SESH FRAGRANCE ACADEMY | ADVANCED
Are all plastics bad and all glass containers automatically suitable?
Oxidation, packaging and ingredient stability — a published visual reference for the topic, not SESH product-test data.
Open full-size image ↗Identify every contact component and design evidence-based compatibility, leak and migration checks.
The bottle is only one part of the pack
The formula may contact the bottle body, dip tube, pump internals, elastomeric seals, closure liner and sometimes coatings or adhesives. A largely inert glass wall does not guarantee compatibility of the complete dispensing system. Ingredients may sorb into, swell or alter components, and seals may leak. Begin with a cross-section map listing each material that might contact liquid or vapor.
Glass is a useful barrier, not a complete safety certificate
Glass is often an excellent barrier and can be compatible with many perfume liquids, but it is breakable and may carry coatings or decorative treatments. Clear glass transmits light, potentially affecting light-sensitive formulations. Closure and pump compatibility remain separate from the bottle wall. Select and validate a complete pack system, not simply a material label.
Oil droplets dispersed in water: a real emulsion example, not a photograph of a SESH formula or proof of cream efficacy.
Open full-size image ↗PET, HDPE and other polymers behave differently
PET, HDPE and other polymers differ in permeability, sorption and chemical resistance, which also depend on grade, additives, wall thickness and contact time. A specified fragrance system may work in a verified polymer pack, while another causes extraction, odor drift or loss. Both 'all plastics react with alcohol' and 'PET is universally safe for perfume' are unjustified. Request suitability data for the actual formulation.
Sorption versus extractables and leachables
Sorption refers to fragrance constituents entering or binding to packaging material, potentially changing the liquid's composition. Leachables migrate from pack components into product under actual use, while extractables are identified under specified laboratory extraction conditions. A missing citrus facet could be due to sorption, volatile loss or chemical change. The test should discriminate between these mechanisms rather than label every drift 'spoilage'.
Seals and pumps are failure points
An unsuitable elastomer seal may swell or lose sealing force, dip tubing may change color or stiffness, and poor closure integrity can allow leakage or volatile loss. A bottle losing fill may have a dispensing or closure issue rather than a damaged base. Inspect sealing, leak rate, mass change, odor drift and component condition over time. Elastomer names alone are not certificates of suitability.
Orientation and transport stress matter
Useful pack qualification includes upright and relevant non-upright storage, leak checks, mechanical or transport stress and justified temperature conditions. Passing while upright does not prevent failure during distribution. Flammable fragrance liquids must be evaluated using qualified safe testing procedures, not improvised high-pressure or heating tests at home.
A pack qualification matrix
Compare glass pack G and specified PET pack P using matched batches and known pump variants, changing one relevant element at a time where practical. Record mass loss, color, odor, seal integrity, leaks and spray quality at scheduled checkpoints. If bottle, seal and pump all change together, causal attribution becomes difficult. Approve each pack configuration against documented criteria.
Case study: one closure causes a failure
Hypothetical G1 has a compatible seal and passes leak tests; G2 uses the same glass but a different seal which swells and leaks. The suspect component is the closure system, not the glass wall. Verify seal specifications, repeat matched testing and hold the failing configuration pending investigation.
Practical exercise
Draw a fragrance package cross-section with bottle wall, gasket, dip tube, pump and cap. For each specify one possible failure mode and its verification test. Compare two imaginary packs without using retail price as a quality proxy.
Three visual concept maps
Anatomy of the complete pack
- Bottle body and barrier
- Dip tube and flow
- Gasket and seal
- Pump and atomizer
- Closure assembly
Different interaction mechanisms
- Sorption: ingredient uptake by pack
- Leaching: release into product
- Permeation: passage through pack
- Swelling: seal deformation
Pack qualification
- Same formula revision
- Known packaging components
- Leakage and mass loss
- Color, scent and function
- Orientation and transport trials
Scientific glossary
- Sorption
- Uptake or binding of a substance onto or within another material.
- Leachables
- Substances migrating from packaging into product under use conditions.
- Gasket
- Sealing component that helps prevent liquid or vapor leakage.
