materials & components Glass materials & components

objectives Describe the aesthetic, functional and mechanical properties of glass Explain the reasons for selecting glass for commercial packaging Understand the automatic processes for mass-producing glass containers

Glass in commercial packaging Cost effective when mass-produced Resistant to mechanical shock as it strong when annealed Transparent offering excellent product visibility An inert material, so it is safe and will not react with the contents Relatively lightweight – today’s glass containers are more than 40% lighter than they were 20 years ago Reusable and recyclable Glass is one of the earliest materials used for containing food and drink and continues to be sued for a range of packages from jam jars to expensive perfume bottles. Glass has many properties that make an ideal for use as packaging material

Glass in commercial packaging In addition: It doesn’t deteriorate, corrode, stain or fade so the contents remain fresh Its contents can be preserved through high-temperature processing such as sterilisation of milk It can be sealed air-tight, to protect the contents from contamination and bacteria Glass is one of the earliest materials used for containing food and drink and continues to be sued for a range of packages from jam jars to expensive perfume bottles. Glass has many properties that make an ideal for use as packaging material

Glass & the environment 100% recyclable – it can be recycled endlessly with no loss of quality or purity, so recovered glass containers can be made directly into new glass bottles Recycling glass saves raw materials – for every ton of glass recycled a ton of natural resources is conserved Recycling lessens the demand for energy – energy costs drop when recovered glass is used in conjunction with virgin raw materials Recycling cuts CO2 emissions – for every 6 tons of recycled container glass used, 1 ton less of carbon dioxide is created No processing by-products – glass recycling is a closed loop system creating no additional waste or by-products

Colour In its purist form glass has a greenish tint. By adding chemicals to the raw mixture (sand, soda & limestone) different colours can be produced This is useful when designing glass containers for particular products i.e. beer is usually packaged in green or brown glass to protect it from direct sunlight

Glass versus polymers Glass has one major advantage over polymers: it has a more sophisticated image It gives a look of quality Disadvantage: It can shatter

Mass-producing glass containers Melting basic raw materials for making glass are quartz sand, limestone and soda ash, plus some oxides that act as catalysts to melt the glass. These are automatically mixed and fed into a furnace where they are heated up to 16000c to produce molten glass Shaping and forming Molten glass is fed into machines where it is automatically blown using either the blow-and-blow process for bottles or the press-and-blow process for wide-mouthed containers

Blow and blow process

Press and blow process

Annealing The hot glass containers undergo a slow and controlled cooling process to relieve internal stresses and make the glass stronger. Glass that has not been annealed is liable to crack or shatter easily when subjected to small changes in temperature or mechanical shock, such as been dropped Quality control inspection Once cooled the glass containers are channelled through inspection stations and are checked for dimensional accuracy , and body and neck quality. Inspection can be manual, semi-automatic or automatic

Packing After the inspection stations, the glass containers are put onto pallets and protected with shrink-wrap, ensuring safe delivery to customers

Support activity In your exercise books discuss why glass is used to package: Perfumes and aftershave? More expensive brands of sparkling mineral water? Explain your answers.

Exam question Explain two advantages of using PET bottles rather than glass bottles for the consumer (4 marks)

Exam question - answer PET does not smash like glass if you drop it (1) Therefore it is safer to use (1) PET is lighter than glass (1) Therefore easier for the consumer to carry it than a glass bottle (1)

EXAM ZONE You need to know: Properties of glass (aesthetic, functional & mechanical) Advantages and disadvantages Uses and applications