Posts Tagged ‘tar’

Mirror Tar – Bad For Wallpaper

January 24, 2021

Mirrors are commonly attached to walls with mastic – a sort of tar adhesive. When installing this new mirror, the workmen got some of the tar smeared on the wall below.

This is bad. Tar, like many other substances, will bleed through paint and wallpaper.

So this stain will need to be sealed over with a stain blocker. Or, better, cut out of the wall entirely, and then the damaged wall will have to be repaired. Learn more on this by doing a Search in the upper right corner.

Fixing Weird Things That Happen To Wallpaper

December 6, 2020

The top photo shows a stain on the wallpaper that is probably related to a rain or hurricane event a few years ago.

Water stains (and also other substances, like rust, blood, ink, oil, tobacco, tar, cosmetics, and more) will bleed through wallpaper. So, before patching the area, it is imperative to use a stain blocker to seal the problem. My favorite is KILZ Original oil-based.

KILZ will seal off the stain all right. But wallpaper won’t stick to it. So, in the third photo, you see where I have primed over the KILZ with a wallpaper primer (tinted light blue, for visibility). It’s not necessary to prime the entire wall area to be patched, because this type of wallpaper will stick to itself with just plain old adhesive.

The striped pattern made for an easy repair. I took a straightedge and sharp razor blade and trimmed along the striped design, creating a long skinny patch. See fourth photo. You can also see the strip pasted and booked (folded pasted-side-to-pasted-side).

Once that sat and relaxed for a few minutes, I took it to the wall and appliqu├ęd it over the damaged area, going the full height.

There was a very slight color difference between the paper that had been on the wall for 20 years and the paper that had been in a dark closet. Had I placed the white area of the patch next to the white area on the existing paper on the wall, the color difference would have been noticeable. But trimming along the blue stripe gave the eye a logical stopping point, and so the color difference is not detectable.

In the finished photo, you would never guess there had been anything amiss with this wall.

I used this same technique to patch over the bug-bite holes in yesterday’s post.

And another good reminder that it’s always best to order a little extra wallpaper, in case of the need for repairs later. Store the paper in a climate-controlled space … not the garage or attic.

The wallpaper is by Schumacher, and appeared to be an old-school pulp paper material.

Rust From Water Damage Will Stain Wallpaper

August 11, 2020

Look to the right of the can. Notice the tiny spots of red. This is rust, and rust is bad because it (along with certain other substances, like ink, tar, oil, tobacco, water stains, wood sap (knots), mold, mildew) will bleed through wallpaper. Maybe not immediately, but, over time, it will work its way through the primer and the paper and to the surface, leaving a spot that cannot be washed off.

Actually, there was a whole lot of rust along the entire height of this wall’s corner. An air conditioning leak had kept the drywall wet for a period of time, and rust had formed along much of the metal corner – called a “bead.”

I skim-floated over the affected area with joint compound, and that buried the rust … for a while. But rust (and other substances), will eventually work their way to the surface, leaving spots on the wallpaper.

So a stain blocker was called for, which will prevent any stains from bleeding through. For this I love KILZ – but only the “Original” oil-based version. The water-borne products just don’t measure up

Some reasons I skim-floated over the area was to provide a buffer space between the rust and the sealer in hopes that the rust would not make it all the way up to the surface, to create more material over the very corner itself that could soak up the sealer, and because the stain blocker would soak into the porous smoothing compound more so than to the sharp corner of the metal bead.

Mirror Tar Bleeds Through Wallpaper – Prevention

June 18, 2020



The owner of this newish home in the Woodland Heights (Houston) had her handyman remove the powder room mirror and its surrounding built-in wooden frame. Mirrors are often adhered to the wall with mastic, a tar-like substance. When the mirror comes off, some of the tar residue invariably remains.

In the top photo, you can see where removing the mirror took the blobs of mastic along with it, as well as round sections of the drywall. But there are small smudges of tar still remaining on the wall.

The problem is that tar (among a lot of other substances) will bleed through wallpaper (as well as paint, and a lot of other materials).

There are stain blockers like my beloved KILZ Original Oil Based, BIN shellac based, or others, that are designed to block these stains. But I don’t trust them. For water, rust, blood, wood sap, etc., yes. But for oil-based substances like tar, I want more assurance. The best way to prevent bleed-through is not to cover the stain, but to remove it.

So I take a Stanley knife and cut into the drywall and then peel up the top layer of drywall, taking along the offending tar residue.

So now the dangerous tar is gone. But you’re left with torn drywall. This is bad for several reasons. For one thing, you have an uneven surface that will look bad under the new wallpaper (or paint). And since the top, protective layer of drywall is gone, any moisture (such as from wallpaper paste or from latex paint) will penetrate into the torn paper layer – which will swell and cause bubbling.

All of which looks pretty bad under wallpaper or paint.

So I used the product Gardz to seal the torn drywall. It is formulated to soak into the paper; then it dries hard and acts as a sealer and moisture-blocker. It won’t block stains, but it will prevent moisture from penetrating the paper and causing bubbling.

Once that was dry, I skim-floated over the entire area with joint compound. It looks rough in the photo, but once it’s dry, I’ll sand it smooth. Then I’ll give it another coat of the penetrating sealer Gardz. See last photo. Once that is dry, I’ll cover it with a coat of Roman’s Ultra Prime Pro 977 wallpaper primer, when I prime the other walls in this powder room.

All of these various products do take a while to dry, especially the joint compound as thick as I applied it. So I went to this job site a few days before the install date, to do the initial prep, so it would have plenty of time to dry before I come back for the final prep and wallpaper hang.

Mirror Removed – Ready for Wallpaper? NOT!

March 20, 2018


A mirror had been glued to this wall with mastic adhesive (a tar-like substance). When the mirror was pulled off the wall, the adhesive pulled some of the drywall along with it, and in other places it left some of the tar on the wall. Then someone skimmed over the surface with joint compound.

The wet joint compound caused the torn areas of the drywall to absorb moisture and ripple, and the tar worked its way through the joint compound.

Both torn drywall and tar are problems under wallpaper. The ripples from the torn drywall will show under the new wallpaper. And moisture from the wallpaper paste is likely to make the bubbles larger. The black mastic (tar) will bleed through the wallpaper, creating black spots.

If I had been there when they removed the mirror, I would have taken a utility knife and cut the globs of mastic completely out of the wall. Removing it is preferable to trying to cover it up. Yes, this would have torn the drywall, opening it up to wrinkling when it gets wet with primer or paste.

But the penetrating sealer “Gardz” is designed to fix torn drywall. It dries hard and impermeable, so moisture cannot get through. No worries about bubbles or wrinkles! The cut areas could then be skim-floated over and then sanded smooth.

But since I didn’t get to prep from the beginning, I inherited this wall in the top photo, with torn, wrinkly areas, and with tar bleeding through the joint compound.

To prevent additional bubbling, I coated the wall with Gardz. Once that was dry, wanting to both smooth the wall and create an additional barrier to contain the mastic stains, I skim-floated the entire wall, let dry, sanded smooth, and sealed again with Gardz.

Gardz doesn’t protect against stains, though. So, to keep the mastic from bleeding through, I coated the wall with KILZ Original oil-based stain killer and blocker. This worked better having the joint compound under it, because when I’ve put KILZ directly on mastic adhesive, the two petroleum-based products simply melded into one another, and left us with the very real potential for bleeding through wallpaper (or paint, BTW).

So the KILZ should have effectively blocked any stains from the mastic. But the new problem is that wallpaper paste will not stick to modern, EPA-approved, oil-based products. Plus, I was worried that a little of the black tar might still find a way through.

So I skim-floated the wall again, creating yet another layer that would bury those tar stains. After that was sanded smooth and wiped free of dust, I applied another heavy coat of Gardz.

All this took a long time, but it’s good assurance that bubbles will not be seen under the new wallpaper, and that no black spots will grow on its surface.

Covering Rust – Rust Bleeds Through Wallpaper

April 13, 2016

Digital Image

Digital Image


The dark red stain on the edge of that outside corner is rust. It is coming from the metal bead used to define the corner when the house was built. The only problem is, in a steamy bathroom with poor ventilation, these metal beads are sometimes prone to rust.

And rust bleeds through wallpaper.

Before I started hanging the new, pastel-colored wallpaper, I had to block off the rust stains. Nothing tackles this job better than the original oil-based KILZ Original. I’ve taken a small brush and applied KILZ to a half-inch wide strip that runs the height of the wall. It dries in about an hour, so paper can be hung fairly quickly.

Other substances can stain wallpaper, so KILZ is good to have on hand. KILZ also seals off water stains, oil and tar, ink and markers, and odors, like smoke from cigarettes or fire.