Jill Butler Yellow Striped Tumbler. Illustrator Jill Butler's charming designs radiate joie de vivre, a delightful result from living in France for part of the year. Jill's wonderful Yellow Striped tumblers are made in Germany at famed RKL Ruhr Kristall Glas AG in Essen. In business since 1923, RKL's machine-blown drinking glasses are screen printed with glass ceramic colors and then burnt in at a temperature between 580 degrees C and 620 degrees C to ensure that the glass is dishwasher safe.