75 days of blue

In the production of bottles and other glass packaging, glass usually acquires special colours only in the last preparatory step before it is moulded. In what is called the feeder, which reprocesses the glass mass from the large furnace, the colouring components are added and worked into the mass before the gobs are portioned for the glassmaking machine. This enables the colour to be changed very quickly, because only a very small part of the mass is coloured. Furthermore, several production lines can be supplied with different glass colours from one glass furnace.

Changing the colour of a furnace

Blue is a special colour for glass packaging that Vetropack has known well for a long time. Let us take as an example the Croatian subsidiary in Hum na Sutli, which has been producing blue bottles for various customers using the feeder process for more than ten years. The task facing the production plant in Nemšová, Slovakia, in 2019, was much more ambitious. It was to take over the production of the blue bottles on a large scale, as part of a campaign for various international customers in the region.

Tonnes of blue glass, immense quantities: this is also possible with the feeder process. However, changed constraints ensure that the calculation is different. What is a good solution from an economical perspective for small and constantly changing batches is not ideal for a large throughput that has to be maintained over a long period of time. So a technical alternative was soon discussed. If the colour is not going to be changed, why not just set up the entire production process for one colour for a certain period of time?

For the blue glass campaign, a white glass furnace was completely converted for the production of blue glass. The furnace had been overhauled only a year earlier and the glassmaking machines had been refitted for the narrow-neck press-blow method for the production of bottles. This gave them a good head start, but such a changeover is still no easy matter from a technical standpoint, and can only be implemented with a detailed schedule.

A combination of know-how and commitment

Nobody knows this better than Robert Bestro, who coordinated the project and provided crucial support to the project managers. Actually a sales manager for wide-mouth jars and bottles in Nemšová, he was the one who brought everything together. Bestro knows the entire chain from technology and manufacturing processes to quality assurance, packaging and logistics.

“With the tight schedule I worked up a sweat more than once,” says Bestro, who was soon known throughout the plant only as “the Blue Man”. “But fortunately, everyone involved was extremely committed and contributed a great many ideas. Such a project simply requires many heads and many hands, and we have them here in Nemšová”.

In fact, all departments of the Slovakian plant were involved in the preparation, while normal work continued in parallel. There are decisive differences in the production processes when the colouring of the glass mass is carried out in the furnace instead of in the feeder, which meant that a lot of thought had to be given to many things. Precise process control is critical for quality, and for precisely this kind of monitoring and control of the processes in the melt there was no empirical data available for the colour blue. For one thing, the chemical composition of the glass mass and colouring additives is different from those used for colouring in the feeder. Deviations in the feeder are easier to monitor and only lead to small losses of time and material, whereas deviations in the large furnace are much more difficult to control. So a lot depends on working technically with very tight tolerances.

Group-wide project

Just how well prepared the project was in the end was reflected in the excellent quality that the Slovakian plant was able to deliver – practically from a standing start – and then over the planned 75 days of continuous operation. Quality assurance was organised with very close cooperation and daily discussion between production and technical staff, so that minor problems were solved without delay.

In the course of the project, the advantages of switching to the new process became apparent. For example, the job changes that would otherwise be due every three to four days could be omitted. A job change involves, among other things, changing the moulds in the glassmaking machines, adapting the quality controls to the new production run and changing the processes for palletising and interim storage. Large series and quantities therefore ultimately mean significant savings in terms of time and effort.

The fact that Vetropack’s Slovakian plant was able to concentrate entirely on the colour blue also reveals another synergy effect – collaboration within the Vetropack Group works smoothly. The Croatian sister plant can still take on orders for blue bottles and jars using the feeder process if necessary. However, as Nemšová was not able to produce any wide-mouth jars and glass bottles in white during the blue glass campaign, production was relocated.

Robert Bestro’s conclusion is positive: “There was fruitful collaboration between all employees, who were happy and enthusiastic about working on the project. Everybody was thinking about how to make things better, easier and more efficient”. The “75 days of blue” are a success story for Vetropack. Not only for Nemšová, but for the whole Group.