Painting Problems

[rykruger]

Hey everyone.  Ive been reading the boards for awhile and have hit my first problem.

Im building a UAII cab with MDF.  I've got everything assembled and am finishing the paint job.  I primed with an oil based primer, and have put a few coats of latex black paint on top.  The paint doesnt seem to be sticking really well.  A fingernail across it will remove the black paint leaving white primer.

Looking back I wish I had used an oil based finish, even though Ive read here and on the primer instructions that a latex should be fine.  Is there anything I can do now?

Ryan

[Hoagie_one]

i never use oil based paints...just too nasty to deal with and hard to clean up.  Also makes it a pita if you have to strip and start over

[RayB]

Hoagie, how exactly does it turn into a wrap sandwich?

[Hoagie_one]

um....magical trevor?

[rykruger]

Of course if I had to do it over agian, I would go water based, but I read on this board somewhere that people said not to use water based primer on MDF.  I have ince read that i not a problem.

Ryan

[DrewKaree]

Of course if I had to do it over agian, I would go water based, but I read on this board somewhere that people said not to use water based primer on MDF.  I have ince read that i not a problem.

Ryan

are your primer and paint manufacturers the same?  If not, I'd say get the same brand paint.  Also, tell us what the cans say - both paint and primer - that may shed some more light on the problem.

water based primer wouldn't be a problem, but the MDF soaks it up more, and it may swell the stuff...to me, that may be a problem, but it depends on what constitutes a prooblem to a person

[rdagger]

You might have bad paint.  Good quality paint can make a big difference.  Be careful at Home Depot, some of their paint is terrible.  I had some problems with their Behr latex paint.  I've had good luck with Dunn Edwards.

Weather conditions can also affect paint.

I just completed a MDF cab with water-based priming and coating with no swelling.  I used a HVLP sprayer.

[whammoed]

How long did you wait for it to dry?  I have painted furniture that was primed first and the latex paint can stay kind of rubbery for quite a while.  I found it best to just leave it alone and be careful with it while it cures...weeks maybe.  Ends up being a pretty good finish.

[Hoagie_one]

How long did you wait for it to dry?  I have painted furniture that was primed first and the latex paint can stay kind of rubbery for quite a while.  I found it best to just leave it alone and be careful with it while it cures...weeks maybe.  Ends up being a pretty good finish.

That was the problem i had with my bartop.  I started moving it around too soon and i got a few spots that scraped up.  

[jerschwab]

I'm facing this problem now too... oil based primer, latex paint.  I'm scared to touch it, because it will peel much too easily.  I thought it was maybe because I didn't send good enough, but I'm not sure.  Probably low quality paint.  Dang, I'll just have to be careful moving it into it's resting spot.

- Jeremy

[Darkstalker]

"I had some problems with their Behr latex paint."

That's weird, I've never had a problem with Behr.  Glliden paint is horrible, but Behr has always worked excelent when I've painted rooms.

The only time I've seen latex paint strip off that easily is when you try painting over gloss without stripping it first with like TSP or somthing.  Latex paint should go just fine over oil, just so long as it isn't glossy (Which primer isn't).

[RayB]

You'll also get problems if you sanded your primer coat (or it collected dust somehow). Also painting many coats too soon creates one thick coat that can easily peel off. You gotta do one thin coat and let it thoroughly dry first. Then do another...

[MiKman]

I was always taught that you cannot paint latex over oil. but oil will paint over latex.  someone once told me that when repainting something and in doubt about what's already painted then buy oil...  maybe your problem is mixing oil and latex.  I could be wrong tho  

[Darkstalker]

I was always taught that you cannot paint latex over oil. but oil will paint over latex.

Actually, you've got it backwards.

[rdagger]

That's weird, I've never had a problem with Behr.  Glliden paint is horrible, but Behr has always worked excelent when I've painted rooms.

I used Glidden gripper latex primer and then covered it with Behr black latex.  The primer went on well and dried quickly.  After a day of drying, I applied the black.  The black was very difficult to get a smooth finish.  I even tried several combinations of Flowtrol without any improvements.  It took forever, because the black stayed sticky for days and required a lot of sanding.

[exibar]

I've found that you cannot rush things with Latex paint.  If you try and sand or make use of a surface that you've painted with Latex paint less than 72 hours ago you'll have peeling problems.  It's almost like a sunburn, but with paint peeling....

  Give it at least a week before doing anything with that Latex painted surface before doing anything to it.  You will probably find that it will take a couple weeks to completely cure before it's a durable surface...

Especially if it's very humid out, like down in Florida or up here in New England during the summer months.... It will take much longer for the paint to fully cure when it's really humid out, even if it's indoors....

  At least that is what I found.

[Darkstalker]

That's one of the two main benefits of oil paint.  Humidity doesn't slow the drying process nearly as bad, and oil will "smooth out" better.  You tend to see brushstrokes more with Latex than you do with Oil.

Oil is just a serious PITA to clean up after though...

[RayB]

Oh now I get it. When Hoagie used the word "pita" i thought it might be a type for "pity".

tee hee. Now I know it means Pain in the...

[froggerman]

Oil is just a serious PITA to clean up after though...

I use oil paint a lot of the time and although I agree that it isn't always as easy to clean up as latex paint it isn't that bad either if you are just a little bit careful. The biggest help for me is that I line my roller tray with plasic wrap before I use it. When I am done I just remove the plastic wrap and I am done. I wrap the roller in plastic wrap until the next day/coat. When I am done I throw it out. You can also put the wrapped roller in the freezer and it will stay useable for quite a while. One thing that I have found is easier with oil than with latex is cleaning the roller handle and paint stick. I can just take a piece of paper towel and wipe them clean. Don't even have to use paint thinner. I have found in the past that latex paint will dry before I am finished painting and it takes more work to clean.

The most important thing to me is use the paint that is the best for what you are doing, either oil or latex. I use both latex and oil primer for example.