I worked for GR Stein in the late 1970's and spent some time at Hipperholme. At that time the bricks being made were Selfrac insulating bricks based on ball clay and using a mixture of polystyrene beads and sawdust to provide the porosity.
When the bricks had been dried they were hand set into the kilns and firing started. Can't remember what temperature it was, but when the kiln reached a few hundred degrees (4 or 500 degree C?) the polystyrene & sawdust caught fire ( we called it "struck") and the gas supply could be turned off. The burning rate of the polystyrene/sawdust was controlled by means of dampers and the smelly products of combustion went into the flue system where there was a secondary burner that enabled the gasses to be burnt further and then released to atmosphere. When the kiln reached 700 or so degrees the main burners were turned on again and normal firing resumed.
The bricks themselves were made by a pug and repress process, and somewhat oversize - therefore they has to be ground to shape and size before despatch
Selfrac 23, 26 and 28 were the grades we made. The 23, 26 and 28 are abbreviations for the service temperature in hundreds of degrees Fahrenheit (2300F = 1260C)
Just before I left Allens we started to develop another insulation brick that was based on ball clay but using only sawdust to provide the porosity. It was less polluting & easier to fire and also cut out the repress stage of making, being only extruded & wire cut to size.
As far as I'm aware the site closed in the early 1980's, just after I left the employment of GR Stein
It's been good to have a wander round the old site.
Thanks.
