Reusche Glass Paint - Tracing Black #61 (Lead Free)
Reusche Tracing Black 61 #57R003.
From Schilling inc's Lead and Cadmium Free series, which have a wide firing temperature range of 615-760C. This series have become a popular alternative to the traditional glass stainers.
At the low end of the firing temperature range, it will fire a bit matte. The higher you fire them, the glossier the finish becomes.