Draft — architecture demonstration. Not yet reviewed as Handbook knowledge.
Test
Cap retention over ten minutes
A repeatable bar-side protocol for observing how long a foam holds its surface, so a team can compare builds without laboratory equipment.
The question
How do we compare the stability of two builds honestly, using only what is behind the bar?
Revised 2026-08-17
Method
- 01Prepare both drinks to identical recipes, ice and glassware.
- 02Photograph each drink from the side at pour, then at one, five and ten minutes.
- 03Record the first appearance of visible large bubbles and of exposed liquid surface.
- 04Repeat three times, alternating which build is made first.
Conditions
- Glassware
- Identical, pre-chilled coupes
- Ambient
- Recorded at the start of each run
- Runs
- 3 per build, order alternated
What is recorded
- Recorded
- Time to first large bubbles
- Recorded
- Time to exposed surface
Conclusion
This protocol is designed to make differences visible and arguable, not to produce a stability figure. Results are valid for the builds and conditions of the run, in that bar, on that day.
What this does not prove
- Observation is visual and therefore partly subjective.
- Three runs cannot separate small differences from ordinary variation.
- Nothing here measures taste, aroma or mouthfeel.
Validated by
Validates
Measured by
About this Handbook
The Foam Handbook is published by FOAMY WHITES, who make a pasteurised liquid egg white for bars. We write about foam the way we would explain it across the bar — including where our product is not the answer.