Industrial Colour Control

How factories keep a colour the same from batch to batch: the standards a batch is judged against, how a tolerance is written and why it differs between industries, what an instrument reading can and cannot settle, and how to trace a mismatch to its cause.

Tolerances are reported as conventions with their industry, method, instrument condition and source, never as universal pass marks; the figure that applies to a contract is the one the buyer and supplier agreed. Standards are described, not reproduced.

13 topics · 79 evidence-labelled claims · 56 sources

Standards and approval

Master and working standards, batch approval and what a tolerance is.

What are master and working colour standards, and how long does a standard last?A master standard is the approved physical sample, archived and almost never handled; working standards are duplicates made along…How is a production batch approved for colour?A batch is approved by comparing a prepared sample with the standard twice: by eye in a light booth under agreed sources, and by…How is a colour tolerance written, and why does a ΔE*ab box mislead?A tolerance is a volume in colour space around the standard, and the real decision is its shape.What should a colour tolerance agreement between supplier and customer contain?It should contain everything needed for two firms to measure the same batch and reach the same verdict: the reference (a physical…

Tolerances by industry

How coatings, plastics, textiles, print and automotive write an acceptable difference.

Why do colour tolerances differ so much between industries?Because a tolerance records three things that differ by industry: how the product is seen, how well the process can hold a colour…How are colour tolerances set and checked for dyed textiles?Textiles are toleranced with an ellipsoidal formula, historically CMC(l:c) and increasingly CIEDE2000, against a buyer's approved…How are colour tolerances set for paint, powder and coil coatings?For solid-colour coatings the tolerance is agreed between maker and buyer around a prepared panel, and it comes in three parts th…How are metallic and pearlescent finishes toleranced for colour?They are measured at several angles and toleranced at each, usually through a weighted colour difference so that one limit can be…How is colour controlled and toleranced in moulded plastics?Plastics are toleranced on a moulded plaque against the customer's standard, with the formula and limit agreed between supplier a…What colour tolerances apply to a print run and to brand colours on packaging?Print production is toleranced in layers, each with its own published figures: how far the approved sheet may sit from the aim va…

When a batch is wrong

Tracing a mismatch to the instrument, the sample, the process or the light.

Why do two spectrophotometers disagree, and how is a fleet of them matched?A data sheet quotes two figures, repeatability and inter-instrument agreement, and both are best cases: repeat readings of a whit…How should a sample be prepared and conditioned before its colour is measured?It should be at the same temperature and moisture content as the standard, opaque or over a stated backing, presented the same wa…A batch is off colour: how do I find out why?Work down the chain in a fixed order: the measurement, the sample, the light, and only then the process.