In spite of the name, pencil leads do not contain the toxic chemical element lead, but are typically made with graphite and clay, or plastic polymers. 尽管名称叫做“铅”,铅笔铅不包含有毒的化学元素铅,而通常用的是石墨和粘土,或塑料聚合物。 LASER-wikipedia2 The first patent for a refillab...
Mixture for manufacture of pencil leadsdoi:US2682476 ANURNBERG GEORG LOYUSUS2682476 * Nov 21, 1950 Jun 29, 1954 Staedtler J S Mixture for manufacture of pencil leads
Although graphite core in pencils is still referred to as lead, modern pencils do not contain lead as the “lead” of the pencil is actually a mix of finely ground graphite and clay powders. This mixture is important because the amount of clay content added to the graphite depends on the ...
• Color pencil leads, also used by artists and popular with children and students, are made through a similar process of creating a blend of pigment, china clay and wax that is extruded into a lead. Some basic sets of color pencils come with 12 or 24 colors per carton, but other hig...
are graded on the Euro-pean system. This system of naming used B for black and H for hard; a pencil’s grade was described by a sequence or successive Hs or Bs such as BB and BBB for successively softer leads, and HH and HHH for successively harder ones. Then the standard writing pe...
are graded on the European system. This system of naming used B for black and H for hard; a pencil’s grade was described by a sequence or successive Hs or Bs such as BB and BBB for successively softer leads, and HH and HHH for successively harder ones. Then the standard writing penci...
are graded on the European system. This system of naming used B for black and H for hard; a pencil’s grade was described by a sequence or successive Hs or Bs such as BB and BBB for successively softer leads, and HH and HHH for successively harder ones. Then the standard writing penci...
The writing cores of pencils consist of a tightly pressed, uniform mixture of minute particles of different materials. Lead cores contain graphite, colloidal refractory clay (bentonite), a binder (tragacanth or pectin cement), and fats or wax. Colored leads are made of pigments, kaolin, bentonite...
Individual pencils cut from the sandwich are ready for further processing. Any pencils with defects, such as uncentered leads or chipped wood, are discarded at this point. Next, each pencil is painted in a machine receiving from 4-10 coats of lacquer, depending on the desired quality of the...
United States Patent US2682476 Note: If you have problems viewing the PDF, please make sure you have the latest version ofAdobe Acrobat. Back to full text