Record the original stock and the reason for change.
Identify manufacturer, range, finish, shade, grammage and any product code or merchant reference for the agreed paper. Attach the quotation revision, sample or proof that established it. “Uncoated white 120gsm” is too broad to serve as a control because many sheets can share those words while differing in thickness, surface and appearance.
Ask why a substitute is proposed: availability, minimum order, timing, discontinued stock, technical suitability or another project change. The reason shapes the decision. A short delay may preserve a colour-critical reference; a time-sensitive manual may benefit from a well-documented alternative. Neither outcome should be presumed without the project priorities.
Compare properties by their finished-job consequences.
Place the two technical sheets side by side. Compare grammage, caliper, surface, shade, opacity and grain availability where those data are supplied. Add coating, recycled content or certification evidence only when the project relies on it. Supplier values may be nominal and measured under stated methods, so do not turn a small numeric difference into a guarantee of visible performance.
A book spine relies on caliper and final extent, not gsm alone. A two-sided leaflet may rely on opacity. A workbook may need a suitable writing surface; a photography book may prioritise surface and colour response. The paper thickness explanation and opacity review keep those questions separate.
Put both papers under the same image and light.
An unprinted swatch shows base shade, surface and feel. A representative printed comparison reveals how photographs, brand colours, dark areas, fine type and reverse-side content respond. Label every sample. A loose sheet from an unidentified book is an inspiration reference, not evidence that the proposed named stock will reproduce it.
View candidates together under the lighting relevant to approval. A warmer or cooler paper changes the lightest part of the image and the apparent contrast. If the replacement moves to another print condition, the existing proof may no longer simulate it. The proofing decision should be reopened instead of carrying the old approval across a material change.
Recheck construction, weight and finishing.
Paper feeds into the whole object. Changed caliper can alter spine width, box fit and packing volume. Grain and stiffness can affect folds, opening and scoring. A coating or laminate can change touch and later handling. Ask the responsible production team which parts of the approved construction need recalculation, a new template or a new physical sample.
Postal or freight weight may move even when nominal gsm appears similar, because finished dimensions, page count, cover and packing combine. Do not promise a mailing outcome from a paper swatch. Request a calculated or representative packed weight where that result controls the commercial decision. If the item fits another component, send or identify that component too; a revised book block, carton insert or mailing pack may need a fresh physical fit check under normal handling.
Approve the named replacement, not a category.
Write an amendment naming the substitute and the comparison evidence reviewed. State whether it applies to the whole run, selected sections or one edition. Record any new spine, proof, finish or delivery consequence and the person authorised to accept it. Remove the former stock from the active production instruction while keeping the history.
If another substitute is later proposed, reopen the decision. “Equivalent approved” should not become permission to use any paper with a matching weight. The reprint control record is a useful place to preserve material identity for a later edition and to flag when a match is no longer available.