Listed below are answers to Frequently Asked Questions resulting from visits to the GLASSFOREVER Education Centre.

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Q: Where does Rockware's used glass come from?
A: Rockware's used glass is collected from all over the UK.


Q: How many bottle banks are there in the UK?
A: Approximately 23,000.


Q: Where do you put different coloured glass eg red/yellow?
A: In the green bottle bank.


Q: How are bottle banks emptied?
A: Cranes lift up the bottle banks and pull a lever at the top of the bank which opens a door underneath so the glass is released.


Q: How often are bottle banks emptied?
A: This depends on the contract with the waste collection company eg Berryman (3 times a week etc).


Q: How could we set up bottle bank schemes within schools?
A: Get in touch with your Local Council who will have their own waste collector.


Q: How is glass tipped off the special lorries?
A: These lorries have 3 compartments and the different coloured glass is tipped off separately as each compartment door is opened.


Q: How much do lorries cost?
A: The specialised lorries with 3 separate compartments cost around £70,000.


Q: How many tonnes of glass arrive at Reuse each day?
A: About 600 tonnes which is equivalent to 20 lorries.


Q: How much is used glass worth per tonne?
A: Approximately £25-£30.


Q: How many people work at Reuse?
A: About 32 staff and the plant runs 24 hours a day.


Q: From where are raw materials sourced?
A: Sand-Norfolk, Limestone-Derbyshire, Soda Ash (man-made)-Cheshire.


Q: How much glass went to landfill in the year 2000?
A: The UK uses approximately 2.2 million tonnes of glass per year. In 2000 35% of the UK's glass was recycled, unfortunately the remaining 65% went to landfill. This highlights the reason why Rockware is working hard to change peoples behaviour when disposing of used glass.


Q: How much glass is made at Knottingley?
A: 5-600 tonnes per day.


Q: Can sheet glass (window glass) be used in the bottle making process?
A: Yes, Rockware use some sheet glass (from other glass manufacturers) in the process but want to discourage the general public from putting window glass in bottle banks for health and safety reasons.


Q: How much cullet would be needed to make 1 tonne of recycled glass?
A: 1 tonne of cullet produces 1 tonne of recycled glass. However, 1.2 tonnes of raw material is required to produce one tonne of new glass.


Q: How much energy are we saving by using recycled glass?
A: Up to 18% of the energy required to make new glass is saved by using recycled glass.


Q: What sort of emissions are released in the glass making process and does using recycled glass cut down on emissions?
A: Nitrogen oxide, sulphur oxide and carbon dioxide are released when raw materials are melted in the furnace. However, when re-melting cullet to make recycled glass no further emissions are produced.


Q: Why is the recycling rate so low compared to other European countries?
A: Other European countries have been collecting waste glass much longer and have a long history of promoting recycling.


Q: Which is the hardest unwanted material to get rid of?
A: Ceramic (Pyrex) because it doesn't look that much different to glass but it melts at a different temperature to glass.


Q: How is Pyrex etc removed?
A: Pyrex is removed by hand in the picking station. If small pieces of Pyrex get through to the furnace problems occur. If any bottles and jars are contaminated with Pyrex they will be spotted by quality control and rejected.


Q: How are ceramics removed once they are detected by lasers?
A: A jet of air blows the ceramic out of the way.


Q: Are electromagnetic fields used to detect non-ferrous metals?
A: Yes, then a jet of air blows the metal out of the way.


Q: Where does any reject glass go?
A: It will go through the whole process again but any rejected material then goes to landfill at Copley Lane Quarry, Sherburn in Elmet (approx. 5 miles from Knottingley).


Q: Where does rejected glass from the manufacturing plant go?
A: This rejected glass gets crushed down and goes back into the furnace.


Q: How many unwanted materials are left in the cullet as it leaves the Reuse factory?
A: The glass collected from bottle banks can contain between 25-40% of unwanted material. After it has been through the Reuse process it is 99.99975% pure glass.


Q: How often do they change the moulds?
A: The moulds are changed whenever a container shape changes. It takes about 4 hours to do a mould change.


Q: What are the moulds made from?
A: Cast iron or, if it's a high volume job, aluminium bronze because it is very hardwearing and lasts much longer.


Q: How long does the glass stay in the lehr for?
A: Between 20-40 minutes.


Q: What is used to cool the bottles in the lehr?
A: Fans circulate air through the lehr and the warm air loses its heat through heat exchangers.


Q: Where did most of the technology come from in the Reuse plant?
A: The technology and working practices come from Australia where Reuse operate six similar plants. The machinery for this plant was imported from Germany.


Q: How much did the Reuse plant cost to build?
A: £4.5 million.


Q: Do furnaces operate on one colour of glass only?
A: Normally yes, but the colour can be changed by changing the raw materials. When this is done it takes two days for the new colour to go through the furnace.


Q: How do you colour glass?
A: Depending on the iron content in the sand the glass may have a greenish appearance. Special coloured glass can be created by adding small quantities of cobalt to make blue or chromium/iron to make dark green.


Q: Does different coloured glass weigh different amounts?
A: No, but they cost different amounts. For example, clear glass is the most expensive because it needs to have a lower contamination rate than green glass.


Q: Can recycled glass be used to make blue glass or are raw materials needed?
A: Yes, blue glass can be made by adding cobalt to clear glass. However, when blue glass is recycled it is added to the green furnace to make green glass.


Q: What colour of glass is made at Knottingley?
A: The Knottingley plant makes mainly beer bottles in green and amber, Doncaster uses clear glass to make food jars, Irvine (Scotland) make spirit bottles in clear and green glass. Worksop is a back-up plant for other clear glass orders.