Problems galore painting Flexy (aka HELP!) (1 Viewer)

[Andy Kim]

Hi!
I primed my MDF boards with plain black spray paint and then sanded. I did this about 3 times for all my boards.
I then went to spray my first board with gloss black spray paint. It worked well.
So far so good....now the trouble.
For the next 4 boards, the gloss black spray paint would stick on the top of the boards BUT would ABSOLUTELY NOT bind with the 4 sides of the boards. I would spray the gloss black paint on the sides but about a minute later, the paint would all be gone as if I did not even paint it at all. The sides were dry to the touch in a matter of a minute. It just evaporated or drooled down. I don't understand why the paint won't stick to the sides. Its almost like the "oil in water" effect...the sides refuse to mix or absorb any paint.
I did wipe the boards down with a damp cloth after sanding but that was after atleast a coat of black primer paint. Could that have ruined it? And I don't understand why my first board worked but the rest of the 4 didn't. The only difference is that I sanded the 1st board in doors and the other 4 I sanded outside in below or near zero temps. Could the cold temperature have done something to it? I'm clueless!
I'm thinking of buying some gloss paint in a can (instead of spraypaint) and then rolling it on but I'm not sure whether the same thing will happen with roll on paint. Have I ruined the boards forever?
Any thoughts would be appreciated!
Thanks,
Andy

 

[Bill Harada]

Andy,
It sounds more like your three shelves don't have the edges properly sealed, which is resulting in the paing being absorbed into the MDF as if it were a sponge. Perhaps you sanded the edges of these three shelves more than the first? If the paint were'nt sticking it would be dripping off the edges instead of leaving it dry.
I'd try brushing some sandng sealer on the edges. It's a clear coating used to close the pores in the wood so that the paint doesn't get absorbed.
Bill

 

[Chad Anson]

Yeah, that's a common problem with MDF. The sanding sealer should do the trick. Alternatively, you can get a role of veneer edging and glue it to the sides. The veneer should take the paint just fine and is relatively inexpensive.

 

[David A. Frattaroli]

Bill hit it right on the head. MDF edges are a bear to seal.

 

[Robert Fellows]

You should always prime prior to painting. In this case, I'd recommend spraying it with shellac first, a couple of times, then paint.
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Bob
p.s.: This advice is worth exactly what you paid for it...

 

[ken thompson]

If I were to build one I would certainly want to tack some molding around the edges to make it nicer and give the appearance of thicker shelves.