Although lithography was invented in 1798, it was at first too slow and expensive for poster production. Most posters were woodblocks or metal engravings with little color or design. This all changed with Cheret’s "three stone lithographic process," a breakthrough which allowed artists to achieve every color in the rainbow with as little as three stones - usually red, yellow and blue - printed in careful registration. Although lithography was invented in 1798, it was at first too slow and expensive for poster production. Most posters were woodblocks or metal engravings with little color or design. This all changed with Cheret’s "three stone lithographic process," a breakthrough which allowed artists to achieve every color in the rainbow with as little as three stones - usually red, yellow and blue - printed in careful registration. Although lithography was invented in 1798, it was at first too slow and expensive for poster production. Most posters were woodblocks or metal engravings with little color or design. This all changed with Cheret’s "three stone lithographic process," a breakthrough which allowed artists to achieve every color in the rainbow with as little as three stones - usually red, yellow and blue - printed in careful registration. Although lithography was invented in 1798, it was at first too slow and expensive for poster production. Most posters were woodblocks or metal engravings with little color or design. This all changed with Cheret’s "three stone lithographic process," a breakthrough which allowed artists to achieve every color in the rainbow with as little as three stones - usually red, yellow and blue - printed in careful registration.