Contract proof
Also called colour proof, certified proof, Chromalin, Cromalin
A colour proof printed on a calibrated proofer to the printer’s profile, showing the colours the press will achieve. In French printing it is still often called a « chromalin », after DuPont’s old Cromalin proofing system.
In practice
Judge colour on a proof made with the profile of the paper actually chosen, never on a screen. The proof comes out on a smooth white proofing stock, while a book is often printed on an offset or an ivory high-bulk paper, which absorbs the ink and softens the colours: on an uncoated paper, expect the pictures to look less vivid in the book than on the proof.
Today it is a digital proof: a calibrated inkjet proofer simulates what the press will deliver. It carries a control strip, a row of colour patches measured with a spectrophotometer; that measurement, to the ISO 12647-7 standard, is what makes it a contract. Without it, it is only a good print.
A contract proof does not replace the final proof. The bon à tirer checks the whole book, the page order, the text, the layout; the contract proof judges colour alone, and only on the pages proofed. For an art book, a catalogue or a cover with demanding colours, have the most delicate images proofed rather than the whole book.
View it under standard lighting, the daylight known as D50, and keep the signed proof: if the colours are disputed, it is the reference. Ask for it in the quote.