A soaper is a person who makes soap. It is the origin of the surnames "Soper" and (of course) "Soaper". Roads named "Sopers Lane", "Soper Street", and so forth are often so named because historically they were centres for soap-making.
Whilst much soap nowadays is mass-produced by industrial chemical companies, some people still make soap themselves; sometimes out of a desire for a higher-quality or different soap product than can be purchased, sometimes for the sake of keeping the traditional soap-making methods alive, and sometimes as technical avocation, in conjunction with an interest in chemistry or manufacturing.
The hobby of soap-making has enjoyed various eras of popularity, such as during the 1960s. Attention was also drawn to soapers when cold process soap-making was featured in the movie Fight Club. Many hobbyist soapers were unhappy with the way that soap-making was portrayed in the film.