Unit 4 - Glass Bottles and Associated Packaging Flashcards
What does the design of a bottle need to consider?
It’s life cycle, from manufacturer, transit, filling labelling and packaging, storage, distribution and when its at the hands of a customer/consumer.
Why are exact dimensions vital?
As bottles may be filled to a level counterpressure / vent tube fillers. Variations can cause packages to be short or overfilled.
Describe glass.
Glass is an inorganic substance fused at a high temperature and cooled so it solidifies in a vitreous or non - crystalline condition.
All commercial glass is based on “Silica” which is the principle compound of sand.
Can beach sand be used to create glass?
It is unsuitable for making glass since it contains impurities and caries widely in composition.
Costs of furnace?
£25M and with an expected life of 10-15yrs.
Melting temp of around 1500C and continuous operation of 365 days a year.
Why is (Silica) mixed with other materials?
In order to lower the temperature and allow the glass to melt, mix well and release any air.
What is a typical mix or “batch”?
Silica = 70%
Soda Ash = 15%
Limestone = 9%
Refining Agents
Colourants
De- colourisers =6%
Why would cullet glass normally be added?
at the rate 30-75% and this reduces the temperature required for the melt to below 1500C, saving up to 10% of the energy consumed.
What creates an Amber colour?
Amber - Iron, sulphur, carbon
What are the 3 main processes for the production of glass containers?
- Blow and Blow
- Press and Blow
- NNPB (Narrow Neck Press and Blow)
Describe the Bottle Forming Process.
Bottle forming is essentially a two stage process. The blank side receives the “gob” and makes the “blank” or “parison”. this partly formed bottle is then transferred to the mould side and the parison is blown into the final shape.
Describe the Blow and Blow process.
Beverage glass bottles up until the 70’s were made using this process. The gob is dropped into the black mould, then two puffs of compressed air are successively applied to each end of the blank. The parison is then transferred into the final mould and is blown to shape.
Describe the press and blow process.
With this process, the parison is not made by blowing but by being pressed into an exact shape by a plunger. This makes the process especially suitable for glass jars.
Describe the NNPB process.
This is a modern process which allows bottles which would normally have been made using the blow and blow method, to be light weighted by 10% to 20%, due to a consistent wall thickness. This process is not available for heavy bottles.
A high degree of precision is required with this technology and it’s normal for manufacturers to only be interested in using this process when there is a large volume to be produced, tooling cost is also higher.
Why do they anneal a bottle?
When the bottle leaves the forming machine its outer surface is hard having cooled to 300C, however the inner part is still hot and soft. If cooling was to continue naturally, the inner parts would would contract more than the outer cooler surface and dangerous stresses would develop.
If a bottle is left to cool annealing, it is so weak that if you give a tap with something metallic, it will implode. Annealing is therefore necessary and involves heating the bottle to 550C and then slowly cooling it down in a tunnel called lehr.
