A Question of Colour
12 January 2007
UK glass recycling in the UK continues to be constrained by the colour imbalance, but a report recently published by WRAP (Waste & Resources Action Programme) will help the industry to absorb more green glass in its current production.
The two-year Colourite project, carried out for WRAP by Glass Technology Services Ltd (GTS) in close co-operation with container glass manufacturers, explored the technical and aesthetic barriers to increasing the amount of recovered glass (cullet) from mixed colour collections that can be used in the production of new clear glass containers.
The project objective was not to counteract the growing level of mixed colour collected glass, but to highlight the affects that higher levels of mixed colour collection will have on clear glass colour quality in the future.
“In simple terms, the UK container industry has a large unsatisfied demand for clear cullet but an oversupply of green cullet. This imbalance is being exacerbated by the growing trend towards mixed colour collections, which results in higher levels of colour contamination and the additional loss of clear cullet during the sorting process,” explains WRAP’s Glass Technology Manager, Andy Dawe.
“In commissioning this project, we took a pragmatic view that these issues are here to stay and the aim of the project was to find ways to maximise the amount of cullet that container manufacturers can use in their furnaces from these sources. We approached the problem from both ends of the quality spectrum; how good a glass can be made and how good does the glass have to be to satisfy brand owners, packaging designers and the consumer.”
The first phase of the project focused on technical solutions to allow clear glass furnaces to produce an acceptable product using colour-contaminated cullet. Culminating in full scale manufacturing trials, this work has established that an acceptable quality can be achieved cost effectively by adding commercially available decolourisers to the furnace.
To help container manufacturers to adopt this solution, the team developed a robust but simple sampling method for measuring the degree of colour contamination in the cullet and a user-friendly model to predict the effects of adding the decolourisers to already complex batch ‘recipes’. The Excel-based programme quickly guides busy furnace managers through the procedure, and is already being used by the industry.
Another important result of the work has been the development of a specification for colour contamination of processed glass which makes use of the new sampling method and has been agreed by both the glass processors and the container manufacturers.
“Fundamental to the success of this project was active engagement of all elements of the supply chain from the waste glass collectors to the major retailers. Having established this level of co-operation, the project team were then well placed to address the complex issues which influence cullet use including technical aspects of the colour contamination of processed cullet in the production of clear container glass and marketing issues, such as the possible affect on the consumer buying decision should the colour of clear glass become slightly green.
“Of particular value to the glass manufacturers was the development of a colour predictive model which has given them the opportunity to predict the colour implications of cullet additions to their products. It is anticipated that the model will give the glass manufacturers the confidence to maximise their cullet additions and its widespread adoption by the glass industry will greatly assist the recycling opportunity for recovered glass,” says Dr Nick Kirk, GTS’ Research Manager.
Tackling the issues from the end customer perspective, the second phase of the project explored the impact that using various shades of glass (clear versus shades of green) for food and drink containers has on consumer perception and attitudes.
Conducted by the Psychology of Design group at the University of Leeds, the research has shown that, in many cases, the colour and clarity criteria adopted by glass manufacturers, brand owners, and marketeers are much more stringent than those required by the consumer.
“Alongside the technical challenges, this over-engineering of the product has limited the opportunities to increase the use of mixed recycled glass and we hope the results will be of interest to the industry and its customers in the future when decisions about glass container colour and clarity are made,” says Andy Dawe.
The Colourite project complements other work being carried out by WRAP to address the UK’s glass colour imbalance, including new guidance for designers on specifying recycled content in glass packaging, and a project to encourage bulk importing of wine and bottling in lighter green bottles manufactured in the UK.
The full report is available in PDF format on the WRAP website at www.wrap.org.uk.
The two-year Colourite project, carried out for WRAP by Glass Technology Services Ltd (GTS) in close co-operation with container glass manufacturers, explored the technical and aesthetic barriers to increasing the amount of recovered glass (cullet) from mixed colour collections that can be used in the production of new clear glass containers.
The project objective was not to counteract the growing level of mixed colour collected glass, but to highlight the affects that higher levels of mixed colour collection will have on clear glass colour quality in the future.
“In simple terms, the UK container industry has a large unsatisfied demand for clear cullet but an oversupply of green cullet. This imbalance is being exacerbated by the growing trend towards mixed colour collections, which results in higher levels of colour contamination and the additional loss of clear cullet during the sorting process,” explains WRAP’s Glass Technology Manager, Andy Dawe.
“In commissioning this project, we took a pragmatic view that these issues are here to stay and the aim of the project was to find ways to maximise the amount of cullet that container manufacturers can use in their furnaces from these sources. We approached the problem from both ends of the quality spectrum; how good a glass can be made and how good does the glass have to be to satisfy brand owners, packaging designers and the consumer.”
The first phase of the project focused on technical solutions to allow clear glass furnaces to produce an acceptable product using colour-contaminated cullet. Culminating in full scale manufacturing trials, this work has established that an acceptable quality can be achieved cost effectively by adding commercially available decolourisers to the furnace.
To help container manufacturers to adopt this solution, the team developed a robust but simple sampling method for measuring the degree of colour contamination in the cullet and a user-friendly model to predict the effects of adding the decolourisers to already complex batch ‘recipes’. The Excel-based programme quickly guides busy furnace managers through the procedure, and is already being used by the industry.
Another important result of the work has been the development of a specification for colour contamination of processed glass which makes use of the new sampling method and has been agreed by both the glass processors and the container manufacturers.
“Fundamental to the success of this project was active engagement of all elements of the supply chain from the waste glass collectors to the major retailers. Having established this level of co-operation, the project team were then well placed to address the complex issues which influence cullet use including technical aspects of the colour contamination of processed cullet in the production of clear container glass and marketing issues, such as the possible affect on the consumer buying decision should the colour of clear glass become slightly green.
“Of particular value to the glass manufacturers was the development of a colour predictive model which has given them the opportunity to predict the colour implications of cullet additions to their products. It is anticipated that the model will give the glass manufacturers the confidence to maximise their cullet additions and its widespread adoption by the glass industry will greatly assist the recycling opportunity for recovered glass,” says Dr Nick Kirk, GTS’ Research Manager.
Tackling the issues from the end customer perspective, the second phase of the project explored the impact that using various shades of glass (clear versus shades of green) for food and drink containers has on consumer perception and attitudes.
Conducted by the Psychology of Design group at the University of Leeds, the research has shown that, in many cases, the colour and clarity criteria adopted by glass manufacturers, brand owners, and marketeers are much more stringent than those required by the consumer.
“Alongside the technical challenges, this over-engineering of the product has limited the opportunities to increase the use of mixed recycled glass and we hope the results will be of interest to the industry and its customers in the future when decisions about glass container colour and clarity are made,” says Andy Dawe.
The Colourite project complements other work being carried out by WRAP to address the UK’s glass colour imbalance, including new guidance for designers on specifying recycled content in glass packaging, and a project to encourage bulk importing of wine and bottling in lighter green bottles manufactured in the UK.
The full report is available in PDF format on the WRAP website at www.wrap.org.uk.
Editor's notes:
- WRAP works in partnership to encourage and enable businesses and consumers to be more efficient in their use of materials and recycle more things more often. This helps to minimise landfill, reduce carbon emissions and improve our environment.
- Established as a not-for-profit company in 2000, WRAP is backed by substantial Government funding from Defra and the devolved administrations in Scotland, Wales and Northern Ireland.
- Working in seven key areas (Construction, Retail, Manufacturing, Organics, Business Growth, Behavioural Change, and Local Authority Support), WRAP’s work focuses on market development and support to drive forward recycling and materials resource efficiency within these sectors, as well as wider communications and awareness activities including the multi-media national Recycle Now campaign for England.
- More information on all of WRAP’s programmes can be found at www.wrap.org.uk
Press Office
Media Relations Manager
WRAP
Tel: 01295 819928
press.office@wrap.org.uk
Andy Dawe
Glass Technology Manager
WRAP
Tel: 01295 819910
andy.dawe@wrap.org.uk
