as Professor of Industrial Chemistry at the University of the Philippines from 1922 to 1934. In 1923, he started the Quisumbing Ink Products company, and in 1934, founded the Quisumbing School of Technology. According to a book published in 1960, Quisumbing inks then enjoyed an exclusive contract to supply all branches of the Philippine government. Quink was later manufactured in the Philippines under license from Parker, and the bottles were labelled accordingly. Features The success of Quink lay in its useful features: it had the desired quality of ink flow, it resisted water and molding, it was non-corrosive, and it was claimed to be quick-drying. From the beginning it was advertised as containing a "secret" additive which purportedly dissolved sediment and reduced clogging. In 1942 this additive was given the trademarked name "Solv-X". Quink was developed and introduced when the Duofold was Parker's flagship line, but the Duofold's successor, the Vacumatic was already under development and was in full production by 1933. Vacumatics held their ink supply directly within their celluloid barrels, so Quink was formulated accordingly. Quink is not to be confused with two iterations of a special ink formulated exclusively for use in the Parker 51. This ink was highly alkaline and while water-based, also included a substantial amount of isopropyl alcohol. It was released in 1941 as "51" ink, along with the Parker 51 pen; in 1947 it was made somewhat less corrosive, and renamed "Superchrome". Parker was careful to print prominent warnings on caps, labels, and boxes that the ink could only be used in the 51 (and, later, its economy version, the 21), and would damage any other pen. Prior to the full public introduction of the Parker 51 in 1941, selected market testing of the new pen was carried out, starting in 1939. Since the 51 and its special ink had been designed together as a complete system, the new ink was given limited release in tandem with the market tests under the name "Double Quink". By all evidence, Double Quink was not advertised to the general public, and the name was dropped once the 51 went on general sale. Actual surviving examples of Double Quink bottles would appear to be vanishingly rare: not a single photo appears in the Shepherds' authoritative and officially-sponsored Parker 51 monograph, despite the researchers' access to Parker's own archives as well as collections worldwide. Twenty-first century According to