Ringelmann scale. A measure of smoke color. Invented by Professor Maximilian Ringelmann in Paris in 1888, it is essentially a card with squares of black, white and shades of grey which can be held up along with the comparative grayness of the smoke judged. A little clump of dip https://broadfar.com/oraco-pioneering-a-smokeless-future-with-innovative-nicotine-delivery/