How to Run a Test Comparing Accelerated Test Instruments: Webinar Recap

Q-Lab's technical team recently presented a webinar on How to Run a Test Comparing Accelerated Test Instruments. The goal of the presentation was to provide listeners with a clear approach on structuring a scientifically-valid comparison test between two different makes or models of laboratory instruments, by following a few important steps.

Step 1: Match Test Parameters

The presentation began by talking about the importance of running the same test in every tester. Each weathering test program has a series of key test parameters to follow - some may be easy to identify, while others may be more subtle. A few of the test parameters that were mentioned included:

• Light spectrum
• Temperature
• Moisture / electrolyte
• Test cycle programming
• Any other subtle or unique test standard detail - there are LOTS of these!

A series of examples showcased the importance of matching test parameters, and how failing to do so can create inconsistent results within your testing program.

Step 2: Match Evaluation Procedures

In the second step, the group talked through the two types of evaluations: visual and instrumental. A previously recorded webinar presented by Q-Lab's Testing Services team goes in-depth on the best practices for evaluations to eliminate them as a source of variability.

Step 3: Establish Acceptance Criteria

Defining clear acceptance criteria and correlations goal for your comparison test is beforehand prevents any confusion once the test concludes. The team emphasized the importance of setting up your data collection program so that it is statistically significant, using two main guidelines:

1. Replicates, replicates, replicates
   • Expose enough specimens for at least three evaluations. More specimens is always better.
2. Multiple testers
   • Use at least three reference chambers when possible; a single test in a single tester is less likely to be valid.

Comparison testing between chambers requires one to set realistic expectations, based on the known performance of accelerated weathering and corrosion test chambers.

Step 4:  Implement Good Lab Practices

While exercising good lab practices should be standard practice, it's important to review and reinforce them when preparing to perform a comparison test.

1.  Consistency in lab practices
   • Your test chamber is only one source of variability, along with manufacturing, specimen preparation, conditioning & storage, handling, and laboratory personnel. All of these can cause variability in your results!
2. Follow guidance from test standards
   • Test standards such as ASTM E691 Standard Practice for Conducting an Interlaboratory Study (ILS) to Determine the Precision of a Test Method are good to reference when conducting tests
3. Utilize reference materials
   • Standard reference materials like blue wool and polystyrene, and known control materials, provide a helpful benchmark when conducting comparison testing

Comparing new test instruments to existing ones is a reasonable and common expectation when purchasing new lab equipment. The guidelines above help ensure that the comparison is performed fairly and that a clear outcome is reached.

Want to see more accelerated weathering and corrosion content? Access our full list of previously recorded webinars at Q‑Lab.com/Webinars.