Following are a number of back-translations as well as a sample translation for translators of Proverbs 27:21:

• Kupsabiny: “The goodness/quality of gold and silver is known when it is brought through fire,
  but the goodness of a person is known when he is praised.” (Source: Kupsabiny Back Translation)
• Newari: “are also never satisfied.
  Like gold and silver are tested
  by putting them in the fire
  people are also tested by being honored.” (Source: Newari Back Translation)
• Hiligaynon: “As gold and silver are-tested if it is pure or not by fire, our (incl.) lives are tested by the praising of other people to us (incl.).” (Source: Hiligaynon Back Translation)
• Kankanaey: “Gold and silver are verified/confirmed by-means-of flaming fire, a person moreover, his personhood (i.e., what kind of person he is) can-be-known by-means-of his-being-praised.” (Source: Kankanaey Back Translation)
• English: “Workers put silver and gold in a very hot furnace to burn out what is impure,
  and people learn what we are really like when they see how we react when people praise us.” (Source: Translation for Translators)