Painting MDF and plywood - questions

[Sylentwulf]

Still not sure on how much of the cab is going to be plywood, and how much is going to be MDF. But for now...

Painting MDF - I should use an oil-based primer for this since the water based might soak into the MDF? Is this true or false?
If I DO have to use an oil-based primer, can I use a water based latex paint on top of the oil-based primer?
Anything else I should know about priming and painting MDF other then sanding between coats, use a nice roller, etc...?

Would all of the above info apply to the plywood as well? Currently the price difference between plywood and MDF at my local home depot is $45 to $20. The last time I checked it was around $35 to $23. at more than double the cost, I'm going to have to go almost all MDF (3/4" either way)

Any input is great, thanx!

[paigeoliver]

I didn't even prime my mdf, just painted it, came out looking great.

[old school gamer]

You should use oil based primer on MDF or else water based will soak in. YES you CAN use water based (latex paint) over the oil based primer. If you use no primer , it will soak in and take lots more coats of paint,I dont recommend painting without primer. Plywood makes no difference oil or latex works fine,but you should still prime. Oil based paint leaves a nicer finish btw.

[MameMe]

I used regular All Purpose Outdoor Latex(Water Based) Primer and put on two(2) coats of it before I started painting.  I had some lying around the house from a front door project and no problems with the MDF swelling.

[Bgnome]

do people sand between every coat or not?

[ras2a]

I'm using a mixture of PVA (Evostik) and matt white emulsion.  The PVA acts as a sealant and primer (it dries clear) - MDF is very porous and soaks paint up like a sponge!  I'll then probably give it a couple of coats of grey primer (maybe sanding between coats) and finally a couple of coats of satin black.  Lucky really as I have access to a spray booth at work and am gonna borrow my mates compressor and gun.  hoping that spraying my cab will negate the need for much sanding though!

cheers

Craig

[greywolf22]

I used a water based primer and paint on my plywood cab.  Worked very well, and yes I did sand between every coat with a very fine sand paper.  

[DanteBK]

I'm about to start painting my MDF cabinet and had the same question. I've heard enough people say, "don't, whatever you do, use water-based primer because it'll mess up the MDF," and enough people say, "I used water-based primer on MDF with no problem," so here's my question:

Is the water-based primer messing up MDF thing just a sensible theory or has anyone actually had their cabinet messed up by this?  

[sirwoogie]

Slightly off-topic question. I can figure it out for myself I guess, but I'd rather see what the community has to say:

If I do countersunk holes on the outside (ala UAII), fill with wood putty and sand down, would putting primer/coats on be sufficient to hide it completely? I've actually never used wood putty, and I never seen it done without leaving some evidence. That more or less sets me in the direction of the construction for the cab.

[Sylentwulf]

I had the same concern about countersinking and woodfilling from the outside, so I'm using a ledger system from the inside instead. I HAVE used woodfiller, and theres no way in hell I'm gonna fill 100 tiny screw holes on the finished outside of the cab.

The reason they suggest doing it that way is because they also suggest using laminate, which would completely cover any imperfections anyways.

[MameMe]

I drilled from the outside and filled with putty, and YES some spots where I didn't sand perfectly came out a little "Rough" and bumpy.  I don't think it will be a huge deal for me personally because side art will eventually cover most of it.

All in all it doesn't look like crap, its just rough to the touch in a few bad spots where I must have gotten carried away with the sanding.

[rdagger]

Here's another vote for water-based primer and latex paint.  I sprayed Glidden Gripper water based primer onto 5/8" MDF.  There was no swelling and I only needed 1 coat of primer.  They I sprayed 3 coats of satin black.  Next is a clear coat.  It's been about 2 weeks and everything looks great.

[greywolf22]

I actually replaced a number of screws in my cabinet (since the one's that were there stuck out and did NOT look good at all), counter-sunk them, wood puttied over them, sanded, primered, sanded, painted..etc.  And it is very difficult to tell where the screws are...granted I have a large number of coats of paint on my cabinet (very long story), but if you sand the wood putty down to be fairly flush with the cabinet it should be very difficult to see.  Not sure if that answers the question or not though.

[Darkstalker]

Lifted from this website (http://www.howelumber.com/paint.latexoil.htm):

OIL: Oil based paints, also known as "alkyd" paints, are generally thought of as a more penetrating paint. The oils that the paint uses tend to go deeper into the pores of the surface you paint, and bond at a deeper level. The down side is that they can yellow over the years, and that in order to clean it up, you need to have paint thinner, turpentine, or other mineral spirits at hand. And just because oils penetrate deeper into the substrate (i.e. into the wood or whatever), it does not mean that an alkyd paint will never peel. Most paints will peel if water gets under them, or from weathering through time.

LATEX: Latex based paints bond to the surface, and so are useful for a number of applications. They provide a good seal at the surface, and maintain their color well through time, without the yellowing alkyd paints are known to have. They clean up with water, and dry in a relatively short amount of time. These are the main reasons so many people have opted to use latex paints, especially inside their homes.

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My advice:  Fill in any holes with putty, get yourself a nice orbital sander (NOT a belt sander) with a medium to light grit paper to smooth it all out, then stick with the latex paint.  Oil looks nicer once it's done, but it's a pain to clean it up.  I've never painted on MDF, but I've never had a problem with water absorption using Latex paint, so I see no reason to primer since the cabinet is (I assume) indoor use only.