Borosilicate Glass vs. Soft Glass – What's the Difference?
By Bryn Cavin, Marketing & Content Manager
With Joint Venture coming up on April 19 & 20, we’ve received some questions about the differences between soft glass and borosilicate glass. To explore these queries, here are some examples of works currently on view in MOG’s galleries which were made using each type of glass.
So, what is the difference?
Soft glass (soda-lime glass) has a relatively high coefficient of expansion. This type of glass, melted in the furnace and then shaped and sculpted, is what one most commonly sees used in the Museum Hot Shop. It melts at lower temperatures but is more sensitive to extreme heat and cold and is therefore susceptible to shock. To learn about how the furnaces in MOG’s Hot Shop are charged – that is, how the soft glass is loaded into the furnaces – please read “The Care and Feeding of the Glass Furnace” by Greg Owen.
Borosilicate glass (hard glass) has a relatively low coefficient of expansion, which makes it resistant to thermal shock. This allows the glass to withstand extreme changes in temperature. Borosilicate glass must be melted at a much higher temperature than soft glass but allows the artists using it to be very exacting.
A soft glass sculpture by Richard Royal in the reheating chamber.
Turtle Anuweh creating a borosilicate humpback whale rig at Chronic Heat: A Joint Venture (2024). Photo by Jamie Zill.
Soft Glass in the Galleries
The majority of the pieces in MOG’s Permanent Collection are made from soft glass, so you will see many and varied examples of its use in the galleries. Here are some of the soft glass pieces currently on view in our exhibitions.
Traditional Cedar Bark Berry Basket
Corwin N. Clairmont (Member of the Confederated Salish and Kootenai Indian Tribes, born 1947). Made at the Museum in 2009. Blown and hot-sculpted glass; 16 × 20 × 22 inches. Collection of Museum of Glass, Tacoma, Washington, gift of the artist (VA.2010.19). Photo by Duncan Price.
A still life focuses on objects that are arranged into a composition. Much like hyperrealistic paintings, sculpting real-life objects is a showcase of artistic skill. Often, there is more to these groupings than meets the eye – the relationship of these objects frequently serves as a reflection of underlying cultural, social, and economic contexts. About this large-scale, blown-glass still life, Clairmont wrote, “The cedar basket is a reminder of the place we live, and a direct connection with our ancestors and the important lessons embedded in this wonderful form. Creating the cedar basket in glass is also a reminder of the fragileness of many things that the natural world provides, enabling the human being to survive. We need to be respectful of each other and that which makes up the natural world we live in. All is connected and a part of the great circle.”
On view in Out of the Vault: Art History 101.
The Stinger Series
Left to right:
Kitty Pryde Stinger
Nancy Callan (American, born 1964). Made at the Museum in 2023. Blown glass.
Catwoman Stinger
Nancy Callan (American, born 1964). 2022. Blown glass.
Mystique Stinger
Nancy Callan (American, born 1964). Made at the Museum in 2023. Blown glass.
The comic books that inspired Callan’s Stinger series were an important part of her childhood. Iconic costumed characters such as Batman and Captain America inspired the early works in this series. Recent works focus on strong female characters like Kitty Pryde, Catwoman, and Mystique. Their backstories are intriguing to Callan, who has herself become a role model for an up-and-coming generation of women working in hot glass. The Stingers in Forces at Play are some of the largest Callan has attempted in her career; their sheer scale is a testament to Callan’s own superhero persona as a glassblower.
On view in Nancy Callan: Forces at Play.
Rider
Gabe Feenan (American, born 1973). Made at the Museum in 2016. Blown and solid hot-assembled glass; 30 ½ x 10 x 8 in. (77.5 x 25.4 x 20.3 cm.). Collection of Museum of Glass, Tacoma, Washington. Gift of the artist.
Although you’ll often see him working on other artists’ pieces as one of the members of MOG’s Hot Shop Team, Feenan’s personal work evokes strength and balance with their stacked geometric shapes. Relying on pure ability and technique, Feenan seeks to emphasize the importance of a skilled artist’s hand in a machine-made world.
Rider was selected from the Museum’s Permanent Collection to be included in Glass in Bloom as an inspiration for ikebana artists. Ikebana is the traditional Japanese art of flower arranging. Unlike Western floral design, which focuses on fullness and color, ikebana follows a more minimalist approach, using line, space, and asymmetry to create a sense of movement and natural beauty. Rooted in Zen philosophy, it often incorporates branches, leaves, and even empty space to evoke a deeper connection to nature.
On view in Glass in Bloom: An Ikebana Exhibition.
Adrift (Sea Turtle)
Raven Skyriver (American Tlingit, born 1982). Freehand-sculpted and hand-carved glass; metal stand. Courtesy of the artist and Stonington Gallery, Seattle, Washington.
Based in the San Juan Islands of Washington State, Skyriver often collaborates with his wife, artist Kelly O’Dell, to create sculptural work based on their island upbringings, with the purpose of examining nature and the diversity and fragility of marine ecosystems. Their work has been exhibited nationally and abroad to bring awareness to human impact on the natural world. About his work, Skyriver says, “I attempt to place the creatures back in their environment by capturing the fluid nature in molten glass and transferring it into the perceived weightlessness of a swimming creature. I always strive to imbue the work with a hint of life.”
Currently on view in Field Notes: Artists Observe Nature.
Borosilicate Glass in the Galleries
Because of its ability to withstand high temperatures differently than soft glass, borosilicate glass can be used to create tiny, intricate designs. Here are some of the borosilicate pieces currently on view at Museum of Glass.
Entomological Specimens
Vittorio Costantini (Italian, born 1944). Hot-sculpted glass. The George R. Stroemple Collection, A Stroemple/Stirek Collaboration. Photo by Duncan Price.
Constantini was born on the island of Burano in the Venetian lagoon. Although he apprenticed on Murano, the epicenter of Italian glassblowing, he taught himself the techniques of flameworking. The hallmark of his studio practice has been his interest in realistically representing a vast variety of animals. While Constantini creates naturalistic fish, crustaceans, birds, butterflies, and amphibians, his strongest interest is in the realistic depiction of insects, particularly the order of Coleoptera, commonly known as beetles.
On view in Field Notes: Artists Observe Nature.
Cubism III Meander…Bisect from Matrix Series
Brent Kee Young (American, born 1946). 2009. Flameworked borosilicate glass rods; 21 3/4 × 21 × 22 inches. Collection of Museum of Glass, gift of the Robert M. Minkoff Foundation. Photo by Dan Fox, Lumina Studio.
The pieces in Brent Kee Young’s Matrix series are made up of intricately flameworked borosilicate glass rods arranged in a webbed pattern. Young was inspired by the matrixes created by entangled piles of rebar and building rubble next door to his art studio, as well as by the tangle of lines created when dirt is shaken out of a plant’s root ball. Young writes, “I am interested in the ambiguous nature of glass and the sense of space and volume one can create. Of course, the study of how light is controlled and affects and defines each work is an utmost curiosity. This new work, the Matrix series, offers a refreshing way of approaching inquiry into these mysteries.”
On view in Out of the Vault: Art History 101.
Natural Botanicals Series
Left to right:
Three Figs
Kathleen Elliot (American, born 1958). 2009. Borosilicate glass; 15 × 10 × 4 inches. Courtesy of the artist.
Apricots Still Life
Kathleen Elliot (American, born 1958). 2021. Borosilicate glass; 15 1/2 × 12 1/2 × 4 inches. Courtesy of the artist.
Elliot began her Natural Botanicals series in 2003. These three-dimensional sculptures portray plants, fruits, and vegetables. “I love the surprise of viewers realizing that these seemingly organic and pliant pieces are actually glass,” Elliot says. “These works celebrate the beauty of nature and its ability to lift us out of the commotion of everyday life that seems so urgent and important, reminding us we belong to mysteries far greater.”
Elliot is so invested in creating botanical specimens as realistically as possible that she brings actual fruits, vegetables, and leaves into the studio, working from life to make sure that each detail is accurately represented. Her work pays tribute to, and continues, the traditions of botanical illustration, still life, and trompe l’oeil (deceive the eye) painting.
On view in Field Notes: Artists Observe Nature.