Why does the tint (color) of quicklime vary?
This is because of the different fuels used to heat the limestone (calcium carbonate) to convert it to quicklime (calcium oxide). Many suppliers use pulverized coal and a mixture of pet coke which can result in a slight grayish color to the quicklime due to the exposure to the fuel. You’ll notice that a pebble of quicklime, when split, will appear white inside since this area has not been exposed to the burning fuel directly. Generally, The tint of the quicklime has no significant bearing upon the reaction of the quicklime with water. This is because the amount of material associated with the color is insignificant. The exception would be if the quicklime were “overburned”, which could decrease the reactivity.
