Detailed Instructions: In this task, you're given a statement, further information available on a particular linked term from the statement, and a question. Your job is to generate the answer to the question by using the information provided. If there is no clear answer obtainable, output 'none'.
Problem:Context: . The process of silvering was once commonly used to produce mirrors, Link Information: When glass mirrors first gained widespread usage in Europe during the 16th century, most were silvered with an amalgam of tin and mercury, but by the 19th century, mirrors were commonly made through a process by which silver was coated onto a glass surface. Question: When was the process that was once commonly used to produce mirrors first discovered?
Solution:
Answer: 16th century