Descrizione
Dustless chalk was introduced as an alternative to the traditional plaster chalk because of its powder scattering when writing and the possibility of the powder being harmful to the human body. Dustless chalk, made by adding scallop shell powder to calcium carbonate, the main raw material, produces almost no scattering of powder and is harmless to the human body.
Conventional dustless chalk was hard and sometimes damaged blackboards or broke into small pieces during use, but as a result of repeated research, the optimal ratio of scallop shell powder was found, and the chalk has evolved into a chalk that does not damage blackboards or break. Because of its density, it can be used twice as much as plaster chalk, and is now used in many schools.
Recensioni
Ancora non ci sono recensioni.