They worked from the viewpoint that design must restructure an object's function, form and production process, and they applied this maxim to every design that they produced. Castiglioni described this process: "Start from scratch. Stick to common sense. Know your goals and means." 

In the 1950's the Castiglioni brothers cemented their commitment to redesigning objects, with their tractor seat stool, ‘Mezzadro’ and their ‘Sella’ chair made of a bicycle seat. Achille Castiglioni said of the design for the ‘Sella’, "When I use a pay phone, I like to move around, but I also would like to sit, but not completely." These designs drew upon the ‘ready made’ school of art, in which everyday objects are repurposed for the showroom floor. 

During the 1950s and 1960s, they produced a remarkable number of popular designs. Their ‘Spalter’ vacuum cleaner (1956), manufactured by Rem, was made of bright red plastic and was meant to be slung across the user's back with a leather strap. Their lamps, the minimalist ‘Luminator’ (1955) and ‘Bulb’ (1957), employed exposed bulbs, while their ‘Arco’ (1962) was a floor lamp with a long, curved arm extending eight feet from the marble base which had to be moved "by two people inserting a broomstick through the hole in the base." Their ‘Snoopy’ (1967) table lamp, indeed inspired by the cartoon character, also had a marble base, which stabilized the egg-shaped metal and glass shade. Their ‘Toio’ (1962) lamp used a car reflector as its inspiration. Their lighting system for the Montecatini pavilion at the Milan Fair in 1962 featured cone shaped lights suspended from wires. 

The Castiglionis also designed the ‘RR126’ stereo system (1965) which was meant to be a ‘musical pet’, and was considered to be an expressionistic piece. The dials and controls form the shape of a face, with the speakers as ears. This design, for Brionvega, was free standing with castors and folding speakers. 

Achille Castiglioni taught for many years, first at the Polytechnic of Turin, in 1969 and later led a class in Industrial Design at the Architectural Polytechnic of Milan. He received seven Compasso d'Oro awards, a vindication of Castiglioni's method: to have "a constant and consistent way of designing, not a style."