Detection
Detection thresholds vary by substance, person and conditions.
Independent field notebook · New Delhi
The Olfactory
Notebook.
A curious human, a complicated nose, and an attempt to understand how invisible molecules become memories, emotions and perfumes.
Between biology, chemistry, perception and craft, there is a fascinating world worth smelling carefully.
By Sahil Tayal · Independent writing and experimentation, not a scientific journal or safety certification.
01 / Biology
What happens when we smell?
Smelling is not simply detecting a chemical. It is a biological process that becomes a perceptual experience inside a living brain.
Volatile molecules reach the olfactory epithelium high inside the nasal cavity. Some interact with receptors on sensory neurons, initiating signals that travel to the olfactory bulb and onward through networks involved in perception, learning, emotion and memory.
Odorants can interact with multiple receptor types, while receptors can respond to multiple odorants. The resulting patterns contribute to identification.
The experience is not a direct photograph of a molecule: prior learning, context and attention matter.
A simplified pathway
Volatile molecules
↓ Olfactory receptor neurons
↓ Olfactory bulb
↓ Distributed brain networks
Perception, association and memory
Teaching simplification; actual processing is distributed and recurrent.
Recognition
Recognising an odor is not identical to being able to name it.
Meaning
Experience and culture help shape whether a smell feels pleasant or familiar.
02 / Memory
Why can a smell take us somewhere?
Odor-cued autobiographical memory is a genuine topic of psychological and neuroscientific research. A scent can evoke a childhood kitchen, a rainy afternoon or a person not consciously recalled for years.
But not every smell creates a vivid memory, and a perfume cannot guarantee an emotional response. Learned associations, expectations and attention can influence what is recalled.
Observation: This scent reminds me of monsoon evenings.
Hypothesis: Repeated experiences helped establish the association.
Uncertainty: Which mechanisms and contextual cues explain this particular memory?
Hypothesis: Repeated experiences helped establish the association.
Uncertainty: Which mechanisms and contextual cues explain this particular memory?
03 / Materials
Molecules, accords and notes
Perfume is both a material formulation and a language for describing what it smells like. These are related, but not identical.
Aroma molecules
Individual chemicals have odor properties affected by concentration, mixtures and individual sensitivity.
Accords
Combinations of materials create recognisable impressions that may be more complex than their components.
Fragrance notes
Rose, amber, leather or sea breeze are descriptive conventions, not literal ingredient declarations.
Natural does not automatically mean safe
Natural extracts can be complex mixtures. Synthetic aroma chemicals can be individual substances or mixtures. Either can irritate or sensitise; identity, composition, concentration and exposure determine relevant hazards.
04 / Time
Why perfume changes on skin
Opening
More readily evaporating components may dominate early impressions.
Development
As the composition above a fragrance changes, different facets become noticeable.
Dry-down
Some materials remain perceptible longer, depending on formulation and conditions.
The top-heart-base pyramid is a useful description, not a rigid physical law. Materials overlap in evaporation and perception. Higher concentrate percentage does not necessarily guarantee greater projection or perceived longevity.
Fixation is not magic
Fixatives may influence evaporation or perceived persistence, but there is no single universal mechanism. Longevity and aesthetic quality are different questions.
05 / Tool
Dilution calculator
Calculate nominal concentrate and diluent volumes. This is arithmetic, not a formulation safety assessment.
Concentrate
10 mL
Diluent
90 mL
100 mL × 10% = 10 mL concentrate.
Arithmetic only. Assumes nominal additive volumes; actual mixtures may contract or expand. No evaluation of density, IFRA restrictions, sensitisation, compatibility or legal compliance. Mass-based formulation may be more appropriate for precision.
06 / Documentation
Keep a better scent notebook
Record quantities, sources, conditions and observations. A subjective observation is useful when honestly labelled as subjective.
Reproducibility matters
Give each formula a unique identifier. Document material sources and lots, measurement method, storage conditions and application amounts. Separate blotter observations from skin observations, and record negative results too.
The curious monkey principle 🐒
If a perfume smells magnificent at 9 AM, ordinary at noon and mysterious at 5 PM, record all three. The notebook is there to discover what happened, not to prove success.
Blank experiment log
OLFACTORY EXPERIMENT LOG Formula ID: Date: Objective: BATCH Target batch size: Actual batch size: Concentration (% and basis): Concentrate quantity: Diluent quantity and identity: Measurement method (mass/volume): MATERIALS (repeat per material) Name: Supplier/source: Lot reference: Documented dilution: Quantity: Safety documentation reviewed: PREPARATION Mixing procedure: Container: Storage conditions: Observations: BLOTTER Application amount: 0 min: 15 min: 1 hour: 4 hours: 24 hours (if applicable): SKIN (only if separately assessed as appropriate) Application location and amount: 0 min: 15 min: 1 hour: 4 hours: 8 hours (if applicable): CONDITIONS Temperature/environment: Other fragrances present: Evaluator: Confounders: SAFETY Hazards identified: Restrictions to verify: Documentation checked: Skin exposure decision: Adverse reactions/incidents: INTERPRETATION Observed characteristics: Comparison with previous version: Hypotheses: Uncertainties: Next experiment:
No account, tracking or server submission.
07 / Safety
Safety belongs inside the experiment
Pleasant smell does not establish safe inhalation or skin application. Irritation and allergic contact sensitisation are different. Prior tolerance does not guarantee future tolerance.
A casual skin patch test cannot establish safety. Clinical patch testing for suspected allergies belongs with qualified healthcare professionals. Before intended skin use or distribution, check supplier safety documentation, applicable IFRA Standards, product category, exposure and local legal requirements. IFRA conformity does not itself establish compliance with every law.
Store and label materials appropriately, consider ventilation and flammability, and keep them away from children and pets.
Educational only. No toxicological clearance, exposure limits or regulatory certification are supplied here.
08 / FAQ
Questions worth asking
Are perfume notes actual ingredients?
Not necessarily. Notes describe perceived impressions; a jasmine note does not prove natural jasmine extract is present.
Does a higher concentration always last longer?
No. Composition, volatility, application, environment and perception all influence apparent longevity.
Why do people smell the same perfume differently?
Sensitivity, receptor genetics, experience, attention and context can contribute.
Is natural fragrance safer?
Neither natural nor synthetic origin establishes safety. Assess actual materials and exposure.
Can perfume change mood?
Odors may influence experience through emotion, expectation and association. They are not established treatments for mental health conditions.
Does this calculator tell me what's safe for skin?
No. It performs volume arithmetic only.
Why does my perfume seem to disappear?
Olfactory adaptation and attention can reduce awareness; physical evaporation may also be occurring.
09 / About
An experiment in curiosity
I'm Sahil Tayal, an independent writer and interdisciplinary practitioner based in New Delhi. My background includes an MBA from Jamnalal Bajaj Institute of Management Studies (JBIMS), experience with organisational behaviour and family retail, and experimental perfumery.
Olfaction sits at an intriguing intersection: chemistry meets biology, biology meets memory, and memory meets the stories we tell about ourselves.
Editorial standards
Distinguish findings from observations, label hypotheses, avoid invented citations and credentials, and revise explanations when better evidence emerges. This is an independent educational project, not a peer-reviewed journal or institutional publication.
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