A fine black powder, about the consistency of talcum, which we mix with other ingredients to make the leaded glass waterproofing cement in our studio. Its original source was the lampshades of the lamps used in the 19th century where it accumulated as the lamp burned. The amount of this carbon deposited on the lampshade was an indicator of the purity of the oil being burned. It was necessary to scrape the lampblack off from time to time, and various uses were found for it. It is now also used to color Portland Cement, when a dark grout is desired.