By George Kessler
The worst mystery I had to solve was about 35 years ago. I was running a factory in the east end of London whose processes included injection molding from 30 tonne to 400 tonne.
That department processed a wide variety of materials including clear polystyrene and clear acrylic (which was costly then).
We had got our overall reject level down to under 2.5 percent including set up - which was not bad in those days for a short run operation. However we started to get sporadic discoloration in the clear acrylic moldings mainly from the afternoon on, and especially the night shifts (where we lost up to two hours production as scrap.
In those days the majority of machines were not digitally set so there was limited opportunity for machine process control (remember micro switches and valves which you turned). However our machines were well maintained and pretty consistent. We introduced some quite expensive monitoring and still found no reason why the machines should vary. In addition we invested in moisture measurement equipment (acrylic is hydroscopic) to check drying - still no success.
We called the material manufacturer in to analyze what was obviously (by process of deduction) faulty material and their analysis produced no result although they gave us a free tonne as a gesture of goodwill.
Finally I brought in a sleeping bag and stayed several nights at the factory getting up every hour to look at what was going on. I realized what the problem was when the very nice night shift foreman gave me a chapatti - I was starving. The mainly Bangladeshi workforce brought in food made by their family and heated it up in the powder dryers - occasionally the curry boiled and went over the edge of the little metal container that their spouses used.
The contamination that we had been seeing was curry. We bought a little (Belling if I remember) electric oven and solved the issue
George Kessler is a CBE. He is the Joint Deputy Chairman at Kesslers International Ltd in Stratford, London