Wallpaper is paper, and when paste is applied to the back, the paper gets wet and expands a little. When it hits the wall, it dries – and often that means it will shrink, even if just a tad. That will leave minute gaps at the seams. If the paper is dark and the wall or the substrate are light , you will most likely see white gaps at the seams.
Some manufacturers combat this by printing dark patterns on a darker substrate. This is what you see in the photo above. But it also helps to color the edges of the wallpaper with a corresponding color of chalk. (You can’t use ink, because ink will bleed and discolor the wallpaper.)
Sometimes you can go back and color in the seams with hobby paint or chalk, which sounds simple but actually takes some technique and finesse, to color the areas adequately and avoid staining the paper.
Painting the wall the color of the paper is a thought, but not as feasible as it sounds, because wallpaper wants to stick to wallpaper primer, not paint. And I’ve seen paint lift off the wall when the wallpaper dried and put tension on it – so, not using that trick again.
Paint with a clear wallpaper primer over it is another idea – but it adds an extra day (or two) and more labor and material costs.
What I did in this case, was to try different pasting methods. This wallpaper, from the Historic Homes Collection by Thibaut, is pre-pasted and engineered to be run through a water tray to activate the paste on the back of the paper.
This method works super with most of their colors. But, because the water tray adds a lot of moisture to the wallpaper, the amount of expansion and then shrinkage results in tiny gaps at the seams – not a big deal with a white or light-colored wallpaper. But with this black paper, it was showing too much white at the seams. Yes, a 1/64th” is too much, when you are looking at white between black.
So instead of running the paper through the water tray, I experimented with pasting the back of the paper. I knew this method would allow the paper to expand less, dry faster, and shrink minimally.
But wallpaper that has a thin layer of pre-paste on the back does not respond well to the installer applying paste to the back on top of the pre-paste. You are greeted with a thick, dry, gummy mess that is hard to manipulate on the wall.
There were also a lot of bubbles and blisters under the surface. Yes, you can be assured that these will disappear as the paper dries – but it sure makes you nervous while you are looking at them!
Spraying the back of the paper with water from a mister didn’t work, either, because the spray bottle spread water unevenly, water sloshed onto my work table, and there was nothing to enhance the “stickiness” of the manufacturer’s pre-paste.
After experimenting, what worked best was to apply paste to the back, full strength, and then quickly spritz the back with water and roll it around, to thin down the paste I had just applied, and to add enough moisture to activate the pre-paste.
The wallpaper strips with this pasting concoction were thick and muddy and difficult to maneuver, but the drier paste did lock down at the seams more quickly. I didn’t have issues with shrinking or gapping seams after I started using this pasting method.
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