In glass-blowing, red is the most difficult color to make. If the glass gets too hot as the color is added, it can turn brownish-yellow. Red, however, is the color at which glass artist Donald Carlson excels. “Most of the colors, you can make easily, but with red, there are a million variables such as time, temperature and how you work the glass,” says the 62-year-old. “I’ve devoted my whole career to making simple, elegant shapes in red.”