RUŌOD Lab

Level 5 · Perfume Mathematics and Formula Design

Reproducibility Test: Weigh It Twice

Read our repeatable batches guide, then make one formula twice on separate days and test blind whether you can tell them apart. A plain test of your method.

Intermediate 15 min study By the RUŌOD Lab team Updated

In short

A repeatable formula is one you can make twice and get the same result. The reference guide covers the controls that make this possible. This study guide tests your own process directly, and the result will tell you whether to trust your own comparisons from here on.

What you will learn

  • Test your own reproducibility
  • Find the likely source of any difference between two batches

Before this lesson: Documenting a Formula: Study Guide

What to look for as you read

  • Which sources of variation the guide lists, and which apply to your bench.
  • How tolerances are set, using the tolerance guide.

Practical exercise: Weigh it twice, smell it blind

About 60 minutes · You will have: two batches of one formula, a weighing comparison and a blind test result

  1. Choose one documented accord. Make it from its record. Note each actual weight.
  2. Make it again on another day, without looking at the first batch.
  3. Compare the logs: largest proportional difference between the batches, on any line.
  4. After both have rested equally, run six blind triangle trials.
  5. Write what you conclude about how reliable your process is.

You have done this well if you state your largest weighing difference and your blind score, and you do not overstate what they mean. This completes the reproducibility requirement of the level project.

Knowledge check

1. Two batches differ. Which should you check first?
Show the answer

Weighing logs and which stocks and lots were used. The records usually reveal the difference, provided you kept them.

2. You cannot tell them apart in six triangle trials. What can you conclude?
Show the answer

That you found no perceptible difference in this test. Failing to find a difference is not proof of none, but it is a useful result.

3. Why make the batches on separate days?
Show the answer

To include the day-to-day variation you are trying to measure. Repeating immediately hides the effects of memory and routine.

Further reading and materials

Written and reviewed by the RUŌOD Lab team. This is general education, not legal, regulatory, medical or safety advice. Example dilutions and exercises are for learning, are not validated products, and have not been safety-assessed. Completing a lesson confers no qualification. How we check these lessons.