# Problems painting on LDF (light density fiber board)



## Rena (May 2, 2010)

Hi, I've been painting a new set of cabinets this weekend that the carpenter made out of 5/8" LDF (light density fiberboard). He chose this material because its fairly new on the market and way lighter in weight than the regular MDF. He did a good job sanding so I began with spraying on a coat of water based speed primer on both front's, backs - all around. After it was dry, I sanded each door and sprayed with a semigloss waterborne 100 % acrylic formulation. I started by spraying only the back of the doors to see how they would look. What I noticed was that the fibers telegraphed through (bad sign). Anyway, I sanded lightly, cleaned off the dust and sprayed on a second coat of the same material. After it was dry I could still see the fiber profile slightly showing through. So today, before proceeding with painting the front of each door, I covered each with a coat of light weight Spackle. I let it dry, sanded it off, dusted and sprayed on the first coat of finish. Guess what? I can see the fibers!!! I'm going back to give them a light sanding and spray on the last finish coat. *My question is* *...what's going on?? How can I remedy this problem in the future? *


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## Workaholic (Apr 17, 2007)

You could float it with some bondo, wood bondo, or wood filler but this adds to the scope of work greatly. Might be easier if the carpenter changed material (for you that is). Have you tried a heavily bodied primer as if you were trying to reduce the grain of oak? 
More than likely it is just because it is not as dense board, myself I am not a big fan of any mdf.


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## NCPaint1 (Aug 6, 2009)

Painted MDF looks like......painted MDF. You really cant change the look, and to do so would probably take more time and money than it would be worth. Like Work said, change materials, or possibly laminate/veneer or formica them. He could even just make new doors out of pine or poplar that would finish really nice. 

If thats not an option, maybe try lacquer, it should raise the grain less than the acrylics.


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## Lambrecht (Feb 8, 2010)

I have run into the same problem. the best solution I came up with was to sand the crap out it before you spray your first prime coat. Start with 120 grit and work your way up to 400 grit. It is a process that is a pain in the a--, but it will close up the fibers enough that you should be able to get away with a prime coat without much if any fibers coming through.


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## Rena (May 2, 2010)

*Painting Method for LDF*

Thanks everyone for your suggestions. It sounds like the best course of action is to begin (as Lambrecht Painting has suggested) to begin by methodically sanding the LDF from course to fine grit to close the fibers. Then (as Sean has suggested) filling the fibers with a wood filler/bondo type product and using an extra heavy primer (possibly an alkyd based?). Anyway, LDF makes for way too much extra work and personally, I hope to never have to deal with this material again. 

*****



Workaholic said:


> You could float it with some bondo, wood bondo, or wood filler but this adds to the scope of work greatly. Might be easier if the carpenter changed material (for you that is). Have you tried a heavily bodied primer as if you were trying to reduce the grain of oak?
> More than likely it is just because it is not as dense board, myself I am not a big fan of any mdf.


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## johnpaint (Sep 20, 2008)

Sounds like your doing all the right things. Maybe you can let it dry a little longer and very lightly sand as to not cut through the paint film.You may want to try two coat of fast dry primer oil before water base, or do oil all the way.


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## straight_lines (Oct 17, 2007)

LDF is bad for this very reason its just to porous. Maybe a shellac base would work better than the acrylic?


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## TheRogueBristle (Mar 19, 2010)

straight_lines said:


> Maybe a shellac base would work better than the acrylic?



My gut instincts say this would work. Nasty to use, but...

At least a full bodied oil primer, like BM's Enamel Undercoater. What primer did you use any way?


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## Capt-sheetrock (Feb 10, 2008)

want to try something radical ???

spay it with Kilz2 once, then spray it with Kilz2 a second time. Sand it lightly after the second coat. Its ready to be painted.


I know ,, I know,,, it ain't an oil based solution. 

Try it. you might like it,, I do.


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## Rena (May 2, 2010)

*New improved method to paint MDF and LDF*

You're right about using oil base primer - it makes sense as the MDF/ LDF expands like crazy with water based _anything_ (including Spackle). So based on what you've been telling me and with a conversation I had today with another painter here is the NEW - NOW-_ fresh and happening IMPROVED method_ (tell me if you agree). 
Begin by sanding with 400 grit paper to slightly burnish in the fibers. Next seal with a sanding sealer. It dries ultra fast and will raise the grain less than even alkyd base primer. After its dry and sanded the the LDF/ MDF should be now be properly sealed and fibers should be laying as flat as possible. Now we can start painting. I'm thinking the best results will be had with a tinted lacquer (sprayed of course) but painting with a water based paint should turn out really well too. Only problem with a painted finish is that it takes ages to cure. I sprayed 25 doors and used a gallon and a half of paint (tinted a lighter color). The darker the color the longer it takes to cure. Even after 14 hrs. of drying time they are still soft and mar very easily at this stage. The last set of cabinets I painted were a very dark rich red brown and even after 2 weeks they were still soft(ish). Anyway ...what do you think about this method for painting this ever growing in popularity crappy pretend wood? :thumbup:





johnpaint said:


> Sounds like your doing all the right things. Maybe you can let it dry a little longer and very lightly sand as to not cut through the paint film.You may want to try two coat of fast dry primer oil before water base, or do oil all the way.


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## johnthepainter (Apr 1, 2008)

ml campbell has a great brochure on finishing mdf

i think it references their magnalac line.

you can get mdf looking sweeeeeet. it requires a little bit more than a waterbased primer and typical paints though.

youll start out sanding with 400 and work your way up to 2000 no fil paper.

possibly rubbing compound or rotten stone to remove swirls.


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## Rena (May 2, 2010)

Who is ml campbell and how can a person get the brochure? Also what is a magnalac line? thanks!




high fibre said:


> ml campbell has a great brochure on finishing mdf
> 
> i think it references their magnalac line.
> 
> ...


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## DeanV (Apr 18, 2007)

I have thought about using oil primer for MDF panels, but I just do not want the hassle of oil clean up if I can help it. I can deal with the end grain and WB primers. Usually, if I take a power sander and 180# paper to the primer, it takes care of most of the problems on the face of MDF panels, but not always. Hand sanding does not cut it for sure thought on that stuff.


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## straight_lines (Oct 17, 2007)

Yea she is talking about ldf not mdf. Mdf paints really nice, ldf not so much.


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## DeanV (Apr 18, 2007)

I have never seen LDF. Have painted MDF and HDF though.


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