Cov tib neeg ntxov tshaj plaws tau pom tias charcoal tuaj yeem siv los pleev xim. Ntev ua ntej qhov kev tsim ntawm kev sau ntawv, tib neeg siv charcoal los pleev xim. Toner lossis charcoal murals tseem tuaj yeem pom hauv European qhov tsua.
Thaum Ntxov Nrab Hnub nyoog, tib neeg tau pib pom tias cov txiv qaub thiab dej tuaj yeem siv los ua thaiv - cov khoom zoo li tus, uas tuaj yeem sau rau ntawm qhov tsaus ntuj lossis tawv tawv siv txoj hauv kev zoo ib yam li cov cwj mem hluav taws xob. (Daim ntawv yog ib yam khoom kim heev nyob rau hnub ntawd, thiab nws yog ib qho yooj yim rau plooj nrog ib tug charcoal cwj mem carved rau ntawm ntoo thiab pob zeb).
Nws yog ib qho nyuaj rau kev txheeb xyuas leej twg thawj zaug xav txog lub tswv yim no, tab sis thaum ntxov, lub luag hauj lwm ntawm chalk yeej tsis siv rau kev qhia. Yuav kom siv dav hauv kev qhia, daim ntawv dub yog qhov tseem ceeb tshaj li daim kab dam.
Before the 19th century, black lacquer was used to coat wooden boards to protect them from erosion. It is also used to announce important matters, and compare the role of similar bulletin boards. But "blackboards" back then were small and not intended for teaching. But in the middle of the 19th century, universities all over the world began to flourish. The original teaching method of teacher dictation and student dictation became more and more inconvenient due to the increase in the number of students. Therefore, in Europe and the United States, the original teaching method began to be widely used. Small, non-stationary black bulletin boards have been enlarged for teaching purposes to facilitate remote students to copy the teacher's dictation.
Yog li ntawd, tom qab ze li ntawm ob puas xyoo ntawm kev hloov pauv qeeb, kev kawm, uas yog thawj zaug nyuaj heev rau kev nrov, thaum kawg tau hloov mus rau hauv cov cuab yeej yooj yim, tso cai rau ntau tus tub ntxhais kawm kom tau txais kev paub txaus los tshem tawm cov neeg tsis nyeem ntawv thiab tsis paub txog pej xeem. Muaj ob hom chalk siv nyob rau hauv Suav teb: zoo tib yam chalk thiab hmoov av -dawb chalk.
