lean
Of a character which prevents the compositor from earning the usual wages; opposed to fat.
lean: text that pays poorly for the compositor's time
In hand composition, lean copy meant typesetting work that yielded below-average wages because the text itself was uneconomical to set. A compositor working from piece rates earned money per unit of output, but lean composition offered fewer characters to set in the same reading time, or required extra handling that slowed production. This was the compositor's problem, not the printer's or customer's.
What made copy lean? Narrow columns forced frequent hyphenation and line breaks. Extensive punctuation, mathematical symbols, or special sorts interrupted the flow of standard letters. Badly formatted manuscript with irregular spacing or unclear abbreviations required constant decision-making. Poetry, with short lines and ragged composition, was notoriously lean. So was any text requiring frequent font changes or correction stops. A compositor could produce perhaps 2000 characters of fat, steady narrative in a day; lean work might yield only 1200.
The opposite condition, fat copy
Fat composition was a compositor's preferred work: long measure, simple punctuation, uniform font, clean manuscript, minimal special characters. Novels and standard prose were fat. A job full of fat copy meant a compositor could maintain steady hand speed and earn full day-wages. Newspapers, which needed speed and paid by the piece, naturally generated lean composition from their short columns and heavy punctuation, yet the volume made the work valuable overall.
The term reflected the economic reality of printing before hot-metal machines. A compositor's income was entirely dependent on output speed. Lean work was not bad work; it was simply slower work, and slower work meant lower daily pay. Printers understood this and adjusted rates for lean compositions, though this negotiation was a constant source of friction in the printing trade.
The distinction became obsolete with linotype and monotype machines, where character-per-hour rates were determined by the machine's mechanics rather than the compositor's skill or the copy's format. By the mid-twentieth century, the terms lean and fat were already archaic, surviving only in trade memoirs and union records.