Wilhem Braun-Feldweg, a leading post-war industrial designer, invented these opal glass lamps in 1959. Braun-Feldweg based his design on the drop-like bubbles that are formed in glass-blowing. In his own words: "First a round ball appears, then this turns under natural pressure into an oval droplet. Seen this way, the drop is the most obvious natural shape for all glassware." In the 1960s these lamps were produced in the Peill&Putzler glass-blowing works; after a break, they are now being made again in a Czech glass-blowing works, and are of matt Triplex opal glass, mouth-blown as in the old days.

Wilhelm Braun-Feldweg, one of the most influential industrial designers of the post-war period, based the teardrop shape of these opal glass lamps, designed in 1959, on the physics of glass blowing: "The 'Kölbel' forms like a soap bubble on the pipe: first a ball, then, yielding to its weight, it turns into a drop. The drop shape is therefore the natural and self-evident shape of the glass body." In the 1960s, the lamps were produced in the Peill & Putzler glassblowing workshop; now they are being produced again in a Czech glassblowing workshop: mouth-blown, like the originals, from frosted triplex opal glass.