Colin is an engineer by training. He served a six-year apprenticeship, has a Master of Science degree, a Diploma in Engineering Management and is a Chartered Engineer. In 2002 he was elected a QinetiQ Fellow for his work on system engineering verification (have we built the thing right?) and validation (have we built the right thing?). In 2004 he founded his own specialist company which worked internationally for 10 years. Colin has recently completed his four-year term as president of the Association for the History of Glass and writes and lectures on a variety of glass-history topics, particularly the development of British Crystal glass in the sixty years 1642-1702. Colin and first wife Sue had three papers on this topic published in Glass Technology. Sadly Sue died of cancer in 2016 and did not live to see the last one in print. Colin’s second wife Sylvia, who was helping write the fourth paper, sadly died of motor neurone disease in February 2018.
This short paper was prepared as a tribute to the late David Martlew following his untimely death on June 6th. As many of you will know David masterminded the History and Heritage sessions at SGT annual conferences. The work reported here came out of a question I asked when presenting a paper at the September 2018 H&H day. I had noticed that a number of analyses of 17thC English and Irish lead-saltpetre glasses had low levels of sodium and/or chlorine. The amounts involved are close to typical XRF detection limits, but still stand out because these glasses have very few impurities in them. I asked if anyone knew why the glassmakers might have added a pinch of salt to some of the glasses. David was the only one to respond and suggested that salt acts as a wetting agent and hence facilitates better contact between sand grains and the alkali solution. I subsequently found two historic references to the use of salt in glass melting and Mark Taylor kindly agreed to do some trial melts for me, particularly to compare melting with and without 1.5% salt in the mix. The salt gave a significant improvement. David was delighted to see the pictures but was concerned that it would be hard to quantify the improvement. He scanned and edited part of his PhD thesis to give me a better idea of the theoretical background and suggested that we work this up to something we could share at a future H&H session. Sadly that was not to be, but David’s insight and support have been key to solving this problem and helping us appreciate how English and Irish glassmakers achieved the dramatic cost reductions that were essential to establishing the ‘Flint Glass’ brand as a world leader.