Paging Doctor Photoshop…
Dear Word Detective: Any idea of the origin of the phrase, “doctor blade,” denoting a dull scraper used to remove ink from the non-printing surfaces of an intaglio printing plate? — James Lampert.
That’s an interesting question. The word “intaglio” rang a small, dim bell in the recesses of my mind, so I immediately began to thumb through my dusty mental Rolodex. (If you don’t know what a Rolodex is (or was), feel free to go play outside. And take that stupid telephone with you.) Anyway, I’m zipping past “impeachment,” “impetigo,” “inertial guidance” and “Inigo Montoya,” and suddenly I realize that I don’t need my memory at all. By golly, I have the internet! So I look up “intaglio.” And then I’m all like, yeah, I knew that. And I actually did, though I’m not sure why.
The short explanation of “intaglio” is that it is a method of printing in which the desired design is carved, engraved or etched into the printing plate, to which ink is then applied. The ink on the surface of the plate is then removed, leaving ink only in the grooves of the design, so that when the plate is pressed against paper or another medium, the design is transferred. Often used for documents, stamps, etc., intaglio printing gives a slightly raised or “embossed” feel to the design. The word “intaglio” is Italian, meaning “engraving” or “engraved work,” from the verb “intagliare,” meaning “to cut into or engrave.”
The name “doctor blade” for the implement used in intaglio printing and similar technologies is fairly recent, the earliest citation in the Oxford English Dictionary (OED) for the term in print being only from 1961, though we can assume it’s actually somewhat older. The word “doctor” itself is, of course, much, much older, first appearing in English around 1300. The root of “doctor” is the Latin verb “docere,” meaning “to teach,” and in English it initially meant simply one who, by experience or training, was qualified to teach others. Originally applied to senior religious authorities, by the late 14th century “doctor” had acquired an association with the highest degrees of learning, and thus the qualification to teach, at a university.
But also in the late 14th century, “doctor” came to be associated with a highly-learned practitioner of medicine, and now we’re getting close to the logic of “doctor blade.” As a verb, “to doctor” originally meant “to treat medically,” but gradually acquired the broader figurative senses of “to repair or patch up” (“Wasted most of the morning in doctoring a clock,” 1829), as well as, to quote the OED, “To treat so as to alter the appearance, flavor, or character of; to disguise, falsify, tamper with, adulterate, sophisticate, ‘cook'” (“By a few touches of a file on the milled edge, a coin can be so ‘doctored’ as to fall almost invariably heads or tails at will,” 1884).
“Doctor blade” employs the “repair or patch up” sense of “doctor,” and there are apparently all sorts of gizmos in various fields bearing the name “doctor.” The OED defines this special sense as “A name given to various mechanical appliances, usually for curing or removing defects, regulating, adjusting, or feeding.” Calico fabric printing, for instance, at one time required the use of a “cleaning doctor,” a “lint doctor,” and a “color doctor” (“The superfluous color is … wiped off by the color doctors… These doctors are thin blades of steel or brass, which are mounted in doctor-shears, or plates of metal screwed together with bolts,” 1875).
So a “doctor” in this mechanical or tool sense is a device which either removes defects or prevents them from being created in the first place, which certainly fits with your description of a “doctor blade” used in intaglio printing. In fact, the same term is also used in offset printing (“Doctor blade, a ‘knife’ of rigid plastic or thin sheet-metal which presses against the gravure press cylinder, and which wipes away ink from the surface of the cylinder,” 1967).