Things get hot in the Marl glassblowing workshop: at temperatures between 1,250 and 1,350 degrees Celsius (2,280 to 2,500 degrees Fahrenheit) , Martin Merkel and Udo Musholt shape glass blanks into custom-made specialty components for research, process engineering, and production.
New Challenges for an Age-Old Craft
“From the blanks—1,500‑millimeter tubes with diameters ranging from three to 250 millimeters—we produce, for example, glass columns with volumes of several liters, heated glass vessels, or condensers with internal coils,” says glass coordinator Merkel. His colleague Musholt adds, “We’ve also built large experimental setups for training at various sites.” Standard items such as Erlenmeyer flasks or test tubes are not part of their offering. These are manufactured industrially and purchased by Evonik.
Merkel and Musholt learned the craft of glass apparatus construction in the 1980s in Marl, a city in the western part of Germany. Anyone who thinks the work of Martin Merkel and Udo Musholt has no future is mistaken. Especially when it comes to new products, innovative processes, or complex pilot setups, their skills are indispensable. “Of course, experimental setups have changed,” Merkel says. “That’s why we manufacture very different custom parts today than we did in the past. But the craft itself has stayed the same.”
Without the tailor-made solutions from the glassblowing workshop, forward-looking processes, products, and process developments would only have been possible at significantly higher cost and time. Particularly in process development—such as in extraction or distillation-related applications—special custom-built components are regularly required to efficiently and reliably scale up from laboratory to pilot plant. During ongoing pilot projects such as Rhamses and Rheticus, the proper repair of critical glass apparatuses also helps ensure project progress.
Let's talk!
The path to a finished instrument always begins with a conversation. “We talk directly with customers about what they need and how it can be implemented,” Merkel explains. Photos and sketches are helpful here. Once an idea is approved, the glass experts get to work. “We work for all Evonik sites,” Merkel says. “Over the years, we’ve carried out many exciting projects.”
The color of heat
The work requires care and a delicate touch. By observing the color, the experts can tell when the glass is ready to be worked. They then blow air through a tube or draw it out until the piece takes on the desired shape. “Heated glass has the consistency of honey,” Musholt explains. That’s why it must be continuously rotated during processing; otherwise it would deform. To flatten the glass, the glassblowers use special tools in various shapes.
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Working on a single piece can take several hours and cannot be interrupted. If the glass were reheated, it would instantly shatter. Once a glass component is finished, it is placed in the cooling oven—although “cooling” is relative. The annealing process takes place at 550 degrees Celsius (1020 Degrees Fahrenheit). Only under these conditions can the glass relax without breaking.
The two glass apparatus builders primarily work with laboratory glass—so-called borosilicate glass. The containers can then be used at temperatures of up to 300 degrees Celsius (570 degrees Fahrenheit). Merkel and Musholt also build apparatuses from quartz glass, which meets special requirements. It is extremely temperature-resistant, expands very little, and is highly durable. Quartz glass is not processed at typical temperatures but at 2,000 degrees Celsius (3630 degrees Fahrenheit). Grinding, sawing, and drilling glass also belong to the glass experts’ tasks.
Also a repair workshop
Because producing custom-built apparatuses is complex and expensive, many specialized instruments are repaired in the glassblowing workshop, such as glass stirrers connected to calibrated shafts. “A calibrated shaft is very expensive—replacing a stirrer blade is much cheaper,” Merkel notes. Glass joints—the connection pieces between two glass components—are also adjusted or repaired. “That’s the case, for example, when a stopper no longer fits properly on a glass container,” Merkel explains. Urgent repairs can be completed by the workshop within 24 hours upon request: “This allows our colleagues to get back to work quickly.”
The Marl Chemical Park.
The Marl Chemical Park is one of the largest chemical sites in Germany.
Around 100 production facilities operate in a tightly interconnected material and energy network, most of them running around the clock.
The production focus at the Marl Chemical Park is the conversion of petrochemical raw materials such as benzene, ethylene, propylene, methanol, and phenol into base, fine, and specialty chemicals – from C4 fractions to downstream products, from chlorine electrolysis to PVC, from acetylene to tetrahydrofuran, from fatty alcohols and ethylene oxide to surfactants, and from acrylic acid to butyl acrylate, to name just a few examples.
The glassblowing workshop is part of the analytics department within Group RD&I at Evonik Industries AG.
