Level 8: Performance Engineering and Evaluation
Projection, longevity, bloom, intensity and stability, and how to test them without fooling yourself.
Lessons
What performance means
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Projection, Sillage and Diffusion: Measuring the Unmeasurable
These words describe how far a fragrance reaches and they are hard to measure. Learn clear definitions and a repeatable distance test with its limits stated.
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Longevity and Tenacity: Study Guide
Read our guide to tenacity on a blotter, then run a tenacity log on ten materials over a month and compare what you find with what the suppliers state.
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Bloom: How a Fragrance Opens Up
Bloom describes how a fragrance fills space as it warms or evaporates. Learn the term's uses, how it differs by product, and a simple controlled comparison.
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Odor Intensity: Rating Strength Reliably
How perceived strength grows with concentration, why a doubling is not twice as strong, and how to build a rating scale with references you can trust.
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Fixatives: Study Guide and a Test of the Claim
Read our guide to fixatives, then test one claim yourself: does this material actually make a citrus last longer, or does it just add a smell of its own?
Testing with controls
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Design a Wear Test: Study Guide
Read our longevity and sillage guide, then write a full wear test protocol on paper, including the safety review that must happen before anyone wears a sample.
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Comparative Evaluation: Choosing the Right Test
Triangle, paired, ranking, duo-trio or descriptive? Choose the test that answers your question, understand chance levels and avoid asking the wrong thing.
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Evaluation Bias: How You Fool Yourself
Expectation, order, fatigue, color and the wish to succeed all change what you smell. Learn the main biases in evaluation and simple ways to reduce them.
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Consumer Testing: Study Guide
Read our consumer testing guide, then draft a small questionnaire and critique it for leading questions, poor scales and the wrong people before you use it.
Stability
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Stability Testing: Study Guide and Study Design
Read our stability testing guide, then design a real study for one of your formulas: conditions, controls, checkpoints, and what would count as a failure.
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Antioxidants and UV Absorbers: Study Guide
Read our guide to perfume stabilizers, then decide on paper whether one of your formulas needs one, what else might solve it, and what you must check.
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Interpreting a Failed Stability Test
A failed stability test is a diagnostic puzzle. Learn to read which conditions failed, narrow the suspects, retest one change, and decide what must change.
Substrates
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Carrier Effects: What the Solvent Does to a Fragrance
One concentrate behaves differently in alcohol, oil or a water-based carrier. Compare them, understand why, and adjust the formula rather than just swapping.
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Skin Interactions: What We Know and What We Don't
Why might a fragrance differ between wearers? Temperature, skin care and perception all play a part. Learn what the evidence supports and how to test fairly.
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Fabric Interactions: A Controlled Test
Fabric holds fragrance differently depending on fiber, and may stain. Design a controlled test across cotton, wool and synthetics, with results you can trust.
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Adapting to a Product Base: Level 8 Project
Read our guide to adapting fragrance for products, then complete the Level 8 project: a controlled performance study on one formula, with honest limits.