Safe and good quality raw materials are essential to the consistent production of high-quality products. However, materials may be changed by suppliers without the knowledge of the manufacturer, either in order to reduce costs or because they are unable to accommodate changes in materials that have been
dictated by regulations. This kind of change is known as a "silent change" in Japan. Use of a non-standard raw material in a product means not only quality can no longer be assured, but has been known to cause accidents and is becoming a problem for society. Manufacturers can avoid these situations by checking at receipt whether the raw materials delivered are according to standard. In this article, we use samples that may have been subject to a "silent change" (hereafter called "silent change" product) and introduce case analyses that confirm such changes using energy dispersive X-ray fluorescence spectrometry (EDX) and FTIR infrared spectrophotometry.