or quicklime. Lime oxide, produced by cooking calcareous stone, a whitish, solid substance with an earthy quality. Mixed with water the lime expands, produces heat and becomes calcium hydroxide or slaked lime. Slaked lime is obtained by soaking lime in a quantity of water, equal to two and a half times its weight, and is the first material used in the preparation of a mortar . Through excessively shaking the slaked lime with water, a white liquid is obtained called milk of lime, which is used as a base for various methods of painting a secco. By purifying, drying, and pulverizing the slaked lime, lime white or Saint John's white is produced. Lime is distinguished in two types: fat lime and lean lime; the first is obtained by cooking limestone almost purely, while the second includes calcareous rock with magnesium or agrillaceous rock (less pure). Compared to the lean lime, the fat lime is more adapt to painting: fat lime slakes quickly, allowing for a greater volume of slaked lime and for a good take to the surface.