Assertion: lead pencil's lead | /r/HasProperty | 10% antimony
Facets:
Source sentences:
text: The process is similar to that of primary production in either a blast furnace or a rotary furnace, with the essential difference being the greater variability of yields: blast furnaces produce hard lead (10% antimony) while reverberatory and rotary kiln furnaces produced semisoft lead (3–4% antimony).