Canning and Fish Packaging Technology

Unit 14 - Glass containers and Closures

14.1.4.Colouring compounds

• Amber colour: (Brown bottles of Laboratory) reagents Light yellowish to deep reddish brown. The colours usually obtained by adding various amounts of carbon and sulpher or iron and manganese oxide to the raw material.
• Blue: Glasses of various shades of blue can be made by adding cobalt oxide or less commonly copper oxide.
• Green: Obtained by the addition of iron, manganese and chromium oxides.
• Ruby glass: has colour which may range from orange red to deep shades. The colourants added are selenium and cadmium sulphide.
• Opal: An opaque or milky glass which is usually white (but can also be coloured) by addition of fluorides and alumina.