Digital Printing “Approval Sample Archives”: 3 Practical Record-Keeping Methods — Sealed Samples / Color Cards / Proof Photos — Which Can Serve as Evidence in a Color Dispute?

In August 2026, a home appliance customer raised an issue. Their product cartons featured a logo printed in a specific spot color. After a batch arrived at the customer’s warehouse, quality inspection reported that the color was off, and the customer requested replacement or return of the entire batch.

This batch had been printed according to the physical proof approved by the customer. The proof approval form carried the customer’s signature, and we had also retained a sample.

The problem was this: when the sample was approved, it was viewed under the lights in our workshop.

The customer’s warehouse used 5000K cool lighting, while our workshop used a D65 standard light box. Under these two conditions, the same sample looked different.

Ultimately, the batch was not fully returned—the customer accepted it. However, from then on, their procurement process included one additional requirement: a color card was required instead of a physical sample.

This incident exposed a highly practical problem: printers have been retaining samples for decades, but most do only half the job. They retain physical samples without color cards, take photos without recording light-box conditions, and keep paper proofs without preserving the machine settings used for proofing. When a genuine dispute arises, every record is incomplete in some way.

The focus of a dispute is never who made the printing error—if it were printed incorrectly, the customer would reject it immediately rather than wait until warehousing. The focus is whether what I see is the same as what the product is supposed to look like. To defend that position, a printer needs not one retained sample, but a set of mutually corroborating records.

Below are three types of archives. Each addresses a specific problem.

Archive Type 1: Sealed Physical Samples — Establishing Which Version Was Used for the Batch

A sealed physical sample is a necessary condition, but it addresses a very specific question: after the customer approved the proof, did we change anything without authorization.

We encountered a problem that illustrates this point. For a gift box order, the customer approved the proof and we retained a sample. During production, the press operator said, “The coated offset paper does not feel right for this color, so I changed it,” and substituted the paper without telling anyone. The ink film had not changed, but the paper’s base color and absorption properties had changed, producing a visibly different color.

When the customer inspected the goods, they said the color was incorrect. We presented the retained sample and said, “Look, this is the color of our retained sample.” The customer replied, “The retained sample was printed on the old paper. What I am seeing is on the new paper.”

This demonstrates that a retained sample must be sealed using the same batch of materials, the same batch of inks, and the same machine as production, and under the same environmental conditions. Otherwise, it can only prove that we once produced one sample, not what the production run should look like.

Our physical sample sealing rules are as follows:

• Retain 3 samples per production batch, not 1. A single sample is insufficient for comparison—it may have been scratched during transport or accidentally soiled by someone.
• Seal one immediately by attaching a sealing strip and recording the sealing date and batch number. Use one for routine comparisons, with access permitted. Keep the third as final evidence for disputes, without a sealing strip and without handling.
• The sample sealing card must contain six items: order number, batch number, material name + grammage + batch, machine and shift, sealing date, and operator. Only a complete record makes the sample traceable.
• The sample storage location must avoid exposure to light. Sunlight and ultraviolet radiation can cause many colors to shift noticeably within a few months, especially vivid spot colors and fluorescent colors. We place our sample cabinets toward the rear on the north side of the facility.

One further detail is worth noting: do not seal samples in bags. Transparent bags create reflections that obscure the color itself, and chemicals released by plastic bags can remain in prolonged contact with the sample and affect its color. The standard practice is to place a transparent acrylic cover over the sample, allowing ventilation while preventing direct contact and shielding it from light.

Archive Type 2: Color Cards and Measurement Data — Establishing the Expected Appearance Under Different Lighting Conditions

This is precisely what the home appliance customer’s experience taught us.

In color evaluation, “it looks right” is not a reproducible judgment. To handle color disputes objectively, three elements are required:

First: a physical color card. Print it on dedicated color-card stock—not ordinary paper—as part of the same production batch, number it in sequence, and archive it with the batch. Its purpose is to establish a reference for the normal color of this batch, allowing the color card and retained sample to be compared regardless of the customer’s lighting conditions.

Second: measurement data. Use a colorimeter (spectrophotometer) to measure the key color blocks of the batch in a standard light box, and record the L*a*b* values or corresponding ΔE values.

With this data, the dispute changes from “I think the color is wrong” to “the ΔE under your inspection conditions is 4.2, exceeding our agreed limit of 2.0.” The former can never be settled clearly, while the latter can resolve the case.

A colorimeter is not expensive—it costs a few thousand units—but its use must be standardized:

• Fix the measurement location—the same position on the cover or the center of the color block, with no changes in location;
• Fix the light source—use a D50 or D65 standard light box, not workshop ceiling lights;
• Record the ambient temperature and humidity—changes in paper moisture content affect measurements; without temperature and humidity data, the results are not comparable;
• Measure at least 3 points per batch and report the average, because single-point data can be distorted by the paper’s own unevenness.

Third: written agreement on lighting conditions. This provision is intended for the customer, but the printer must state it clearly on the approval form: our inspection and observation conditions are a D65 standard light box, 5000K cool-white workshop lighting, and natural daylight. The customer should also have approved the color under these three conditions.

In many actual color disputes, the customer views the product under warm office lighting and believes it is too yellow. Meanwhile, our retained sample has a color difference of 0.8 in a standard light box and is fully compliant. Writing the observation conditions into the contract substantially reduces the likelihood of disputes, because both parties know from the outset under which conditions the comparison will be made.

Archive Type 3: Proof Photos and Process Records — Establishing When a Decision Was Made

This type of archive is most often treated as unnecessary. In reality, it is the only way to resolve communication gaps.

A typical dispute scenario unfolds as follows:

A customer’s product manager approves a proof. The marketing department then assigns a new contact person. The new contact sees the proof photo and says, “The color does not look quite right,” although they have not viewed the physical proof. What they saw was the photo we sent via WeChat.

What was that WeChat photo? It was taken casually with a mobile phone in the workshop, under incorrect lighting, at an incorrect angle, and with an inaccurate white balance.

The dispute then becomes, “The photo you sent us was already yellow.”

Proof photos must therefore be taken according to a standardized procedure:

Process records are a separate matter: document the timing and basis of key decisions.

Our factory retains the following records:

• Prepress confirmation records—a scan of the customer-approved proof, the time of signature, and the version approved at that time;
• Material substitution records—if the paper or ink batch was changed before production, record the reason and whether the customer was informed;
• Press parameter records—ink volume, density curves, and drying or curing settings. This information is usually available in machine logs, which we export and archive;
• Environmental records—the temperature and humidity on the production day. This can be decisive in a dispute: if humidity was particularly high that day, paper moisture content increased and the same ink film genuinely produced a color shift.

Together, these four types of records answer the same question: what changed between the customer’s signature and shipment, and were those changes recorded? The party with records always has the advantage in a dispute.

How to Use the Three Types of Archives Effectively

Finally, implementation matters. If record-keeping is treated only as an archiving task, nobody will maintain it after 3 months. Our factory has integrated it into three actions attached to three points in the workflow:

Action 1: At proof approval, produce a complete set comprising a sealed physical sample, a color card, and a standard-light-source photo. These are not produced separately but completed in one operation. Each addresses a different question: which version was used for printing (the physical sample), what color qualifies as acceptable (the color card and data), and what the customer saw (the photo).

Action 2: When production starts, create a first-article sealed sample, first-article measurements, and first-article photos. A first article refers to the first few items produced after the press starts. Any mismatch with the customer-approved proof can be identified immediately—the only point at which the problem can be stopped before shipment.

Action 3: Before shipment, retain the last article and prepare a batch summary sheet. Together, the last-article and first-article samples provide evidence of color drift within the batch. Color drift does occur, but distinguishing normal drift from abnormal drift depends on these two endpoints and the intermediate measurements.

The completeness rate of the three-part archive is a quantifiable metric: our factory requires an archive completeness rate of at least 95% for all batches shipped each month. The remaining 5% are usually rush orders added by customers at short notice, when operators do not have enough time. We still complete these records, but we flag them in the system because they carry a higher risk of disputes.

To put it plainly: the main cost of these archives is that operators spend an additional 5 minutes after startup, take 2 additional photos, and make 3 additional measurements. In return, when a dispute arises, you have a complete set of mutually corroborating records—not an isolated retained sample and a statement that “we printed it correctly.”

Further Reading

• 3 Practical Boundaries of ΔE Color-Difference Control in Digital Printing: ICC profile / Media White / Postpress Lamination—an explanation of the principles of color-difference control and how to minimize color differences at the source
• What ΔE Color Difference Is Acceptable for Printed Products? Factory Constraints Behind 3 Judgment Criteria—how to establish an acceptable ΔE limit
• 3 Confirmation Processes for Custom Gift Boxes: First-Article E-Proof / First-Article Paper Proof / Sealed Sample—a detailed breakdown of how first-article confirmation should be written into a contract
• Digital Printing “100 Colors on 1 Sheet”: A Real Cost Breakdown of 5-Step Gradient Simulation for Pantone 1655—how to achieve accurate color management
• 4 Practical Pitfalls in the Gift Box Customer Acceptance “7-Day Reinspection Period”—archives and acceptance periods work together to create a complete process