Type C: for pianos from c. 1820 to c. 1840; a hard-drawn iron with a carbon content. Recommended maximum practical tensions are:

 0.40mm                   15.7kg                                     0.75                        39.2

0.44                         18.4                                         0.80                         42.5

0.48                         20.8                                         0.85                         45.7        

0.52                         23.5                                         0.90                         48.9

0.56                         26.4                                         0.95                         51.7

0.60                         29.0                                         1.00                         54.6

0.65                         32.4                                         1.07                         58.5

0.70                         35.8                                         1.15                         62.6