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Painting MDF and got some brush marks...

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Forum topic by AAANDRRREW posted 06-08-2017 12:34 PM 1000 views 0 times favorited 17 replies Add to Favorites Watch
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AAANDRRREW

210 posts in 1081 days


06-08-2017 12:34 PM

So I have put tons of effort into carefully building a beautiful fireplace surround out of MDF. I sanded it with 120 (RO sander), did a coat of zinnser bullseye primer, sanded again, another coat, sanded again then a coat of hallman lindsays aqua alkyd paint. I have done the process many a time on my oak trim and doors with good results. I use a good Purdy brush, move quickly and lightly backdrag the brush to flatten out the strokes and the paint usually self levels and life is good – not with this so far. I’m not sure if its the extreme smoothness and flatness that the MDF has that doesn’t hide the strokes like the oak doors do or what.

So, at this juncture, I was going to sand it again with 120 and paint again, this time trying a different brush. Could it be that my primer and paint were purchased last september and have sat (sealed) 1/2 full since then? I’m paining in the house and it’s been in the 70’s outside, not real humid and even one day the AC was on…

Also, I have tried a foam roller on other projects, but it leaves a really small but rough texture (almost like a sandpaper feel) – can someone point me to a good roller (that say menards or home depot carries) that wouldn’t leave as much texture? I’d like to get a small one because a fullsize roller won’t fit between the face frame in certain places.

Really pissed and discouraged that after all the effort into making this perfect I have brush strokes like I do. Sanding is more difficult now too because the paint doesn’t sand as nicely as the primer. My wife says it’s fine and she can’t hardly see them unelss she gets close, but she’s just being nice and doesn’t want to piss me off more. It does look fine until you get at the right angle and sun is shining in the window and the marks are clearly visible…


17 replies so far

View GR8HUNTER's profile

GR8HUNTER

3306 posts in 621 days


#1 posted 06-08-2017 01:39 PM

try this method : https://www.youtube.com/watch?v=pZR8WiTYC1Y
GOOD LUCK :<))

-- Tony Reinholds,Pa. REMEMBER TO ALWAYS HAVE FUN

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Nubsnstubs

1249 posts in 1639 days


#2 posted 06-08-2017 02:05 PM

Andrew, if your wife is happy with it, leave it alone. Quit obsessing about something you won’t even notice in 6 months.

Have you watched the Hillbilly video. Heck, he hasn’t even puttied the nail holes and the seam between the face frame and carcass, and he’s proud of his paint job. Otherwise, he wouldn’t have posted his video…...... Jerry (in Tucson)

-- Jerry (in Tucson) www.woodturnerstools.com

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hotbyte

991 posts in 2884 days


#3 posted 06-08-2017 02:28 PM

You could try a little Floetrol to see if it let brush strokes level out better. I used some in an Ace brand waterborne alkyd at it worked well. I wasn’t sure if I should use Floetrol (water based additive) or Penetrol (oil based additive). Since instructions said thin with water, I went with Floetrol.

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AAANDRRREW

210 posts in 1081 days


#4 posted 06-08-2017 02:45 PM

Nubstubs – easier said than done :).... I will notice it in 6 mo and still get pissed haha.

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GR8HUNTER

3306 posts in 621 days


#5 posted 06-08-2017 03:13 PM

we are most critical of our own work ….but HAPPY WIFE HAPPY LIFE :<))

-- Tony Reinholds,Pa. REMEMBER TO ALWAYS HAVE FUN

View rwe2156's profile

rwe2156

2804 posts in 1390 days


#6 posted 06-08-2017 03:51 PM


So I have put tons of effort into carefully building a beautiful fireplace surround out of MDF.
MDF is a PITA in many ways, especially painting. It needs to be sprayed to look good.

That being said, I have brush painted several steel doors with gloss oil paint and they look really good. I suspect the same would apply to MDF. I’ve always thought you aren’t supposed to put oil on top of latex so I don’t know what to tell you about that.

-- Everything is a prototype thats why its one of a kind!!

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AAANDRRREW

210 posts in 1081 days


#7 posted 06-08-2017 04:16 PM

My primer and paint are both water based.

yes, MDF is a pita when it comes to dust and assembly, but I was told it paints up so nice. It is sure nice, flat, square and cheap.

View pintodeluxe's profile

pintodeluxe

5569 posts in 2722 days


#8 posted 06-08-2017 04:19 PM

Spray it. Spraying is the only way to eliminate brush marks.

Especially if you are trying to brush vertical surfaces (as in the mantle is already installed).
If it were laid flat in the shop, you might have a chance of the paint leveling out. But with vertical surfaces it’s not going to happen I’m afraid.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View dday's profile

dday

138 posts in 1338 days


#9 posted 06-08-2017 04:23 PM

“MDF is a PITA in many ways, especially painting. It needs to be sprayed to look good.”
+1 on this

It seems no matter how I prep or seal it, MDF absorbs paint quicker than I want it to and it looks streaky or shows brush strokes.

Spraying, even with a cheap gun from HF, leaves a smooth finish.

View 01ntrain's profile

01ntrain

237 posts in 979 days


#10 posted 06-08-2017 06:16 PM

I always seal it first with an oil-based primer, it will swell with water-based…..then use the waterborne alkyd. But, yes it def is a PITA.

View SignWave's profile

SignWave

440 posts in 2944 days


#11 posted 06-08-2017 06:24 PM

Although it’s water based, I suspect that the enamel paint will sand decently if you wait for it to fully cure. I use the Sherwin Williams version of water-based enamel and it does harden enough to sand, much more so than a regular latex paint. Give it a week or two.

If you cannot get the surface to be horizontal while painting, then I agree that spraying is the way to get a smooth finish.

-- Barry, http://BarrysWorkshop.com/

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AAANDRRREW

210 posts in 1081 days


#12 posted 06-08-2017 07:14 PM

damnit. well, my buddy didn’t tell me it was a PITA to brush or roll. That being said, spraying isn’t an option because its installed already. I’m hoping I can sand it nicely and then maybe use a roller – I can deal with texture before I can stomach brush strokes.

Signwave – so, when I was sanding the primer it left little tiny BB balls, not dust. I figured it was because I was using too fine of paper or it was my vibrating sander instead of the RO sander – if I let it sit longer it will sand better? All the coats had a least 48 hrs to cure.

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Kazooman

940 posts in 1861 days


#13 posted 06-08-2017 07:34 PM

The small foam roller will leave a texture as you said. The problem with that is that you cannot readily get the roller into corners and will have to cut those in with a brush. Texture in the field and smooth at the edges. That really stands out. Try it on some scrap before doing the entire mantle.

I was having a similar problem painting a set of shelves a while back and posted asking for help. The best suggestion was to use a foam brush. Try a GOOD quality foam brush, not the rock bottom cheapest from the big box store. I had much better results with one as compared to the high quality Purdy brush I had been using.

View Nubsnstubs's profile

Nubsnstubs

1249 posts in 1639 days


#14 posted 06-08-2017 09:22 PM

AAANDRRREW, hey man, next time you do something like this with mdf, why not get a laminate with the color and type of finish you desire, and build your project using those materials. You wouldn’t have the finish issue you’re currently having at this very moment and at least for the next 6 months. ............ Jerry Hahaha (in Tucson)

-- Jerry (in Tucson) www.woodturnerstools.com

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AAANDRRREW

210 posts in 1081 days


#15 posted 06-09-2017 02:47 PM

well, it would appear I will have to just embrace the brush strokes. Maybe I’ll tell people its supposed to look like that (I can throw in words like patina and distressed…).

At any rate, I’ll sand it tonight, try a different brush and maybe add a little floetrol to the paint and just live with it. Live and learn I guess.

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