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Glassblowing is a scientific art form that uses heat to melt and form glass into intricate and versatile objects. To make a simple glass paperweight, a glassblower dips a long, metal, hollow tube, called a blowpipe, into a batch of molten glass. Several tools are used to form the glass as the blowpipe is rotated manually and the shape of the paperweight begins to emerge. Scientific glassblowing uses many of the same principles of decorative glassblowing to make scientific instruments with the aid of specialized equipment. The degree of automation and craftsmanship required often depends on the type of instrument.

Some instruments, such as test tubes, need to be fabricated with precision in large quantities for mass consumption. Many are made in glass manufacturing facilities with automated equipment. There are, however, some instruments that require significant customization. For example, a chemistry research lab at a university may need only one instrument or system for a specific experiment wherein the glassware’s functionality is more critical than its precision.

This is where the skills of scientific glassblowers like Neal Korfhage come into play. Korfhage, head of the Department of Chemistry and Biochemistry Glass Shop at the University of Wisconsin-Milwaukee, is a part of a niche industry which tailors to a customer’s unique requirements. At times, it may be more convenient to buy certain glassware from a glassblowing company. “But if you want customization and a quick turnaround time, and the ability to have a consultant, then it doesn’t make sense to [purchase mass produced glassware] because those companies can’t do that for you,” says Korfhage.

In Terminator 3, T-1000 is a liquid metal robot that can contort itself to any shape. Korfhage alludes to the robot when I ask about the prospect of automation replacing custom glassblowing. “You’d need an AI (artificial intelligence) on that level to be able to basically almost perfectly mimic a human. Machines can do one thing really well with our current technology. With complicated stuff, with what I do, I just can’t see it happening without a superhuman AI that’s self-aware and can do its tasks all on its own.” While some aspects of scientific glassblowing may be automated, there are many facets that require a human touch.

Korfhage has assisted many research groups at UWM, particularly those related to organic chemistry, physics and engineering. Much of his time is spent designing and fabricating distillation instruments, where a liquid is purified and separated into its individual components¹ .

He also makes complex glass manifolds for ultra-high vacuum systems, which consist of a mechanical vacuum pump and a metal chamber inside which a specific reaction occurs. A manifold is a pipe with multiple outlets² and in an ultra-high vacuum system, serves to remove any oxygen from the sample being studied to prevent contamination.

Glass manifold constructed by Korfhage for ultra-high vacuum system

Korfhage also repairs instruments for external scientific firms in the Milwaukee area. Korfhage primarily works with Pyrex or borosilicate glass, used commonly to make laboratory glassware³. To fabricate instruments, Korfhage uses a few pieces of equipment: a glass-working lathe, several types of blowtorches, and a blow hose. A glass-working lathe is used to rotate the glass he’s working with, known as a “workpiece.” Each end of the lathe has a chuck, a type of clamp that holds the workpiece as it rotates. In this way, the lathe rotates the glass as it melts evenly and is formed into a specific shape.

There are two most commonly used types of torches. A precision torch is used to produce a fine-tipped flame. In contrast, a melting torch produces a larger flame used to warm up workpieces over a larger surface area and is useful when working with large workpieces. A blow hose is used to blow air onto the workpiece to control the shape of the glass as it melts.

Before demonstrating his art, Korfhage dons his personal protective equipment. This  may include didymium glasses. As Pyrex melts, the sodium within emits an orange light that can damage eyesight with specific visible and UV light4. Didymium, a specific mixture of the elements praseodymium and neodymium5, is used in the safety glasses to filter out the harmful emitted orange light4.

To illustrate how glassblowing works, Korfhage demonstrates a few techniques. Using a hardened steel knife, he makes a score mark in the middle of a hollow tube. He exhales onto the score mark to add moisture and snaps the tube in half to demonstrate the process of snapping.

Scoring a single glass tube (left) to produce two tubes (right)

He then performs the following steps to demonstrate how to fuse the two pieces together:
1. Clamp each tube on the chuck on either end of the lathe.
2. Attach one end of the blow hose to a neoprene stopper.
3. Insert the stopper end into one of the hollow tubes, on the side affixed to the chuck.
4. Power on the lathe so that glass tubes rotate and move slowly toward each other.
5.  When the tubes are almost touching, use precision blowtorch to warm up the glass.
6. Increase heat with the blowtorch.
7. As the molten glass starts drooping, blow gently into the blow hose’s mouthpiece to move the molten glass upward so it doesn’t collapse.
8. Remove torch to let glass cool down.

Glassworking lathe with two glass tubes mounted onto chucks (left), fusing the tubes with a precision torch (center), single fused glass tube (right)

The result is a single hollow tube, fused at the center. Korfhage inspects the glass under a polariscope, a device that shows the degree of thermal strain in glass6. Two thin blue rings are visible on either end of the joint where the glass tubes were fused, indicating the location of thermal strain. As Korfhage applies a little pressure on the joint, a section of the tube changes from blue to red indicating an area of increased strain.

Fused glass with strain rings (left) and gradient of internal strain in glass when pressure is applied (right)

If this piece was meant for a customer, Korfhage would place it in an oven for annealing, the process of heating and cooling a part to relieve stresses in the material7. Annealing removes the strain rings and prevents the tube from shattering from the strain.

Glassblowing appeared to be second nature to Korfhage; the entire process of fusing the two tubes and inspecting them took less than four minutes.

Korfhage was exposed to glassblowing at a young age, by his father,
a scientific glassblower at Albemarle Corporation who built a small glass shop attached to their house. Korfhage was fifteen when he made his first glass pieces under the tutelage of his father. His propensity for working with his hands, problem solving and an aptitude for science fueled his desire to become a scientific glassblower.

After enrolling at the Scientific Glass Technology program at Salem (NJ) Community College, Korfhage worked at MilliporeSigma, and progressed to the position of senior glassblower over the course of 11 years before coming to UWM.

Korfhage plans to continue to provide his expertise to several research groups at UWM. He also continues to build on many opportunities to impart his knowledge and skills to the glassblowing community in the area. He teaches an introductory glassblowing class at UWM geared toward graduate students that provides them with a high-level understanding of the work that goes into making the instruments many of them use. He also teaches a seminar with a team of glassblowers at the annual symposiums held by the American Scientific Glassblowers Society.

Korfhage has witnessed how automation has benefitted the glassblowing industry, particularly in making common pieces of glassware. “But test tubes and coffee pots are so far away from a manifold or distillation equipment; it’s multi-faceted,” says Korfhage. While automation has its advantages in industry, the mastery and craftsmanship provided by a more human touch has helped labs make strides in innovative scientific research.

To learn more about Neal Korfhage, Salem Community College or American Scientific Glassblowers Society, visit the following websites:
Salem Community College:
American Scientific Glassblowers Society:

1. “Distillation”. The Essential Chemical Industry – Online. Accessed January 28, 2019.

2. “Manifold”. Schlumberger.  Accessed February 2, 2019. “”

3. “What is Borosilicate Glass?” Qorpak. Accessed January 28, 2019. “”

4. “Rose Didymium Glass (S-8801) Technical Data”. The Scientific Glassblowing Learning Center. Accessed February 2, 2019. “

5. “Didymium Facts and Uses”. ThoughtCo. Accessed February 17, 2019. “”

6. “Polariscope”. U.S. Food & Drug Administration.  Accessed January 28, 2019. “”

7. “Manufacturing Technology”. Bright Hub Engineering. Accessed January 28, 2019. “”

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