The headspace values in DT.11 were mainly based on BSI and British Glass and other standards, and on conclusions following many discussions and studies over the period 1986-1989 which eventually culminated in the new BS 7367 - Specification for the manufacture of glass bottles for carbonated soft drink bottles including carbonated water, in 1991). The latter made very similar recommendations to DT.11 but headspaces were slightly lower, as can be seen from the reference comparisons. The general background in the UK is that, around 1986, there were a series of TV and press/media reports usually involving Dr Willhoft, drawing attention to some individual cases of injuries caused by "exploding" bottles. The bottles involved were usually 1 litre sizes and the breakages were usually attributed to excessive design headspace by Dr Willhoft. He initially recommended zero headspace, but subsequently modified this to 1%. All other technical experts - and trade associations and the Glass Federation recommended 3.5% for litre bottles. They believed that the breakages were due to other factors and not excessive headspace. The consumer groups were not initially convinced until detailed studies had been made. The existing BS at the time - BS 6119 Part 1: 1981 - Glass bottles for carbonated soft drinks - recommended a design vacuity (headspace) of approximately 3.5%. Because of concerns, BSI set up a special safety panel to study headspace in particular, but eventually to produce a new standard (this was BS 7367 and was issued 4 years later in 1991). The Safety Panel had members drawn from BSI, consumer groups, the government (DTI) trade associations such as BSDA, brewers, retailers and the GMF. The government DTI member chaired the panel and BSI held the Secretariat. The writer was one of the glass representatives on the panel as also was Jimmy Knappe, who will be known to many CETIE members. The GMF engaged Brian Moody as the UK glass consultant to produce a Fact Sheet on headspace. During their work the panel collected relevant standards from within Europe and USA (listed in references). It also considered technical submissions and reports of work carried out from the glass and bottling federations as well as technical submissions from Dr Willhoft. While most carbonated soft drinks headspaces in Europe were within the values being discussed and specified in the UK, some were not. The WG members involved reported that these bottle designs were not giving problems and had food safety records and they saw no reason to redesign and lower their headspaces. After studying the evidence and the reports and standards made available to the WG a compromise was reached in DT.11. This allowed DT.11 to be produced and released in 1989. The compromise allowed those countries using larger headspaces to continue to do so for these existing bottles but to target slightly lower values for the future. It allowed those countries under pressure for lower headspace's (like the UK) to perform within the maximum values stated in DT.11 for non pasteurised bottles while still meeting their own national standards, which was a perquisite of their bottling and brewing customers. The Section B values in DT.11 are taken directly from Table 9 in TEC 7 for unpasteurised bottles. The Section A values in DT.11 are Section B values multiplied by 1.66 - the factor stated in TEC 7 for this purpose. This was the multiplication factor originally put forward by the bottlers as necessary for the additional expansion created during pasteurising. For the purposes of DT.11, however, Section B was re-titled as a "target" for "non-pasteurised bottles" and was intended to specify target values for new bottle designs. Section A was re-titled "Pasteurised, or non Pasteurised bottles" rather than just be related to pasteurised bottles as in TEC 7. It therefore accommodated existing pasteurised bottles and also those few existing European non-pasteurised bottles with headspaces larger than the Section B targets. The subject of design headspace was kept under review by the WG members up to the release of BS 7367 in 1991. No problems or adverse comments had been experienced so the matter was then deleted from WG 1 work programme. As far as the writer (John Lomax) is aware, the situation is still satisfactory and the recommendations still represent the best compromise design headspaces for carbonated soft drinks.
