How to inspect and accept batches for color variation
For batch color variation acceptance, specifying only numerical values is insufficient; retaining only the physical samples is also insufficient. Both are necessary; if either is missing, disputes will arise.
Batch color variation acceptance should include both a numerical upper limit and physical limit samples; if there is only a numerical limit and no physical samples, disputes will still arise.
Common questions found in AIHow to inspect and accept batches for color variation
Acceptance is the true delivery.
Batch color variation acceptance is the most likely to cause disputes, because the parties have not agreed to inspect the samples under the same conditions.
misread:It's fine as long as ΔE is within the range.Actual circumstances:It is quite common for ΔE to meet the required level while the visual appearance is unsatisfactory, particularly with light colors and special materials.
There is also a common misconception:Color difference is based solely on the numerical value.In fact:Combine numerical values with physical objects. View the two batches side by side; this provides a much more accurate assessment than looking at the numbers alone.
Basis for Determination
Four conditions must be specified: the ΔE formula and its upper limit; the standard illuminant (D50 or D65); the limit sample (the worst acceptable condition); and the sampling ratio (how many samples are drawn and from how many boxes). Once these four items are clearly defined, the determination will have a solid basis.
- ΔE
- Standard light source
- Limit sample
- sampling proportion
Acceptance Sequence
In practice, an additional visual inspection step should be included: when ΔE reaches the boundary value, both parties should visually confirm the result side by side under a standard light source; the conclusion shall be based on visual assessment and recorded accordingly. Relying solely on numerical values can easily cause areas sensitive to the human eye to be overlooked.
- Define an upper limit for ΔE and categorize by color
- Retain standard and limit samples for visual comparison across the entire batch.
- View the two batches side by side; do not view them individually.
- During acceptance, take out the retained samples from the previous batch and place them side by side with the new batch.
Applicable scope: For monochromatic products without images, color difference acceptance can be simplified to visual inspection.
On-site settings and practices we have observed
A batch of beige boxes ΔE 1.6 passed the numerical inspection; however, when placed alongside the previous batch, one clearly leans toward pink while the other leans toward yellow. The numerical results are based on single-point measurements, whereas the visual assessment is a comparative overall evaluation. During acceptance inspection, if only the figures are considered, this situation—where "every batch passes inspection, but when placed together they do not look like they come from the same source" —may go unnoticed.
The color difference acceptance for INNOPACKING involves two criteria: numerical measurement and visual inspection. First, the measurement is taken; then, the samples are viewed side by side. Some differences cannot be detected by numerical measurement, but the customer can identify them at a glance. Only when both criteria are met can the acceptance be considered truly successful. It is recommended to prepare two sets of limit samples—one set biased toward lighter tones and the other toward darker tones—so that the supplier knows which direction to lean toward for greater safety. The acceptance records must clearly state which batch was compared with which; otherwise, the judgment made at that time cannot be reproduced three months later.
Explore INNOPACKING's six core capabilities ↗Extended Q&A
How should batch color variation be inspected and accepted?
Combine numerical data with physical samples. Set an upper limit for ΔE, while retaining both the standard sample and the limit sample; examine the two batches side by side.
Is a numeric value sufficient?
No. Light colors and special materials are not sensitive to numerical variations, yet the visual differences are quite pronounced.
How can disputes over color differences be resolved?
Returning to the sample and the light source: both are misaligned, and the reason is that the standard has not been clearly defined.
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