# Please help! Priming MDF paneling



## megaseven (Apr 8, 2018)

Just joined and first post here..

Scenario: I installed mdf paneling, poplar picture frames and a poplar chair rail - all unprimed. Prior to priming, I lightly sanded with 220 then sprayed a very very light coat of kilz2 primer. The tip I used was a 313. The primer was still just slightly tacky after about 2 days which lead to to research the primer which apparently has something like a 25% failure rate. When i ran my finger nail i could actually peel away the primer to the bare wood. Anticipating worst case scenario, i stripped everything and cleaned with a stripper rinse.

Went to SW, spoke with the rep who recommended their multi-purpose latex primer which has a dry touch time of 30 mins and recoat time of 4 hours. Again, lightly sprayed the first coat using 313 tip. A day later, i have the same problem. The primer is slightly tacky and when i go to sand, it doesn't sand to powder; more like goop. There are also portions where i can scrape the primer off to the bare wood. And, the primer is again just ever so slightly tacky to the touch. This goes for the wood, the mdf and the poplar pieces. 

Oh, and lastly, house temperature is approximately 70 deg f, and Ive been running a dehumidifier nonstop.

Does any body have any idea on what's going on here? At first, I thought it was a bad product. Now after using SW, it appears something else is going on. Thank you for any help


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## WestCoast99 (May 8, 2012)

It sounds like you're having adhesion issues. 

Scenario 1) Your primer has not had enough time to cure, harden up, and bond to the substrate. This happens to me sometimes, where a primer doesn't pass the scratch test for a day or two but then after 4 or 5 days it does.

Scenario 2) The primers you are using might not be good enough for what you are trying to do and aren't bonding well enough chemically. If needed, sand the substrate to etch in a "toothiness" to better promote a "mechanical" bond between substrate and primer. 

Scenario 3) The substrate is uniquely incompatible with the primers you have used thus far. Time to up the ante and use an alkyd oil based primer (coverstain), a shellac primer (real or synthetic, there are various options now), or a specialized water based bonding primer (I recently used Sherwin Williams extreme bond with very impressive results, other options are XIM UMA Bonding Primer Advanced Technologies, or Insl-x Stix Bonding primer). 

If odor is an issue or toxic chemicals can't be used on this job I'd suggest trying one of the water based bonding primers first. They may not pass the scratch test right off the bat but should glue down well after a day or two. Good luck and let us know what happens.


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## Wildbill7145 (Apr 30, 2014)

I've used bullseye 123 on miles and miles of poplar trim and never had any of the issues you've mentioned. You've practically got an optimal painting situation there with 70f and a dehumidifier running. I think it's really really weird that the primer still feels slightly tacky the next day, but then again I've never used the primers you've mentioned.


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## WestCoast99 (May 8, 2012)

Wildbill7145 said:


> I've used bullseye 123 on miles and miles of poplar trim and never had any of the issues you've mentioned. You've practically got an optimal painting situation there with 70f and a dehumidifier running. I think it's really really weird that the primer still feels slightly tacky the next day, but then again I've never used the primers you've mentioned.


I'm pretty much with Wildbill on this. Bullseye 1-2-3 is my go-to waterborne primer all the time. I think it's wonderful and has a sheen to it which helps if you need to build up to a satin or semigloss. It sticks to most surfaces pretty well too after 3 or 4 days. But I've had it bond poorly to several things over the years, and then I step up to a waterborne bonding primers like I suggested in my first comment. 

When all else fails I spray coverstain though. Just get your cartridge mask on and ventilate well. That stuff has taken its toll on me over the years. Customers will never know the effort required to give them a pro, worry free finish. We should all be making $90 an hour for using the toxic stuff!


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## cocomonkeynuts (Apr 14, 2017)

megaseven said:


> Just joined and first post here..
> 
> Scenario: I installed mdf paneling, poplar picture frames and a poplar chair rail - all unprimed. Prior to priming, I lightly sanded with 220 then sprayed a very very light coat of kilz2 primer. The tip I used was a 313. The primer was still just slightly tacky after about 2 days which lead to to research the primer which apparently has something like a 25% failure rate. When i ran my finger nail i could actually peel away the primer to the bare wood. Anticipating worst case scenario, i stripped everything and cleaned with a stripper rinse.
> 
> ...


A 313 tip can throw some serious paint down in a small area very quick, sounds to me it may be over application and thus not curing.


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## Woodco (Nov 19, 2016)

I was gonna say the same thing about the 313. Too much paint in to small an area. Try
a 410 or a 411.


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## MikeCalifornia (Aug 26, 2012)

Yep, way to many mils for proper dry. You probably shot over 10-15 mils is my guess, 4 is the norm.


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## rosespainting (Mar 16, 2014)

needs more cure time... I would recommend coverstain, or similar oil based primer for the mdf panels. Let it dry for 2 or 3 days.

I have had similar issues with mdf panels, where water based primer with a 30 min dry time took 2 days to dry.


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## megaseven (Apr 8, 2018)

*Update*

First off, thank you to everyone who replied.

I stopped into SW today and spoke with their sales manager who claimed he never heard of the problem with the latex product. He called into corporate and spoke with a technician who recommended that, since mdf may give off 'gases' or oils [or something like that] and poplar may have a lot of tannon, that I need to indeed step up the game to an oil based primer. They recommended the Problock oil base.

I'm going to test a piece tonight and let everyone know the results!

Thank you again for all of the help!


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## sayn3ver (Jan 9, 2010)

Poplar is pretty much tannin free. Only randomly have I had tannin bleed from poplar and it was probably a real purple green piece with possibly an extra beefy piece of grain or on the rare chance a knot.

Grain raise and fuzziness however is expected with a water borne on polar and mdf. 

Honestly in the situation describe you would have benefited from a pigmented shellac or and oil based primer as an initial application to lock down the grain, fuzz and the mdf. 

If I had to shoot what you did with a waterborne a quick dry undercoat would have been the go to like SW wall wood or ppg fast dry undercoat.

I like the problock aerosol but never sprayed the problock oil myself. Probably would shoot something like bm217or upon another members recommendation, the SW exterior oil primer. Neither are quick dry. 

Sw quick dry oil is like mud. I don't have much experience spraying oil. But man that stuff shouldn't be brushed on trim work out of the tin.

Poplar and mdf don't like water.


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## PNW Painter (Sep 5, 2013)

It sounds like you applied wayyyy to much product. It’s also possible that sanding up to 220 closed the pores of the wood and prevented the primer from penetrating into the wood. 

When I’m spraying primers on raw wood i’ll start with a very light tack coat followed by a heavy coat about 10 min later. 

If you’re looking for a Waterborne primer I’d recommend SW Premium Wall and Wood or BM Advance primer. 


Sent from my iPhone using Tapatalk


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## finishesbykevyn (Apr 14, 2010)

You didn't leave the can in your truck to freeze overnight did ya?


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## jennifertemple (Oct 30, 2011)

I always use a shellac based primer on all wood, no exceptions. It has never let me down! Dries really quickly and letting it dry over night I paint with no issues. Bin is my go to for wood. No doubt, in my mind, it will work as well for MDF.


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## illusionsgame (Aug 1, 2010)

Sounds like a bad can. It does happen. I'd go for my money back man.


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## MikeCalifornia (Aug 26, 2012)

illusionsgame said:


> Sounds like a bad can. It does happen. I'd go for my money back man.


Says every painter when they messed it up.


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## megaseven (Apr 8, 2018)

*Update!!*

I have no idea what happened here, but here is the end result..

After what felt like 10 years of stripping primer, cleaning, and stripping, I lightly sanded the mdf and poplar trim and prepped for primer.

I sprayed the oil based SW problock product [after serious thinning] with a 313 tip. First coat was super light and i let that dry overnight.. Next day, i threw on a good 2nd coat, cranked the heat up to 75, started up the dehumidifier and walked away. I came back tonight and the primer is rock hard - zero issues.

All i can attribute this to is the mdf and poplar not accepting the latex based primers. For ****s, i bought a small pint on the SW multi purpose primer to "retest" on a scrap piece of mdf and poplar..same result as the previous application. The product just never dried and I was unable to sand at all. 

What a horrible ordeal to go through..hopefully this helps someone out in the future!


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## Ramus8T (Jan 14, 2020)

The future here,

It does indeed help. I’m going to spray my mdf bookshelves with an oil based primer instead of a water based primer. 

Thank you kindly. 


Sent from my iPhone using Tapatalk


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## jennifertemple (Oct 30, 2011)

Ramus8T said:


> The future here,
> 
> It does indeed help. I’m going to spray my mdf bookshelves with an oil based primer instead of a water based primer.
> 
> Thank you kindly.



Good Call, can't go wrong, there!


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## finishesbykevyn (Apr 14, 2010)

I dunno, I sprayed some MDF panels with freshstart latex primer a few weeks back and it worked like a charm. Although I did spray 2 or 3 coats. Dryed and recoated in a couple hours. Hardly raised any wood grain..


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## Derrick (Sep 6, 2021)

finishesbykevyn said:


> I dunno, I sprayed some MDF panels with freshstart latex primer a few weeks back and it worked like a charm. Although I did spray 2 or 3 coats. Dryed and recoated in a couple hours. Hardly raised any wood grain..


The only fresh start primer for wood that I’ve liked is 217


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## finishesbykevyn (Apr 14, 2010)

Derrick said:


> The only fresh start primer for wood that I’ve liked is 217


Ya, the alkyd primer is fantastic if you don't have to spray it..


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## AmericanMasterworks (Oct 3, 2021)

Most jobs I these days do not allow solvent and even if they do I can’t afford the time of oil dry times. I accidentally stumbled across Chemcraft products a couple years ago and it almost all I use on new work. Recent paneling job with two larger rooms went like this.

75-85 degrees. Very low humidity. Graco 395 410 ff tip. 1350 pounds measured at gun.

8:00am show up. Set up protection and air scrubbers. 
9:00 sand, caulk, bondo, vac and tack. 
11:00 spray coat 1st of Chemcraft AquaPrime 3-4 mils
11:15 go to lunch. 
12:00 sand and touch up bondo vac and tack
12:30 spray 2nd primer coat 4 mils 
12:45-1:30 return calls. 
1:30 sand tack and vac. 
2:00 spray 1st coat or Chemcraft AquaSet semi-gloss top coat 4 mils.
2:30-3:30 Calls and business stuff.
3:30 spray 2nd coat. No sanding with the prep and air scrubbers (no sags or mistakes this day) 
Water Clean up and remove protection and gone by 5:00.
Durable. Slightly lower than expected sheen. KCMA certification. Beautiful finish.


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## stelzerpaintinginc. (May 9, 2012)

AmericanMasterworks said:


> Most jobs I these days do not allow solvent and even if they do I can’t afford the time of oil dry times. I accidentally stumbled across Chemcraft products a couple years ago and it almost all I use on new work. Recent paneling job with two larger rooms went like this.
> 
> 75-85 degrees. Very low humidity. Graco 395 410 ff tip. 1350 pounds measured at gun.
> 
> ...


Interesting. I'm curious as to whether you're paraphrasing what was done during each time frame or if you actually listed everything in the exact order you did it. If all the steps you listed are in order, it appears as though you're tacking over fresh caulk and sanding over wood you caulked 2 hrs prior. A few questions regarding your schedule...

-30 minutes to sand, vac & tack 2 large rooms with panels? How many employees?
-Not quite sure how you're tacking off the surface you just caulked? What type of caulk are you using?
-Not quite sure how you're sanding at noon wood you just caulked 2 hours prior?
-2 out of the 3 times you stated, "sand, bondo, vac & tack", but aren't you also sanding your bondo? 
-Is your order "bondo, sand, vac & tack" or is it "sand, bondo, sand the bondo, vac & tack"?
-Maximum Dry Film Thickness of the your total coating system is spec'd @ 4mils, yet your 2 coats of primer @ 7-8mils WFT, 48% solids + 2 coats of finish @ 8mils WFT, 33% solids would put you over 6mils DFT, right?

Not trying to be argumentative. Just trying to get a grasp on your actual finishing schedule. I'm also assuming you're only spot-sanding here and there unless you had a very large crew. Without seeing the paneling in those 2 large rooms, it's hard to understand how else you were able to sand, vacuum & tack in a mere 30 minutes, and one of the times, you even touched-up the bondo within that 30 minute time-frame. 

We used to do a ton of new construction where we had houses lined up side-by-side to paint, and could finish a small 3bed, 2.5 bath 1,200sq.ft. interior wood pack in a day, from filling holes, caulking, masking walls, removing doors, spraying them in the garage, priming & painting base, sills, door frames & a single closet shelf in each room, unmask...all in 1 day, but that was with 6 seasoned guys all working in concert over a much more spread-out area than what you're working with. Very interested to hear more about your methods. Thanks for sharing.


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## AmericanMasterworks (Oct 3, 2021)

Not exact time to the second (ie maybe 45 minutes for protection and 2 1/2 hours for prep) but order is correct This was all new work mostly just nail holes. I use bondo glazing putty because it drys to sanding in 10 minutes (instead of Crawfords) Alex fast dry caulk. Desert air. Just me and an apprentice. Surfprep sanders on Festool dust extractors. Not new construction just new paneling and chair rail. For me, a big difference has been the air scrubbers instead of plain ventilation. Two scrubbers cost me about $1100 and they paid for themselves in saved labor in a couple weeks. my between coat sanding is greatly reduced and my lungs aren’t doing the filtering any more. The primer doesn’t need a scuff sand if recoated in less than 24 hours. It definitely does not always go like that but this particular job really showed the advantage of using fast drying products. Drying time and time between coats is the main reason I left BM Advance. The Chemcraft primer is awesome stuff for bare wood and MDF. Does not really raise the grain (magic?) easily sands to a fine powder in 45 minutes but lays out terrific. The second round of bondo is just the holes I missed or didn’t do well the first round. Super thin coat ready to sand and paint in less than 10 minutes. Hit those spots first with a bit of primer. It flashes off in a few minutes then hit all the panels with second coat. There is almost no way to make jobs like this profitable if your coming back 2-3 times. This stuff is tack free in 10 minutes for primer, 20 minutes for topcoat. It’s almost like lacquer but not brittle.
The only down side is it isn’t good for refinishing. No stain blocking and not really high build so doesn’t work for Golden Oak.


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## AmericanMasterworks (Oct 3, 2021)

stelzerpaintinginc. said:


> Interesting. I'm curious as to whether you're paraphrasing what was done during each time frame or if you actually listed everything in the exact order you did it. If all the steps you listed are in order, it appears as though you're tacking over fresh caulk and sanding over wood you caulked 2 hrs prior. A few questions regarding your schedule...
> 
> -30 minutes to sand, vac & tack 2 large rooms with panels? How many employees?
> -Not quite sure how you're tacking off the surface you just caulked? What type of caulk are you using?
> ...


I think I need to clarify. We didn’t do 2 large paneled rooms. I did the paneled wainscoting and chair rail in 2 large rooms. And yes after caulking only spot sanding was done. Where I made repairs.


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## Woodco (Nov 19, 2016)

stelzerpaintinginc. said:


> Interesting. I'm curious as to whether you're paraphrasing what was done during each time frame or if you actually listed everything in the exact order you did it. If all the steps you listed are in order, it appears as though you're tacking over fresh caulk and sanding over wood you caulked 2 hrs prior. A few questions regarding your schedule...
> 
> -30 minutes to sand, vac & tack 2 large rooms with panels? How many employees?
> -Not quite sure how you're tacking off the surface you just caulked? What type of caulk are you using?
> ...


I used to finish a single story house by myself in two days. However, it was single color, two sheens, so wall masking wasnt necessary. My process was:

Label and pull doors and mask hinges. Put all doors in one room. layed on sides
Caulk sills to window frames 
Putty jambs, spackle base, sills and shelves. 
Caulk everything else. 
Mask windows, showers and wherever else needed, which wasnt much, as this is before tile.
Set up pump.
Prime everything, including tops and door bottoms with the same paint we used on the walls (KM 550 Flat. A good quality flat, BTW) 
Clean pump.
Would usually still have an hour or so left in the day, so Id go find one of our exterior crews and help them finish.

Day two: 
Sand everything I primed with half sponges, doing any caulk/spackle touch ups along the way. 
Get into the trim paint KM 1640 semigloss. Very good quality product. 
Spray out all trim with a 211 tip.
Switch to 413, and spray doors in the middle of chosen room, and lean against the wall by the corner. 
Clean pump. 
Unmask
Get a cut pot with the flat wall paint, and cut it 1:1 with water. 
Grab a big brush, and paint down the sides and top of the jambs, and anywhere else the trim meets the wall, about 6-8" out. This just turns the wall back to flat, and touches up perfect. The ultra thinned paint makes this go really fast. 
Go help an exterior crew for the remaining 2 hours or so. 

It was a damn good production system....


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## stelzerpaintinginc. (May 9, 2012)

Woodco said:


> I used to finish a single story house by myself in two days. However, it was single color, two sheens, so wall masking wasnt necessary. My process was:
> 
> Label and pull doors and mask hinges. Put all doors in one room. layed on sides
> Caulk sills to window frames
> ...



I dug up a post of mine from about 5 years ago. It explains the process we did pretty well. Keep in mind that we had already done all walls & ceilings throughout each home, then returned after trim packs were installed. Walls & ceilings were typically painted one color, (usually some form of taupe), with a flat finish everywhere except kitchens, baths & utility room, which got eggshel. The trim was always done in a stock white, using Sherwin's old B47WJ61 Semi-Gloss Quick-Dry Alkyd. Primer was always a lacquer undercoater made by Rodda. I still follow this process to this day for projects with a similar scope of work. Very efficient way to do trim packs while still yielding great results. Anyways, below is the process I'm referring to, copied & pasted from my post in this old thread


When I used to do NC, I'd have my 5 guys start on the trim pack while I removed all doors & hinges, moved em to garage, connect em with 1x2x8's at a lean towards the wall, 2-3 rows. Pre-primed, so only swiped a sponge on the raw ends, paper knobs, blow em off with AC, set up sprayer, spray 2 coats, and the whole thing usually took about 4 hrs. Most were spec homes about 1,400 sq ft ranchers. Average 10 doors per unit plus 6 bi-folds. 

We had our systems down pat too. 1 wood pack a day, start-to-finish, and not like the crap you see in most NC these days. First, wood-to-wall caulked, then wall paint painted over the caulking, (allows for perfect contrast line BTW with no chance of seeing caulk after). Then, filling holes, 2 flush-fills on windows & casings, 1 on base. Then, quickly sand spackle holes to remove any build and/or residue. Then caulk wood-to-wood, then mask, air & vacuum. No finished floors yet, no cabs, so other than 12" perimeter around woodwork, only other masking was toilets, showers/tubs, a fireplace & windows. Then, pigmented lacquer undercoat prime, mdf & sills primed twice, then sanding primer, air, vac & tack, real quick fine-flaw check, 2 coats oil, unmask, and I'd re-hang doors while crew was unmasking & doing clean-up


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## Derrick (Sep 6, 2021)

finishesbykevyn said:


> Ya, the alkyd primer is fantastic if you don't have to spray it..


Actually, I spray it with a wet to wet coat and machine sand with 320 to an auto body type undercoat. The enamel holdout is great, but will also raise the sheen level.


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## jennifertemple (Oct 30, 2011)

*OP April 2018 *


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## finishesbykevyn (Apr 14, 2010)

Derrick said:


> Actually, I spray it with a wet to wet coat and machine sand with 320 to an auto body type undercoat. The enamel holdout is great, but will also raise the sheen level.


 Spraying oil, gross. How exactly does it "raise the sheen level"?


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## Derrick (Sep 6, 2021)

finishesbykevyn said:


> Spraying oil, gross. How exactly does it "raise the sheen level"?


What’s gross about the “spraying” part exactly? I should’ve been more specific I guess, I know if an oil coat goes over 217, the paint drys slower and possibly doesn’t absorb as much. Not sure on the science, I’ve just seen the results.


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## Woodco (Nov 19, 2016)

It gives the illusion of more sheen due to the lack of stipple. Ive seen smooth lids sprayed with eggshell, and where the backroller missed a spot was quite a bit shinier than the rest.


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## finishesbykevyn (Apr 14, 2010)

Derrick said:


> What’s gross about the “spraying” part exactly? I should’ve been more specific I guess, I know if an oil coat goes over 217, the paint drys slower and possibly doesn’t absorb as much. Not sure on the science, I’ve just seen the results.


 Well mostly, because spraying oil is soo sticky. Not to mention a pain in the hole to clean your rig after. I hardly ever use oil anymore.


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## Roscopecotrain (Dec 23, 2021)

megaseven said:


> Just joined and first post here..
> 
> Scenario: I installed mdf paneling, poplar picture frames and a poplar chair rail - all unprimed. Prior to priming, I lightly sanded with 220 then sprayed a very very light coat of kilz2 primer. The tip I used was a 313. The primer was still just slightly tacky after about 2 days which lead to to research the primer which apparently has something like a 25% failure rate. When i ran my finger nail i could actually peel away the primer to the bare wood. Anticipating worst case scenario, i stripped everything and cleaned with a stripper rinse.
> 
> ...


I know how we all wish we could get away with a light 220 sanding. Maybe sand a bit deeper and use an oil prime which also blows. Are we all going to die from lung n brain defects? Eh so be it gimme one mo'. Hey best of luck I'm going on 21 yrs painting this march and having some brews cuz I'm a bit bummed. Pardon me please.


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