK. you might want to seal the ends and raw parts with coverstain or Bin.


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