Ceramic cups are ideal for coffee or tea and can be simple or customised. Ceramic mugs are made using a potter's wheel, the hand-building technique or through slip casting in moulds. Hand-building and making mugs on a potter's wheel are time-consuming and not as practical as slip casting, because the mugs that result have different sizes and even shapes. The industrial process used to make ceramic cups is through slip casting in moulds.
The first stage in the industrial process of making ceramic cups is to create a prototype in plaster or plastic. Plastic is more recommended, because it won't be destroyed when casting the moulds. Plaster moulds are destroyed while casting several sets of moulds. The prototype may be hand-built or carved into a block of material. The prototype contains all the details and looks like the final product.
Plaster moulds are necessary to be able to replicate the ceramic cups. Several moulds are prepared so that multiple cups can be cast at the same time and increase productivity. The moulds are cast after the prototype and contain several parts, typically two halves for the body of the cup and additional two halves for the handles.
The Slip Casting
Ceramic cups are manufactured using porcelain, earthenware or stoneware. The material is diluted using water until the clay becomes liquid. The clay is cast into the plaster moulds. Filling a mould with clay takes under one minute. The clay is left to harden and the plaster mould absorbs the moisture from the material. When the clay hardens, the moulds are removed.
The Firing of Cups
The firing of the ceramic cups is scheduled after the clay is completely dry. Hundreds of cups can be fired in a large kiln, which contains several shelves. The firing temperature depends on the clay used to make the mugs: porcelain requires temperatures up to 1,426 degrees C, while earthenware requires temperatures below 1,148 degrees C. The firing time is between two and 12 hours, depending on the type and size of the kiln. Immediately after the firing is finished, the cups are extremely hot, so they can only be removed a few hours after that using thick gloves.
The Glazing and Second Firing
The final stage in the making of ceramic mugs is the glazing, which is performed when the cups are no longer warm. Glazes add colour and a glossy texture to the cups; the cups may have an even colour or patterns and drawings. After applying the glazes, the cups will be fired again. The firing temperatures depend on the types of glazes and the initial material used for making the mugs.