Littleton retired from teaching in 1976 to focus on his own art. Exploring the inherent qualities of the medium, he worked in series with simple forms to draw attention to the complex interplay of transparent glass with multiple overlays of thin color
Allowing the pull of gravity to stretch and bend hot glass while on the blowpipe or punty led Littleton to his "Folded Forms" and "Loops" series, which continued until 1979. His "Eye" forms, also from the 1970s, take the form of concentric cups of various colors in diminishing sizes that nestle one inside the next.
Perhaps Littleton’s best known body of work is his "Topological Geometry" group of series, made between 1983 and 1989. Included under this heading are his signature "Arc" forms and "Crowns," as well as his late "Lyrical Movement" and "Implied Movement" sculptural groups. In 1989 chronic back problems forced Littleton to retire from working in hot glass.Wikipedia