Gouache (rhymes with squash) paint is my medium of choice for coloring bolt-ends, as well as for post-installation seam coloring and touch-ups. I was introduced to it by an Ohio paperhanger named Dan Falter, who gave a presentation on its use at an NGPP convention several years ago.
From Wikipedia: “Gouache paint is similar to watercolor but modified to make it opaque. A binding agent, usually gum arabic, is present, just as in watercolor. Gouache differs from watercolor in that the particles are larger, the ratio of pigment to water is much higher, and an additional, inert, white pigment such as chalk is also present.” In layman’s terms, gouache is a watercolor mixed with chalk, and it has two advantageous characteristics for our purposes: it dries dead flat, and it’s non-permanent.
Prior to finding out about gouache, I relied on felt markers, chalks, and colored pencils to make white edges disappear from the seams of dark papers. The results were mediocre, and sometimes poor. A split seam or white edge could be camouflaged, but as often as not it was obvious that the wallpaper had been tampered with: markers often made the edge too dark, chalks were too dusty, and colored pencils were rarely an exact color match.
Along came Winsor & Newton gouache, carried by all professional artist-supply stores, as well as by most big-box craft stores, such as Michael’s. Armed with Dan’s list of the eight or ten optimum colors to keep on hand, I shelled out about $100 to make my own kit, which included a pro-quality ‘flat wash’ brush. Gouache is pricey, and so are good artists’ brushes.
Winsor & Newton Designers Gouache comes in many shades, but you don’t have to buy the whole collection. If you have a good eye for color mixing, you can get by with a basic kit with which to mix pretty much any color. My gouache kit contains the the following: One each of the larger size tubes of Lamp Black and Zinc White. I use way more of the white and black than of any color, so I find it economical to buy the larger size tubes for those two items. Of the smaller tubes, I have Primary Yellow, Alizarin Crimson, Primary Blue, Yellow Ochre, Raw Sienna, Burnt Sienna, Raw Umber and Burnt Umber. With these I can match just about any wallpaper ink that I come across.
Here are some examples of bolt-ends colored with gouache. The wallpaper is a Cole & Sons non-woven.
My method is to mix the gouache to the color that I need, and then I add water to thin it down to the consistency of dairy creamer. I use small, glass mixing bowls. Here is a black O&L being colored. I leave the rolls mostly wrapped, opening only the ends of the rolls. This keeps the paper rolled tight and minimizes the gouache bleeding onto the face of the paper — which isn’t much of an issue anyhow, since gouache is non-permanent and washes off with water. That’s the beauty of gouache; it gets absorbed by the white edge of the roll without staining the face of the paper. In the event that it does get on the face of the paper, it can be washed off later, even after it’s dried. Try that with ordinary acrylic paint.
For seam coloring (making a white seam disappear after the paper has dried), the mixing method is the same: color-match first, then thin with water to the desired consistency. I use the same flat-wash brush as I use for bolt-end coloring to apply the thinned-down gouache to the seam. Since the medium is non-permanent, it doesn’t matter if you get gouache on the face of the paper. In fact, it’s unavoidable unless you wish to apply the gouache with a hairline brush. I just paint the gouache into the seam liberally, and the white edge of the sheet absorbs the color. After the gouache has dried, I take a well wrung-out microfiber towel and wash the dried gouache off the face of the paper. I use a side-to-side wiping motion, washing across the seam rather than with the seam, thereby washing the dried gouache off the wallpaper’s face without disturbing the gouache in the seam. I rinse the rag frequently as I proceed.
In the photos below, I was asked to repair a black Nina Campbell wallpaper that had shrunk at almost every seam and every inside corner. The job was brand new. The first photo shows one example of what the entire room looked like. The rest of the photos are the ‘during’ and ‘after’ shots. For seam coloring, the gouache should be completely dry before it gets wiped off, otherwise it won’t have time to set into the white seam. The gouache dries as a chalky, dead-flat residue on the paper, and then it reconstitutes when you wash it off with a damp rag. It usually takes three to five minutes for the gouache to dry, depending on job conditions.
This is my gouache kit. It’s an old wooden cigar box, and it’s seen better days. I’ve gotten a lot of mileage from it. I’m not the best color mixer in the world, and so when I finally get the right formula to match a difficult color, I’ll paint a swatch of it on the inside of the lid and write the proportions underneath it: “1/2 black, 1/4 white, 1/4 crimson, 1/4 yellow ochre.”
Since gouache reconstitutes with water, I’ll sometimes leave a leftover mixture to dry in the mixing bowl. If I come across that color again, I just have to add water to bring it back to life in the bowl.
Gouache can also be used to touch up scratches and tears to wallpaper, as well as to make switch-plate screw heads disappear.
It’s been said that the skill of paperhanging is to hide the skill. Hopefully you’ll be able to use gouache to your advantage on those jobs where skill alone doesn’t cut it.