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kwmainer 08-31-2009 07:58 PM

old ceiling damage/stain issue
Nestor and others...

In the 1960's era house where I live, I have a ceiling issue in the kitchen.

2 story house, kitchen first floor - under A/C handler
A/C was added to the house well after the house was built, parts of ceiling in kitchen was lowered to create air space between 1st and 2nd stories for ductwork/returns/etc.
Air handler is on it's side, in a 'doghouse' (it's own gambrel dormer) on back side of house. Right over the kitchen.
About 6 years ago, a new drain line (overflow from A/C pan) was created so the pan wouldn't overflow. Idea was to redirect the water dripping to a non-patio area. New system did not work well, was rerouted back to original set up some months after.
The A/C pan did overflow, and caused water damage to the downstairs ceilings in the dining room, bath, hall and kitchen.
I also have questions about if there's a condensation issue - with condensation off the ductwork dripping onto ceilings in various places as well.

So what do I do to fix this? I DID paint the ceiling with bleach first (to kill mold if any). Then a YEAR later painted the ceiling stains with Kilz - three coats. The stain bled through. Next I painted it with 2 coats of 123 Z. Stain bled through.

Is this normal? I would have thought that FIVE coats of microban, mold killing, primer would have done it... but it hasn't. Husband has checked the a/c, the pan, the overflow pipe - and does so about every 6 months. He makes sure things are clear/clean, not obstructed and such. According to him, we've not had an active leak since this happened (over 5 years ago).

Because the staining and leak area goes through three rooms... if I tear out the ceiling... I'll have to tear it out around several walls. Right? I shudder at the thought. (I'm short... and trying to do major drywall, over my head is a daunting thought... even using scaffold and jack holders.) I simply don't know enough. I don't want to bring down the ceiling in 4 rooms!

Any advice? The kitchen is the worst. The drywall actually looks damaged there and so I figured I'd have to cut out a part and do a 3' by 4' patch or something.

Nestor_Kelebay 08-31-2009 11:05 PM

I'm having trouble believing that a stain bled through an oil based primer (i'm presuming you used the original KILZ primer, which is oil based)(see note below) and a latex primer which is what Bullseye 123 is.

That's cuz when a stain bleeds through a coat of primer or paint, it's because the stain is actually dissolving in the water or mineral spirits thinner of the paint fast enough to spread through the film thickness as it's drying to discolour the surface. You often don't see that happening when the primer or paint is still wet because wet primers and paints are much more opaque when they're still wet than when they're dry. So, water based marks or stains on a wall will typically bleed through water based primers and paints, but won't bleed through oil based primers and paints, and vice versa. To bleed through both, the stain would have to be soluble in both water and mineral spirits, and the only thing I know of that is is glycerine or any alcohol for that matter.

What I would do is this:
Confirm that there is no further leakage of water onto your ceiling by splitting a clear plastic bag open and taping three sides of it to your ceiling in what appears to be the worst area with painter's masking tape. Get a hygrometer (which measures relative humidity) from Lee Valley or any hobby shop. Slip the hygrometer dial side down so that you can read it through the clear plastic, and tape up the 4th side. Now, watch the dial on that hygrometer to see if the humidity of the air behind the plastic increases. If it's increasing, then that water's gotta be coming from somewhere, and I'd conclude there's a leak of some sort, and it would normally be expected to be found directly above the worst part of the ceiling.

If you don't see any signs of continued water leakage onto the ceiling, then I would try a coat of Zinsser's BIN shellac based primer. Shellac is the biggest gun in the arsenal when it comes to blocking stains.

(note below)

KILZ is not much different than an ordinary oil based primer. It has a much faster drying time only because it doesn't use pure mineral spirits as it's thinner. It uses a 60/40 mixture of mineral spirits and naptha as the thinner. Naptha is camping fuel, and in order to keep a good cooking flame going, naptha has to evaporate very rapidly. It's that rapid evaporation of the naptha out of the KILZ that results in the rapid drying time. Really, the KILZ doesn't dry more rapidly than an ordinary alkyd primer because of the mineral spirits still in it. It gets thick and dryer to the touch because the 40 percent naptha evaporates out of it very rapidly.

The whole idea behind having rapid drying times in primers meant to also be used as stain blockers is that the stain has to dissolve in the thinner of the coating and diffuse through that thinner to reach the surface of the coating before it'll discolour the surface and be said to have "bled through" the primer or stain blocker.

The faster the primer or stain blocker dries or gets too thick for the stain to diffuse through it, the lower the chances the stain will be able to do that, and so the better the primer or stain blocker will work.

But, since the stain has to dissolve in the thinner before any bleeding through can happen, normally any stains that are soluble in water won't bleed through oil based primers, and stains that are soluble in oil based primers won't bleed through latex primers. (So I'm scratching my head at your ceiling.)

kwmainer 09-02-2009 01:57 PM

Hi back Nestor...

I used zinnzer (sp?) 123 and Kilz, both acrylic primers. Read through your post a couple times. Hum.

I'm going to ask a question that really exposes my ignorance... lol. I had always 'heard' that if one used an oil based primer or paint... that one could not then paint over it with an acrylic (and vice versa). Is that right?

In this 60's house, the former owners' son slapped cheap, white acrylic paint over everything in the house - ceilings, trim, walls, even tiles. Some of it is peeling off, some has stuck, and some has been sanded off by me. It's an unbelievable mess. I used acrylic primers because I thought I had to. In areas that I've repainted already, I've ripped off the old, now paintsick trim, lightly scuff sanded the walls, primed them then painted them with two to three coats of GOOD acrylic satin wall paint. I've used good ceiling paint for the ceilings.

So on this stained ceiling.... I thought I had to use acrylic. If I use an oil based primer, then don't I need to use oil based ceiling paint? <huh?>

In that one spot in the kitchen where it's the worst, I'm thinking of going ahead and ripping a 3' by 4' chunk out so I can see what's really going on in there. If there's still condensation dripping off the sheet metal A/C ductwork - there's got to be some sort of wrapping or insulation or something I can put around it to stop the water buildup, or hasten evaporation or something. I've done as you've suggested - taped the hydrometer to the ceiling in a bag. I'll let you know what that tells me...


Nestor_Kelebay 09-02-2009 11:44 PM

The rules are:

1. If you're painting:

A) over a latex paint with another latex paint,

B) over an oil based paint with another oil based paint, or

C) over a latex paint with an oil based paint,

you need to sand down the substrate paint for better adhesion if it's semi-gloss or gloss. Anything less glossy, you can just paint right over it.

2. If you're painting a latex paint over an oil based paint, the only time you can do that without sanding is if the substrate oil based paint is a FLAT paint.

Primers are a different ball of wax.

Both latex and oil based primers have huge rocks in them that are almost large enough to see with the naked eye called "extender pigments". These "extender pigments" are what's added to paints to make them dry to flatter glosses like satin, eggshell and flat. Without extender pigments, all paints would dry to a high gloss sheen.

Primers have lots of coarsely ground extender pigments in them, so they dry to a dull matte surface that's easy for ANY paint to stick well to. So, you can paint EITHER a latex or oil based paint over EITHER a latex or oil based primer. That is, if your're painting over a primer, then it doesn't matter what kind of primer or what kind of paint.

Also, if your paint is oil based, then you probably don't need to sand it to roughen it. It's popular to find TSP in the painting aisle because every painter knows that you clean walls with TSP before painting them. This is actually a misconception that's about 50 years old. Before Glidden produced the first interior latex paints in 1959, all interior house paints used linseed oil or Tung oil as the binder, and TSP would etch the surface of drying oil based paints. So, cleaning with TSP helped clean the paint's surface, but mostly what washing with TSP did is etch the surface of the old paint so that the subsequent paint would stick better.

Unfortunately, no one told the painting profession that TSP didn't have the same effect on latex paints. Basically, TSP has no effect on latex paints. It doesn't etch the surface of latex paints. But, even today you can hear painters telling people to wash latex painted walls with TSP prior to repainting them, which isn't great advice. Truthfully, if you're painting over a latex, it's better to use a decent cleaner, like Mr. Clean or FantastiK cuz, TSP absolutely sucks as a cleaner.

I'd definitely try cleaning your oil based paints with a strong solution of TSP, and then rinse the paint off with clean rinse water to see if you can etch the surface of "alkyd" (modern oil based) paints well enough to avoid sanding. It should work since an alkyd resin is really nothing more than a "clump" of drying oil molecules.

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