proof sheet
A page of proofed text; a sheet used to make corrections, emendations, etc. before being printed for use.
proof sheet: the test print before the real run
A proof sheet is a preliminary printed sample made before full production begins. It shows how the final job will look, using the same plates, inks, and paper stock (or close approximations) that will be used in the actual print run. The pressman runs a small number of these sheets, usually between one and twenty, to check color accuracy, registration, image sharpness, and overall quality before committing to thousands of impressions.
In offset lithography, the proof comes straight off the press using the mounted plates or digital plates that will run the job. In digital printing, a single-pass proof verifies file integrity and color output before queuing the full order. The sheet gets passed to the customer or the print buyer, who marks it with corrections, initials it, and returns it as the contract document. Once signed off, that proof sheet becomes the reference standard for the entire run.
Common proof-reading marks and corrections
Marks on the proof indicate deletions (strikethrough), insertions (carets and marginal notes), repositioning, color shifts, and ink coverage adjustments. A pressman will adjust fountain solution, ink viscosity, impression pressure, or plate position based on these annotations. Any significant change requires a new proof; minor tweaks like ink saturation may proceed without one. The proof also documents approval, protecting the printer from later claims that output doesn't match what was promised.
Historically, proof sheets in letterpress and metal type shops were pulled by hand or on a small hand press to allow typesetters and editors to correct typos before locking the form into the main press. The term carried over into offset and digital workflows even though the underlying technology changed completely. Digital PDF proofs and soft proofs on calibrated monitors now compete with printed proofs, but a physical proof sheet remains the legally binding reference for color and positioning on many commercial jobs, especially packaging, labels, and high-value marketing collateral.