So I'll start off by saying that I'm sorry I have no before pictures, but I made you a video of the sponge-painting process on a piece of foam board.
This room was done twelve years ago and it really is an easy process to paint this effect on the wall. I had never sponge-painted, or even "normally" painted a room before this project. You really don't need any artistic skills in this project either, but don't tell my friends and family that, I like them to continue to think that I have amazing painting skills!
Depending on how your room is shaped, you need to decide which walls are the night-time walls and which walls will become the day-light walls. I decided to split my room diagonally down the center and do half and half. I do caution against painting your entire room in the dark night-time themed colors, as I would think it would optically shrink your room and you would need lot of light in the evening hours to see comfortably. But it is your room--if you want a cozy, dark, cave-like feel to it, then go ahead and paint it all night-time!
Materials and supplies needed:
Blue painter's tape
Pale yellow latex paint for base coat of daylight walls
Light blue latex paint for base coat of night-sky walls
Paint rollers with roller covers
Paintbrush for painting edges and corners
Small craft and stencil-type brushes
Acrylic paint in green, purple, dark blue, deep hue yellow, red paint pen, black paint pen, gold paint pen, glow-in-the-dark paint
Latex glazing medium (can find larger containers of this at the home-improvement stores)
Natural sea sponges
Resealable plastic bags
Plastic bowls for mixing paints
Night sky stencils (or make your own)
Large sheets of thin paper
Graphite transfer paper
Computer printer paper
Yardstick, pencil, and a string
Using your blue painter's tape, tape off your baseboards, your window frames, your doors, etc., on your daylight walls. Also tape off the edges of where the night-sky walls will meet your daylight walls. Prime, if necessary, and paint your walls with the pale yellow latex paint. Apply a second coat if needed and let dry completely.
Partially mix 1 part "deep hue" yellow (it is more light orange/dark gold in color--if you can find a light hue orange, you can use it as well) acrylic paint and 1 part glazing medium in a plastic bowl. By only partially mixing the acrylic paint and the glazing medium, you get bits of stronger color when you sponge the wall. Wet your sponge and wring it out some, but not all, of the water. Dip the sponge in the paint/glaze mixture, then dab the paint onto the wall in an up-and-down motion, all around your pale yellow walls to the edges. With your other hand in the plastic baggie, blot the edges of the color to soften them, or use a clean part of the sponge to blend and mute the sponge's marks. You may need to use the small stencil brush to get into the corners of the room where the sponge can't fit very well. Just dip the end of the stencil brush into the paint on the sponge and dab the brush onto the wall to continue the mottled effect. With the same damp sea sponge, apply a little of your pale yellow latex paint onto the wall in an up-and-down motion and work it in using the plastic baggie method or a clean part of the sponge. Allow the paint to dry.
Using the blue painter's tape, tape off your baseboards, your window frames, your doors on the night-sky walls. Also tape the edges of where the daylight walls meet your night-sky walls. Prime the night-sky walls with the latex primer, if necessary. Paint with the light blue latex paint; allow the paint to dry. You probably don't need a second coat of the light blue paint because of how dark the acrylic glazes are on the wall, but if you feel the need to, apply a second base coat as well. Allow to dry completely.
In separate bowls, mix the dark blue, green, and purple acrylic paints with the glazing medium (1:1 ratio). Using the dark blue paint/glaze mixture and a new damp sea sponge, dab the paint onto the wall in an up-and-down motion, leaving areas of light blue background. Using the same sponge, dip into a second color (purple) and dab randomly over the first areas of color. Continue sponging outward, adding and mixing the colors on the wall. Avoid creating small isolated patches of color, think big and connect masses of the same colors to give a continuous feel to the night-sky. When you come to a corner, use your stencil brush to continue the mottled paint effect where the sea sponge can't fit well. Allow the paint to dry.
Why do I need to add the glazing compound to the acrylic paint before sponging it on?
The purpose of the glazing component in faux finishing/faux painting is to extend the drying time of the acrylic paint and make the paint color more transparent. This helps to be able to continue to blend larger sections together as you move across the wall. This is also the reason that you want to be able to finish at least an entire wall in the allotted time--and not stop halfway through--because the acrylic paint (even with the glazing compound) will eventually dry completely and you will not be able to blend and join the larger sections together seamlessly. You will be left with a darker edge in that case, where the other paint just layered on top of the dried paint instead of blending in with it. If you think you can only do one wall a day, put blue painter's tape on all the other adjacent wall edges, even the finished 'faux'ed walls, to keep the new paint from just sitting on top of the dried paint and leaving behind a funky darker edge.