Creating the mask involved spreading fluid plaster on the face; the first attempt failed, as Beethoven thought he might suffocate. The second attempt was successful. H. C. Robbins Landon has written that this life mask is "without any question, the most important documentary evidence of Beethoven's features." From the life mask, Klein made a bust of Beethoven; the eyes, hair and clothes were added by the sculptor. During the 19th century, various copies of the sculpture were made, in plaster or bronze.Franz Klein (1779–1840), Lebendmaske Ludwig van Beethovens mit Lorbeerkranz – Anonymer Nachguß der von Franz Klein im Jahr 1812 abgenommenen Maske Beethoven-Haus Bonn, accessed 6 September 2015.H. C. Robbins Landon, Beethoven: A Documentary Study, p11. Thames and Hudson 1970.Franz Klein (1779–1840), Beethoven-Büste, 1812 – Bronzierter Nachguß Beethoven-Haus Bonn, accessed 6 September 2015.
