June 5, 2021 – The phases of matter are crystal clear at the Hot Shop in the internationally renowned Glass Pavilion at the Toledo Museum of Art. Leonard Marty, master instructor of glassblowing, has his artistic juices flowing at 1500 to 1600 degrees Fahrenheit. That is the temperature range at which he can sculpt a molten mass of liquid glass (a gob) into a beautiful piece of studio glass, a solid. The process is a red hot, totally cool combination of art and science.

Leonard’s career: Artist and Educator
Leonard has been working at the museum for 27 years, the last ten as its master instructor of glassblowing. His path to a career as a glassblower began at an early age when his father gave him simple tools to use. Watching objects take shape from material he manipulated by hand captivated him.Those early experiences set him on a path to become a sculptor.

After high school, he enrolled at Bowling Green State University (BGSU) as a fine arts major with a concentration in sculpture.

As a college student learning how to sculpt, the tools were new but the process that captivated him at a young age was the same, a process Leonard discovered applied to glass as well as metal. In 1980 with a new passion for glassblowing, he was the first student at BGSU to earn a Bachelor of Fine Arts (BFA) with a specialty in glass.

“I got into the glassblowing studio and never got out,” Leonard said to Redwood Learn on March 15, 2016 at the Hot Shop.

As the museum’s Hot Shop master instructor, Leonard teaches glassblowing to students of all ages. His oldest student is 80 years young, a student who told Leonard a person is never too old to learn something new, a pearl of wisdom made of glass.

Students must be at least 14 years old to take classes due to the inherent danger of working around ovens at 2000 degrees and glass that is optimally sculpted just a few hundred degrees lower. Keeping the gob within that temperature range is essential.

At 1300 degrees, the gob enters a new phase of matter, the solid phase. “Whatever shape glass is in when it goes from liquid to solid, that’s the shape it stays in,” Leonard explained.

The artistic process of glassblowing is a constant balance of art, science, and safety.

Glass does not like to warm too quickly or cool too fast. Sudden temperature changes result in thermal stress that can cause the glass to shatter.

Holding a long, hollow steel pipe (blowpipe) with the gob at the end, glassblowers glide back and forth between red hot ovens and steel tables to keep the gob malleable. Most of their time is spent keeping the gob within the optimal temperature range, shaping the glass with tools of the trade, and adding color or other design elements to the glass. Blowing into the pipe accounts for only about 30 seconds of the process but glass artists are known as glassblowers and the process is commonly called glassblowing.

Leonard has taught more than 2,000 students during his glassblowing career at the museum.

“My first high school students are now my colleagues,” Leonard said. “And they are some of my competitors,” he added with a smile.

From chemical elements to sand to glass
The main ingredient in glass is sand (80 percent). Sand is silica or in chemical terms, silicon dioxide (SiO2). Silicon (Si) is a chemical element that comprises 25.7 percent of Earth’s crust, by weight. It is the second most abundant element and has a melting point of 2577 degrees Fahrenheit. The most abundant element is oxygen, according to the Los Alamos National Laboratory.

Silicon does not exist in nature in a free state but as oxides (sand and quartz to make glass, rock crystal, amethyst and opal – silicon dioxides) and silicates (clay for pottery, granite, and asbestos). Different crystalline structures of the atoms and other elements found in addition to silicon and oxygen account for the different materials mentioned above.

Back to the Hot Shop
Let’s go back to the Hot Shop.

The process of sculpting glass begins when a glassblower takes his/her steel blowpipe to the furnace of molten glass at 2150 degrees Fahrenheit. The furnace is always on. If cooled to room temperature, it would take 3 days to get back up to temperature, Leonard said.

The “batch” is the recipe for glass used in a studio. The museum’s batch is a combination of about 80 percent sand, soda ash so the mixture melts at a lower temperature, and limestone to give the glass strength and durability. Solid glass nuggets, called cullets, begin the process.

Color is added as the glass is being sculpted. Leonard has more than 200 choices of color. Chemical elements applied to the glass outside of the furnace give glass its color. For example, if copper or cobalt are added, glass become shades of blue. Leonard said copper is interesting because it can also color the glass red. Manganese added to glass gives it a purple color.

A glass artist’s creativity and skill transforms a gob of molten glass to a beautiful work of art, a utilitarian vessel, or both. Who said a candy bowl is not a work of art?!

A reheating chamber at 2000 degrees Fahrenheit is used to keep the glass in a liquid state so it can be shaped. In between trips to the oven, gravity can be used to add design elements by simply turning the pipe in a vertical rather than horizontal orientation.

As Leonard manipulates his blowpipe and tools, it looks effortless because of his years of experience.

Once Leonard decides his work of art is done, he removes it from the pipe and places it in another oven to slowly cool over many hours. The solid phase of matter is here to stay, maybe for thousands of years.

The lure of an artistic process, baked in science and a red hot furnance, beckons novice to master glassblowers.

“Any day I can blow glass, it’s a good day,” Leonard said.

REVIEW QUESTIONS

1. What is the main ingredient in glass?

2. At what temperature range is glass malleable?

3. How is color added to glass?

4. What is the purpose of soda ash and lime as ingredients in glass?

INQUIRY QUESTIONS

1. What do you think would have happened if Leonard cooled the glass bowl too quickly?

2. Why is studio glass both an artistic and scientific process?

3. How did Leonard’s childhood experiences provide a path to his career?