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Glassblowing Basics: Color Application, Part 2

Updated: Feb 13

I have taken too long of a break but I am back with another blog post. And you know what they say... better late than never. I hope 2024 is treating you well thus far. :) I am feeling good and optimistic for the year!

Now, onto my favorite thing.. Color!

From top left to right: Minami and Jeanine are pulling white cane. The white looks yellow due to its heat, but will turn white as it returns to room temp. / Clear cane pulled with inclusions of mica, made by Minami Oya / This is one of my favorite murrine vases I own, by Herb Dang / Close up of Dave Patchen's twisty cane. / One of my simple clear vases with white canes.

white reticello glass bowl by Dave Strock

Above: Dave Strock of Manzania Glassworks' reticello bowl. Two layers of cane twisting in opposing directions capture bubbles in between.

I'll start with one of the most popular coloring techniques in glass, which is using cane and murrine. Murrine is also called mosaic glass, and in the Italian tradition, you may recognize it as millefiori, which is characterized (usually) by small, intricately composed, floral decoration. Cane is glass rods pulled and cut into desired lengths, which are picked up on the end of a pipe to create linear patterns. Cane can be made clear, colored in numerous ways, twisted, and/or if desired, used as the building blocks of murrine to create images or patterns. Due to the small diameter of cane, which ranges from about .5cm to 1.5cm, it's resilient to thermal shock and will self-anneal. Thinner rods of glass are typically called stringers, which can be rolled onto glass directly without preheating upon application. The squiggles that I make for my Blahbs and Squiggles glasses are stringers shaped into coils! Thick glass canes need to be cooled in the annealer, as with any murrine, especially because they are thicker and made with multiple colors, making them susceptible to stress. Properly annealed murrine can be cut into cross-sections of desired thicknesses that are ready to be used in blown vessels. This method has a lot of overlap with the Japanese ceramic technique called nerikome (I learned about it from The Great Pottery Throw Down, thank you very much! I love that show). On a related note, there are many creators who work similarly with polymer clay! Anyway, murrine doesn't always involve cane as you can shape and combine color bar into any design. You can even shape murrine into letters - it's very cool!

From top left to right: A piece of murrine by Ethan Barnes. / Colorful canes are picked up on molten glass to make my Blahbs and Squiggles cups / Blahbs and Squiggles Cups / Page taken from Richard W Price. 2001. The Corning Museum of Glass, A Guide to the Collections. (Corning, New York, The Corning Museum of Glass) p.130

Enameling is another coloring technique, which involves suspending metallic oxides in a medium that allows for painting on glass. The enamel needs to be fired in a kiln so that it permanently adheres to the surface, but at a relatively low temperature so as to not compromise the integrity of the glass itself. When I think of glass enameling, early Egyptian glass and intricately painted Venetian chalices and goblets come to mind. It's not my area of expertise, but given my interest in painting, I'd like to try it one day. Maybe I feel a little intimidated by the process, but I don't have any reason for having these reservations. Perhaps 2024 is my year to try (?)

One technique I will most likely never mess with is fuming. From what I know, fuming is widely used in lampworking, but not as much in the kind of glassblowing that I do. My hunch is that it has to do with the small scale of lampworking, but the process is toxic regardless of size. Cost is probably another factor, as fuming gold and silver (or whatever else can be used) is easier on a pendant rather than on a 20 inch vase. Anyway, the dangers of this technique comes from imparting the glass surface with the off-gassing fumes that get released by burning the coloring agent. As you can imagine, without adequate ventilation, this is bad stuff for your lungs. Stannous chloride is a colorant that can produce an iridescence by fuming as well. You may recognize this sort of iridized glass in works by Louis Comfort Tiffany or Frederick Carder for Stueben Glass. Watch the video below - it's interesting!

Although it's not entirely the same thing, you can achieve a similarly iridized glass surface by using certain colors that are prone to reduction. Reducing colors produce a metallic finish that can be multi-colored, but the color has to be on the exterior for the desired effect to take place. Reduction can occur by exposing the glass to an environment that is deprived of oxygen, or at least low in oxygen and high in gas/flame. (If you understand this on a molecular level, please let me know, as I only know through experience.) You can create a low air, high gas environment in the gloryhole or use the fluffy torch on the glass to achieve the metallic look. Some people confuse reducing colors with striking colors, but they aren't the same thing. Striking colors are affected by temperature rather than levels of oxidation.

The black color bar on the left has a reduced surface. Once heated and encased, the metallic sheen should disappear, but this color in particular seems be really sensitive. / You can see that the butterbell on the left has a yellow band in the middle because it was made using a striking color. Photo credit: Maci Noble.

If you want to read about the tools I was referencing in this blog, you can find it in my previous posts about glassblowing tools. Part one + Part two

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