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Materials engineering

Competitive ceramics

Partnering among industries in research center results in fewer losses and higher quality products

Eduardo CesarMugs, after drying, before firingEduardo Cesar

In the town of Pedreira, some 130 km away from São Paulo, the main shopping streets display in their shop windows a large range of decorative ceramic objects, such as colorful miniatures, plates, tumblers and penguins of various shapes and sizes, also known as earthenware. “Virtually the entire town lives from ceramics”, says professor Elson Longo, the coordinator of CMDMC, the Multidisciplinary Center for the Development of Ceramic Materials, one of FAPESP’s 11 Centers of Research, Innovation and Dissemination. For the last four years, this center has been involved in a partnering project with 29 companies in this town to help them manufacture better quality objects. “We started with raw material quality control”, says researcher Shirley Cosin, who was invited by CMDMC to coordinate the project in the town of Pedreira and who has worked in the ceramic industry for 28 years.

At the start of this process, for instance, the companies received clay with too much magnetic iron in it. “When the clay contains iron, the objects acquire black spots and get a defect in the middle of the piece that is called a black heart and only appears once the object has been fired”, explains Longo, from the Chemistry Institute of Paulista State University (Unesp) at Araraquara. To check whether the clay actually has iron residues it is necessary to conduct trials at Liec, the Interdisciplinary Laboratory of Electrochemistry and Ceramics at the Federal University of São Carlos (UFSCar), which is connected with CMDMC. “If some of the clay lots are not in line with the parameters set when the purchase was agreed, as verified through sampling, they are returned to the supplier”, says Shirley.

Another recurring problem was the size of the grains of quartz and of feldspar, raw materials that, together with clay and kaolin, make up the basic mixture that is used to make ceramic objects. The suppliers never respected the grain size stipulated by the industries. “Instead of smaller grains, technically called 200 mesh, 80 mesh was delivered”, Shirley tells us. This caused serious problems, because the larger particles caused defects in the ceramic pieces. “Ever since we instituted control of the incoming raw material at the companies, there has been a vast improvement”, says Shirley. “Before, the clay that was delivered was totally gray whereas today what arrives is white and more suitable for making artistic ceramic pieces.”

All the clay used in Pedreira is purchased from a single supplier in the town of São Simão, also in inner-state São Paulo, where it is extracted from riverside areas. “Here we encounter a major problem: the product’s poor quality, as its composition includes 30% moisture, 20% peat and 10% to 15% sand”, says Longo. In other words, only 40% of the raw material purchased for R$500.00 to R$600.00 a metric ton is actually usable. To move up to another level of quality calls for suitable extraction and processing techniques, which take time, so that researchers came up with an alternative. They suggested to the companies that they purchase clay imported from England, which was already being used by other firms in Brazil, with the same price as the domestic product. “The advantage of the imported raw material is its quality, which reduces the production process stages”, says Shirley. “One doesn’t have to grind or to wash the clay; it can be weighed and chucked right into the mill.”

Eduardo CesarPorcelain pieces are decorated with golden linesEduardo Cesar

Savings in the firing
As the clay is pure, there are also gains in the firing process. “Firing, which used to be conducted between 1,280 and 1,320 degrees Celsius, depending on the amount of quartz in the clay, is now carried out at a constant temperature of 1,200 degrees”, says Shirley. Lowering the temperature by some 80 degrees provides significant process cost savings. The lower temperature also means objects with fewer retractions and consequently fewer defects.

At first, the industries were shy about importing clay, but little by little, they converted. “After the pilot tests conducted with at least 16 companies, a large order was placed”, says Shirley. The director and proprietor of the company Porcelanas Lu, Valdemir Pansani, tells us that with the support of the project he was able to cut losses from 40% to 10%. “This project appeared at the right time, because I was having a lot of difficulties and the company was in serious risk of closing down”, says Pansani. Ever since the firm started screening the incoming material, losses were cut. “The work of monitoring and controlling the clay mixture and the glaze improved the quality of the product substantially and, as a result, I became more competitive.”

Uninterrupted work
The company, established in 1986, has 80 employees who take turns performing the several functions 24 hours a day. One of the main Porcelanas Lu products are the penguins, of which the firm has 70 different models, ranging from the traditional kind to those rigged out as chefs, musicians and families. The company also manufactures miniatures, mugs with corporate logos, sets of cups, vases and decorative plates. The aim of the enterprise’s owner, who also has two stores selling his products in the town, is to cut losses to about 5%.

After firing, the pieces are decorated with transfers or silk-screened. These processes are also closely monitored by the researchers. “One of the pigments used to print designs on the pieces was generating a series of defects”, Shirley tells us. The pigment was purchased as having microscopic particles, but they were actually larger. “We started controlling the size of the particles and solved the problem”, she says. Recently, one of the factories started having problems with its mug handles, 80 percent of them coming unstuck after gluing, a process conducted manually. “This was happening because the mixture was not homogeneous”, she tells us. In other words, the process of making the glue with the right viscosity was not being strictly followed.

The idea of working in collaboration with the ceramic center was the brainchild of Mayor Hamilton Bernardes Junior, who decided to propose the partnering arrangement after he learnt about a similar project conducted with the ceramics manufacturers in the town of Porto Ferreira. Besides the project’s 29 participants, hundreds of other small and tiny firms in the ceramics sector also benefited from the exchange of knowledge. According to those who were involved with the project, this partnering has no end date, because the technical know-how transferred to the companies must be constantly reassessed. “Even with the technical advances achieved four years after the agreement with the city council was first signed, there is still a lot to be done”, says Longo. This year, the town council approved funding totaling R$70 thousand for the project. One of the ideas that is brewing is to create a cooperative to produce the ceramic mixture comprised of clay and the other ingredients, which would lead to industrial process gains. “With the establishment of central production, the businessmen would no longer have to worry about raw material quality”, says Longo.

The project
Multidisciplinary Center for the Development of Ceramic Materials (nº 98/14324-0); Type Cepid (Innovation, Research and Dissemination Center); Coordinator Elson Longo – Unesp; Investment R$ 1 million a year (FAPESP)