Glass is a noble and beautiful material used to produce both functional and decorative objects, including glasses, decanters, stemware, jugs for drinks, and a vast array of other products.
Centuries ago, the man mastered a technology for glass manufacturing, and uses this skill to this day. Although today we have technologies for large scale manufacturing of glassware, yet still there are places where these new processes are combined with experience, knowledge and skill of manual work. One of them is Krosno Glass glassworks.
A concept for a new collection arises first in the designer’s mind, but then it has to be transferred onto paper and then transformed in a digital model.
We created a new premium brand, Krosno Design, using designs from the world class industrial designers. For example, we are a partner of Karim Rashid, one of the top designers, but our portfolio also includes deigns of other, maybe less known, but dynamically developing designers.
Then 3D printouts are prepared, to see how a given object will look in real life. Resin materials, imitating glass, can be used for prototyping. When the designers’ concept is ready, the production department can start its work.
A glass batch, i.e., mixed materials, including silica sand - the main component, is prepared at the batch plant. The sand makes up 70% of the glass composition. The noble “crystalline” glass is used for manual production, and for production of stemware at the mechanical department.
The production technology depends on the product type. Items of more complicated design are produced manually. Products manufactured in large series are produced mechanically.
Let’s have a closer look at manual work. First, moulds have to be manufactured. These used for short series are made of hard beech wood, while cast iron moulds are used for larger batches. They are lined with cork, so the material can be rotated during blowing. Moulds for small items, e.g., decanter stoppers, are made of soft glacial stones. A lot of manual work is involved already at this stage. The glassworks still need specialist skills of model makers, stonemansons, turners, or even a smith, who prepares tools for glassblowers.
Let’s move on. Nine teams work on a working platform of the glass furnace unit, and they can prepare 9 different product types at the same time.
The furnace is equipped with a tank of 75 tonnes capacity. The glass batch is fed into this furnace, and there it is melted at 1500 degrees Celsius, to form colourless melted glass. Various chemical compounds are added to raw materials to obtain coloured glass, e.g., cobalt oxide is used to produce blue glass, while a mixture of different compounds gives black glass.
Here a jug is produced. After forming, the product is cut from the blowpipe. It has to be heated in the glory hole, and the excess material is cut off. This way, the rim is shaped, and then the opening is formed. Finally, the handle is added.
Let us also see how flower vases are produced by a press-blown technique. The glob is formed of coloured glass, and then colourless mass is gathered onto it. The vase shape is blown in a mould, but without rotating. This way, non-cylindrical products are manufactured.
After manufacturing, products are transferred to the lehr. Here, they are cooled under controlled conditions, to prevent accumulation of stresses.
After cooling, quality control is performed. Our next stop is the Processing Department. Here, we can see stem glasses. After cutting off the technological excess, rims are polished: external and internal edges are compressed. To ensure the stem glasses can be used safely, their edges are melted.
Finally, decorations are made. First, cuttings are made, which are then ground, according to the design. This is how finished products from the Handmade Production Department look.
For comparison, we will visit the Mechanical Production Department. The process follows the same route; however, work is fully automated.
The material is melted at 1500 degrees Celsius. A glob of glass is cut at automate stations, and delivered to a marver. The blown bubble is formed in a mould. After forming, the glass is cooled, similarly as in the Handmade Production Department. Then the excess glass is cut off, and the rims are ground and then melted.
This stem glass was produced using a set of two feeders. The bowl is made from the first glob of glass, while the bottom is manufactured by a pressing method. Then the bowl and the bottom are joined together, and the stem is pulled out.
Finally, we will take a look at the laboratory. Here, the chemical composition of the glass is verified on a regular basis, and stresses in the glass are determined. Clear glass colourlessness is checked using a spectrophotometer.
Krosno Glass manufactures over 6 million pieces of glassware every month.