Dust-free chalk is not a health hazard, so why do you still see white dusty foam?

Chalk is a widely used tool in everyday life, generally used for writing on blackboards. In ancient times, chalk was usually made from natural chalk, but nowadays it is mostly replaced by other substances. The main component of chalk is calcium sulfate, a white precipitate that is not easily decomposed and has particles larger than dust. Domestic use of chalk mainly ordinary chalk and dust-free chalk two kinds, its main ingredients are calcium carbonate (limestone) and calcium sulfate (gypsum), or contain a small amount of calcium oxide.

Dust-free chalk is only in the ordinary chalk to add grease or polyalcohol substances as a binder, and then add a larger specific gravity of the filler, such as clay, marl, cement and so on so that the specific gravity of the chalk dust and the volume of the dust are increased, not easy to fly apart. But "not easy to fly apart" is not completely do not fly apart, so the so-called "dust-free chalk" should be called "dust chalk" more appropriate.

Together with some of the dust-free chalk production process and the use of raw materials is not necessarily strict control, so in practice, it is not very obvious to reduce the effect of chalk dust pollution. In response to such shortcomings, many teaching institutions began to use whiteboards and whiteboard pens, completely avoiding the impact of dust. Whiteboard pen is mainly made of pigments and solvents, generally use alcohol as a solvent, but also some bad quality using acetone, ethylene glycol, xylene and other toxic substances as a solvent, there will be a pungent odor, affecting health.

Because alcohol is volatile, the use of alcohol made of whiteboard pens if you do not cover the pen cap, the pen is very easy to dry and lost, which is also a major drawback. A new generation of water-soluble dust-free chalk, similar in appearance to ordinary chalk, using titanium dioxide and vegetable oils and fats and other components. In the writing and wiping process 100% dust-free, water can be dissolved, without changing the existing blackboard, but also to avoid the traditional chalk alkaline dust on the corrosion of electronic teaching equipment.