Professional Detailing2 min read

Composite Samples in Coating Testing: Averaging Can Hide Local Differences

Combining material from several containers into one test sample changes the question being answered. A composite can describe the combined material while concealing differences between individual containers or locations.

Updated · NANOLAB Knowledge

The key distinction

The sampling plan should state whether the goal is a lot-level assessment, investigation of variation or diagnosis of a specific container. The laboratory or supplier should approve the collection method. Combining samples for convenience should not silently replace a plan intended to identify local problems.

Practical checks

  1. Define the decision and the unit being evaluated.
  2. Ask whether individual or composite samples are appropriate.
  3. Preserve the source identities and proportions used in any approved composite.

Example

Illustrative example: one container has an unusual appearance while others look normal. Mixing samples from all containers may dilute evidence of the unusual one. An investigation focused on that container needs a sampling approach that preserves the difference instead of averaging it away.

Scope and limits

Do not mix coating products or batches without explicit technical authorization. This guide describes a sampling distinction, not a preparation instruction. A composite result cannot automatically be assigned to every source container, and a passing combined sample does not prove the absence of individual variation.

Related guidance

Ask NANOLAB about the exact product and intended use. Use the current product documentation for formulation-specific instructions.