The Rookwood Pottery Company of Cincinnati, Ohio, was started in 1867 and thrived for many years, closing its doors in 1967. Rookwood Pottery is popular with collectors because the pieces are classical in design and stand the test of time. Rookwood focused on creating art pottery as opposed to production pottery. Each piece of pottery is well marked, which helps to date it and estimate its value in the pottery collector's market. Learning the various ways to identify Rookwood Pottery takes time. Start out by going to antique shops, auctions and doing research online. Check books out of the library. The more Rookwood Pottery pieces you look at, the easier it'll become to recognize them, including judging their value based on quality, age and demand.
Watch for pieces made with the Rookwood Pottery's signature Standard glaze. The surface will have deep yellow, orange and red over a dark brown background. The entire piece of pottery was then coated with a high-gloss clear glaze. These are highly prized in the collector's market. Rookwood employed glaze chemists who created new glazes all the time but the most noted ones were the Standard and the matte and vellum glazes.
Look for glazed pieces that appear to be airbrushed. This technique was introduced into the pottery in 1884. The glaze technique was eventually patented by the pottery.
Check on the bottom for the famous Rookwood Pottery stamp. It consists of an "R" and "P" set back to back with the R facing to the left. This stamp was first used in 1886. Each year until 1900, a flame was added to the RP stamp. Count the flames in the stamp and add the number to 1886 to figure out what year it was made. Starting in 1901, an impressed Roman numeral was added under the Rookwood stamp to signify the year the piece was produced. For example, VIII indicates a piece was made in 1908.
Look for marks of well-known artisans that worked for Rookwood Pottery like Japanese-born Kataro Shiriyamadani. He worked for the pottery from 1894 to 1947 and is probably the most famous of all Rookwood artisans. These marks can be found in books written on the Rookwood Pottery such as "Warmen's Rookwood Pottery: Identification and Price Guide," by Denis Rago (2008).
Watch for letters impressed into the bottom of the ceramic piece, "O" for olive, "G" for ginger and "P"for soft porcelain. These stand for the clay body used to make the piece.
Examine the bottom of the ceramic piece for numbers and letters stamped into the clay. These refer to the shapes and glazes and quality of various pieces. Shapes were numbered 1 to 7301 and each had a letter designating the size of the shape: A, B, C, D, E and F. A was the largest size of any given shape, and F was the smallest. There were other letter designations, including "S" for special piece, "Z" for matte glaze, "V" for vellum glaze, "T" for trial (or experimental) piece and "X" for imperfect piece, which were usually sold as seconds and for less money.