The "box iron" was composed of a flat-bottom box and a handle. Hot coals, bricks or other heating elements were placed inside. Such a design removed the need for a protective layer of clothing between the garment and iron because the iron retained a clean surface. The box iron remained the standard for several hundred years.

Metal technology began developing in the 1800s, hastening the evolution of the smoothing iron. Flatirons could be heated atop cast iron stoves, making the job much easier and cleaner than fire. By 1870, wooden handles were used, preventing users from receiving burns, as wood does not retain heat in the manner of iron.