I have mistakenly applied water-based latex primer on my particle
board book case that I am building. Now the areas where I have
applied water-based latex primer have raised grain excessively. I
have tried sanding the raised grain. But I can only sand away the
high spots, and I cannot sand enough to remove the low spots (primer
keeps clogging the sand paper doesn't help either).
Yes, I should have used oil based primer. I have applied oil base
primer in one small area of the book case, and it turns out very nice
after I have sanded the area. But this is too late now because I have
already used the water based primer on most of the book case. I
cannot turn back the clock, I need to find a way to "fix" the problem.
I can try aggressively sanding the surface. But I am afraid that the
sandpaper will keep clogging. And the heat that will generate from
aggressive sanding may not be good for the primer.
I can paint several more coats of latex primer, and hope this I will
fill up the low spots. But I am afraid that this is just wishful
thinking. The primer may simply follow the ups and downs of the
surface, and I may just waste my time.
I can use chemical to remove the primer, and do this over again. But
I am afraid that the chemical may raise the grain even more.
The only way that I can think of is to use a scrapper to manually
remove the primer, sand out the raise grain, and re-prime with oil
based primer. But I think this will be the last resolve.
Is there a better way to deal with this problem?
Thanks in advance.
Because you don't have enough coats.
There is no reason you can't apply an oil base primer over the latex.
No particular reason to but you can.
Uhhh...that's why you sand between coats...to cut down the ridges.
1. I seriously doubt that the primer "raised the grain". Particle
board is inherently rough; not so much to feel but it has a
multiplicity of small hills and valleys. That is true even if you
have sanded it thoroughly.
2. The only way to *ever* get a smooth surface is to fill the valleys.
3. The best thing to fill those valleys is sanding surfacer. It is a
thick bodied, easy sanding paint meant for the purpose. You apply,
let dry and sand until all is flush. It is likely to require multiple
coats before you have a baby bottom surface as you may well sand
through the initial coat(s). Doubt you'll find a good one at paint or
big box stores. You can get it at autobody stores but that is
generally lacquer base and will eat latex/oil.
4. Particle board is a terrible choice of material if you want a good
Thanks for the encouraging info. I will look for the sanding
surfacer, and try it. I guess it is something like the "filler" that
Norm used in one the recent woodworking TV show.
When I said I cannot try oil based primer, I meant I don't want to try
putting oil based primer over the water based primer. I don't know
enough about how different types of primers will interact with each
other. Of course if I could start over with, I would definitely put
oil based primer on the particle board instead of water based latex
Actually, the particle boards that I have primed with oil based primer
(instead of water based primer) turn out very good after I have sanded
them. The problem only has to do with particle boards that I have
primed using water based latex.
I have a feeling that your "sawdust" comments are referring to MDF.
The particle board that I am talking about have many tiny chips in
it. The water based primer has swelled those tiny chips on the
surface of the particle board and create large hills and valleys.
The manufacturer has sanded the surface smooth, and it costs less.
These are the reasons why I am trying to use it to build a book case.
Unfortunately the exposed cut edge tends to be rough, and needs to be
banded with a piece of wood. Because of the added time and effort to
cover the exposed cut edge of the particle board, I think next time I
will use MDF for painted furnitures.
Jay something you might try before starting over is to give the surface a
coat of plain ol sheet rock mud. It sticks to most anything, it dries
fairly fast, is easy to apply, can be sanded to a feather edge and is cheap.
It does shrink and you may have to apply several coats, sanding between
coats. Just go after it much like you would get a sheet rock wall ready to
paint. After the mud job give it a coat or two of a good primer ( I have
had good luck with Kiltz) Then top coat it with the paint of your choice.
Sheet rock mud and paint get along just fine, millions of square feet of
wall surface indicate the combination works.
Thanks for the suggestion of using dry wall compound to fill the low
spots on the particle board. I think I will first try the sanding
surfacer or filler that another newsgroup member has suggested. If
that doesn't work for some reason, I will try the dry wall compound
If the majority wins, my vote would be to toss the particle board in
the dumpster. The material is not the best choice for book cases, to
begin with, as it sags over time. Further the stuff is inexpensive
when compared to say birch veneer, a much better choice for you
application. Also the time needed to rectify exposing the MDF to water
is worth more than the material.
Thanks. Indeed, if I could start this project over with, I would have
used solid wood or plywood, or even MDF. But I don't want to start
this over because the project is almost done except for putting on a
finish. I will apply a coat of filler and sand the surface during
this weekend to see if this helps.
Thanks for pointing out that using MDF is like using particle board
will have the potential problem of getting water damage (in case the
paint comes off in an area of the bookcase and someone leaves a wet
rag or a glass of cold water on it). I only thought of the upfront
cost, and I didn't think of the "maintenance" issue. OK, I will not
be using MDF or particle board for my next project.
You're giving MDF a harsh review. I have used it successfully for
several large projects. I've recently made a 9' x 15' multi-section
shelf unit and a corner cabinet for a massive HDTV.
I first apply a coat of Kilz and sand it down. Then I put on two or
three coats of latex paint, sanding in between and removing dust with a
tack rag. I guess I could use the oil-based Kilz, but I never have,
because it takes too long to dry, and my wife hates the smell. I haven't
had a problem so far.
I'm told that MDF was developed for sign painters. I don't know if
that's true, but a good coat of paint on ALL the surfaces will make it
pretty much waterproof.
MDF _does_ have other problems, like swelling if you don't pre-drill for
I agree with you about particle board.
There is one possibility that hasn't been raised yet; the particle
is wood fiber held by glue and latex paint into a rough surface.
So, get an iron and flatten it. Heat, pressure, rubbing against
a flat surface, and it gets smooth again.
I had a bookshelf blow over during assembly (silly me, did the
finishing outdoors, and stood up a 6' bookshelf), and the plywood
side got a crack. Not too bad structurally, but REALLY ugly.
Painted lotsa white glue into the crack (splinters pointing
everywhich way- REALLY ugly). Let it dry (but it was still
REALLY ugly). Then covered it with aluminum foil and
ironed the damage flat. I have to point at it today or no one
I finally fix the problem by doing these:
o Applying two coats of oil based primer over the latex primer
while making sure that I place the surface horizontally.
o Sanding the surface using 100 grit sand paper.
When I sanded the latex primer, I kept having the sand paper clogged.
Oddly, this time I don't have this problem when I sand the oil based
primer. Not sure if this is a difference between oil based primer or
latex based primer, or this is a difference between a new primer and a
1-year old primer.
I still need to touch up and sand some areas that are more troublesome
than the rest. But now I can see the end of the tunnel.
I don't recall what your planned topcoat is but you should continue
sanding down to at *least* #150 - finer is better - else the scratch
marks in the primer will be painfully obvious after you topcoat.
I am planning to spray oil based paint from a can as the finish top
coat. I use spray paint from a can mainly for the low price and the
fact that I probably don't need to sand the top coat if I spray paint.
I will follow your advice and try finer grit sand paper to sand the
surface before putting the finish coat. Thanks for pointing this out.
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