Walking into Chris Jeffrey's pop-up installation is like entering a prism. Rainbows explode on the wall. Neon green, magenta, electric blue and bright yellow slash in every direction, spilling off the edges of each piece and onto the walls, floor and ceiling. Depth and dimension are no longer sure bets. Beneath the light, ambient sounds thrum in and out, punctuated by a resonant gong. Light-based artworks are hard to show: They require darkness, which rules out group exhibitions and sunlit galleries. That's one reason Jeffrey has installed his project in a vacant Main Street storefront in Montpelier. A sound installation by John Thomas Levee and Graham Sullivan accompanies the light works. The pop-up opens for visitors on Friday and Saturday evenings and can be seen through the window from 6 to 10 p.m. on weekdays through October. The show is untitled, as are each of its eight pieces. To make his work, Jeffrey, who lives in Montpelier, starts with spotlights attached to one or more white panels. Then he holds up a small glass optical filter, which breaks and bends the light into different colors and sends it in new directions. Once he's happy with an effect, he secures the lens in place and repeats the process. This can be quick or take hours. It's experimental and improvisational, Jeffrey said on a tour of the space: "I don't have any kind of a vision for what it's going to be when I start." The industrial optical filters are made in southern Vermont for applications ranging from microscopes to night-vision goggles. For the past several years, Jeffrey was able to purchase cast-off, imperfect filters by the pound. The little pieces of glass in different shapes and sizes alter the light in unique ways, changing its color or trajectory, cutting beams short or sending them across the room. A quarter-turn or slight tilt of any filter can create an entirely new composition. The contradiction between those subtle variations and dramatic bursts of color is at the heart of this work. Visual fireworks hit the eye right away, but close looking rewards the viewer with abundant details. There are tiny peaks and valleys in the brushstrokes of white paint on the panels, where one color hits the highlights and a different one occupies the shadows. Jeffrey uses the space between panels to frame and interrupt strokes of light, particularly in…