If you have studio Japanese pottery or other handmade 20th century ceramic items at home, you may be pleased to hear that works of this nature tend to fetch at least £200 at auction and can be worth up to £12,000.

An auction of work by Japanese master potter Shoji Hamada (1894-1977) and Bernard Leach (1887-1979), who collaborated with Hamada and established the St Ives Pottery in Cornwall in 1920, is to take place on September 16th at Bonhams in London. The auction coincides with the exhibition, Shoji Hamada Master Potter, at Bonhams (September 4th-17th).

Mr Ben Williams, manager of the Futures Department at Bonhams, says that while readers are less likely to have works by the Japanese potters, Bernard Leach made more than 100,000 pieces over his working life "so there's every possibility that readers may have them".

Leach's work bears the initials BL. He varied his mark throughout his life, which helps valuers to date his work. BL is normally accompanied by the seal of the pottery at which the piece was made. If it was made at St Ives, it should show an "S" with a line crossing it horizontally with two dots in the empty quadrant.

Any piece by Leach should be worth at least £200 in good condition. The scale of the piece and a favourite design such as the "Pilgrim" (a hooded, medieval figure with a staff and bowl) can enhance values to as much as £12,000. A large stoneware plate featuring the "Pilgrim" design has an estimate of £8,000 to £12,000 sterling at the forthcoming auction.

Mr Williams estimates that a tall stoneware bottle vase by Shoji Hamada with a wax resist design of foliage to either side, from about 1930, should fetch between £7,000 and £9,000. Stoneware is a type of gritty clay fired at high temperatures which makes the body watertight (compared to earthenware, which is not watertight). Wax resist is a technique where wax is put on the body of the clay. Then the pottery is dipped into a glaze and the glaze runs off the waxed area, achieving a double layer of colour.

A stoneware cut-sided bulbous pot by Hamada with painted green and red enamel has an estimate of £6,000 to £8,000, while a similar price is expected for a stoneware square dish by Hamada in tenmoku (a Japanese glaze with a rusty, orangey-dark brown hue) with a vertical and wavy kaki (rusty) design.

If you have a ceramic object at home similar in shape to a goodsized tin of paint, you could be looking at ceramic handwarmers. These would have been used in a similar way to a charcoal brazier. A pair of these unusual items in the Bonhams sale is expected to fetch between £8,000 and £12,000. Hamada returned to Japan in 1924 to establish his own pottery and by 1955 he was designated a "Living National Treasure", a title awarded to craftsmen practicing applied arts like ceramics, textiles or lacquer-ware in the Japanese tradition.

Also included in the sale are items of a personal nature such as a scroll featuring a drawing entitled "The Road", showing a road disappearing into the distance, with an estimate of £2,000 to £3,000. At either end of the scroll are ceramic batton caps crafted by Leach and signed BL. The back is inscribed to his wife: "For Janet my wife, at my death".

Readers who would like Japanese pottery or other 20th century ceramic items valued are welcome to send a photograph with their name, phone number, the size of the piece and a description of any marks to Mr Ben Williams, Futures Department, Bonhams, Montpelier Street, Knightsbridge, London SW7 1HH.