Bitumen has been an important raw material for Evode. It is the waste product which remains when crude oil has been processed to produce oils and petroleum fuels. Chemically it is virtually identical with natural asphalt which occurs naturally in Trinidad Lake Asphalt and even the exudations in the Tar Tunnel at the Ironbridge Gorge. Since it was largely a waste product it was cheap. As Barry Jackson commented what other polymer costs only £20 a ton and can be made in to useful products to sell at £100 per ton. It exists in three main forms. The unmodified bitumen is fairly soft and sticky. This can be modified by blowing air through it to make oxidised bitumen which is more polymer-like. Then there are the very hard grades which are good for paints. Bitumen can be used in solid products which can be hot poured or used in extruded form. Bitumen will dissolve in many solvents and can be used in solution form. This is very useful for paints and similar surface coatings. Alternatively bitumen can be dispersed in water to make emulsions. These are frequently used for water proofing compositions for damp courses and roof water proofing. All these techniques have been employed in products made at Glover Street and Common Road. Dr Simon brought the original formulations for bitumen products from Germany.

The first order that he got in Britain was from a Builders Merchant, Walter Tipper in Uttoxeter for five gallons of a bitumen solution. He got the order, went back to Stafford and made it, then back to Uttoxeter to deliver it, all in the same day.

Some of the other earliest products were the 505 series of bitumen based paints. These were used for water-proofing basements and water holding tanks in World War II. Later an aluminium pigmented version called Silverfilm was designed by Cyril Lawton as a reflective finish for roofs. This was widely recognised as the leader in its field. A major contributor to profits was the application of roof waterproofing based on embedding hessian in to layers of bitumen emulsion. The bitumen emulsions were initially bought in but the decision was made to produce them. The first emulsions have been attributed to 1951 with production by Ted Wojtulewitz. In 1953 Barry Jackson was engaged with his first project to finalise the methods of production for bitumen emulsions. [Much useful detail about the development of bitumen products has been taken from the book by Barry S Jackson, "Sid Jackson's Son. The Life and Times of a Black Country Scientist," published by B S Jackson, 2000.] Barry made a theoretical study of the amount of surface active agent required to produce a stable emulsion only to find that Elias Peak, the works manager, had arrived at the same figure. The following is a quote from B S Jackson's book: 'He (Elias Peak) had arrived at my answer empirically. "Don't worry about it" he said "By using a bit of theory you've got as far in one day as I did in several months of experiment". I carried on with this simple soap model to find out the other chemical conditions that were needed for stability and then began to work this basic information up to the point where a useful product resulted.'

Bitumen was bought in 3 cwt drums and had to be broken by hand and fed in to a coal fired road tar boiler. In summer the bitumen softened and was very difficult to break up. It was found that by starting at 5 am the work could be completed in about twenty minutes whereas later in the day this could take up to five hours. The molten bitumen was run by gravity to a Hurrell emulsifier and water in which emulsifying chemicals had been added also fed to the emulsifier. About three tons of bitumen and 2 tons of water made 5 tons of emulsion. The force of the Hurrell was used to pump the product in to a storage tank.

The product being water based corroded the steel drums. Dr Jackson introduced the concept of using sodium bichromate to prevent this so that product could be stock­piled.

The roofing composition was satisfactory for export but a quicker drying material had to be devised for home use. By the end of 1953 satisfactory products had been made.

Dan Wojtulewitz looked after the solvented bitumen products. Ted and Dan together with other Polish workers were the basis of the bitumen department for many years.

Building work at Common Road in 1955 saw new buildings for the bitumen products. The first run of bitumen emulsion was on 16 August 1956 in the presence of Dr Simon, John Forman, Barry Jackson and others. Within six months the work had grown and more storage was required. Eventually there was quite a tank farm of storage vessels. At its peak 25 tons of emulsion was made every day of the week, and sometimes two batches per day. The bitumen emulsion was forced around the system by compressed air. In 1972 this caused an explosion when the end blew off a tank showering the adhesives building with bricks from the wall surrounding the tank and air compressor building. This resulting mess took some time to clean up.

Barry Jackson recalls that on one occasion when Dr Simon was out of the country a problem arose with the supply of bitumen. The acid number was crucial but Shell had changed their source and the bitumen was not suitable for the roofing product. A new supply was sourced. When Dr Simon returned Barry left him a report on what had happened and how the problem had been averted. Instead of praise Dr Simon was annoyed and quickly on the telephone to Shell to demand action. The person in relevant charge at Shell was an old friend of his and Shell representatives soon made an appearance at Stafford.

The main bitumen emulsion product was Pastel. This was used for roofing with hessian embedded in brushed layers. Roofing emulsion product was also pigmented to produce, albeit in dark tones, grey, red and green versions. There was also a trowelling grade called Paste III, and a more stable Paste Con for export. These products were adapted for DIY use as Supaproof, with weathering properties enhanced by the addition of mica.

Bitumen emulsion was mixed with rubber latex to form a rubberised bitumen waterproofer which was also an adhesive. This was sold under the Evode label of Evoseal 202. Variants were sold as own label products for several customers. These products reached a peak of about 3 million litres a year.

Dr Simon always encouraged innovation and Barry Jackson was especially adept at producing new ideas. Barry would come in to the laboratory and challenge you with, "Have you had an original thought today?"

The greatest success was Flashband. Barry had been working with many polymers and tried to incorporate them in bitumen. In particular mixtures of bitumen and polyethylene had improved flow resistance and superior adhesion. The problem was that the polyethylene separated from the liquid bitumen and floated to the surface. After a lot of work a mixture of fillers was found that allowed a stable mix to be made. The product could be used as a hot applied sealant or as an extruded strip. The extruded strip could be made in several widths on protective release paper. The strip was very tacky and did not flow under warm conditions. However as yet no practical use could be found for it. An enquiry from R M Douglas was to provide the answer. They were experiencing problems with 'climbing shuttering'. This was a technique in which concrete was poured in to steel shuttering which was bolted together with steel spacers. When the concrete had set the shuttering was unbolted and the shuttering raised to the next position and re-bolted.

The problem was that the bolts and spacers were embedded in the concrete. Attempts to stamp out washers from the bitumen strip failed because the product gummed up the stamping machinery. Dr Jackson had the idea of putting aluminium foil on one side of the strip which allowed washers to be stamped without sticking to the stamping die. This novel product was realised to have many useful features and the original enquiry was forgotten. In 1964 a patent was applied for, Grace already made a similar product with a plastic backing. They objected to the patent as did Bostik. Both were placated by the issue of free licences to make the product if they wished. Neither did so at that time. The product was marketed as Flashband for applications such as waterproofing and repairing roof ridges, making joints between lean-to structure and the main wall, sealing joints and repairing gutters roof repairs. In 1972 the product was awarded an Agreement Certificate which allowed it to be specified for use on prestigious contracts. Also at this time a grey coloured foil was introduced which gave the product more of a lead like appearance instead of the bright shiny aluminium finish. Sales grew at an incredible rate. Production doubled and then quadrupled. Later a whole new plant was specially designed. Cutting and packaging was automated. The other wonderful feature was the profitability. The unique product was sold at a considerable premium and greatly contributed to the cash flow at that time. So when problems occurred with the mass shrinking away from the aluminium foil Dr Simon soon had everyone concerned in his office wanting action. Temperature recorders put on the mixers to follow the mixing cycle and perhaps understand the process better. The result was unexpected. The night shift had a long break late at night and then rushed to catch up. The 'shrinkers' were these batches which were less well mixed. The problem was over.

In 1978 Mike Denson was transferred from adhesives to the bitumen laboratory. He made a close study of the emulsifying process. The Hurrells were past their best and not performing well. More rubbish was accumulating in the storage tanks which needed removing by hand. Quality control was Ted rubbing the emulsion on the back of his hand. Mike introduced the Coulter Counter which measured the size and distribution of the particle sizes within the emulsion. He instigated temperature measurement on the Hurrells and paid close attention to the setting up of the machines. Quality was improved.Another problem was that emulsion suitable for Evode products could only be made from bitumen from certain sources. Unfortunately bitumen was only specified by its physical attributes which were not directly associated with the required chemical properties. After an in depth study of the published information a programme of analysis was carried out to establish which material was suitable for Evode. This was achieved with a chromatography column devised from a spent fluorescent tube. In this way bitumen could be divided in to four fractions and the amounts of each measured. This was to prove vital in discussions with bitumen suppliers who tried to send materials which were unsuitable to Evode.

The biggest customer for water proofing products was Evode Roofing who was a contract applicator. This work came to an end in 1987 when Evode Roofing and its associated companies were sold to Tarmac. With the exception of Flashband production and some smaller product lines this removed the bulk of the bitumen production and further development ceased.


MV Cooksley 9 February 2006