A detection device for molten metal is provided. The detection device includes a sample cup having a cavity configured to receive a sample of molten metal and a blob arranged in the cavity. The blob includes a carbide stabilizing element and a hydrogen releasing material including a hydroxide of an alkaline earth metal. The blob is provided for use in detecting phase change temperatures during solidification of a sample of molten cast iron. The blob is also resistant to moisture gain and moisture loss during transport and storage. A method of detecting phase change temperatures of the molten iron or molten cast iron sample using the blob and a method of manufacturing the blob are also provided.