Blog

How E-Liquid Manufacturing Works: From R&D to Bottling

Modern e-liquid manufacturing facility with cleanroom environment and automated filling equipment

The 7-Step Manufacturing Process

Manufacturing e-liquids at a professional level is far more complex than simply mixing flavors into a base. It requires pharmaceutical-grade ingredients, cleanroom environments, precision equipment, and rigorous quality control at every stage. Here is how the process works from start to finish.

Step 1: Ingredient Sourcing

The foundation of every e-liquid is its base ingredients:

  • Propylene Glycol (PG) — USP/EP pharmaceutical grade, 99.5%+ purity. PG is classified as FDA GRAS (Generally Recognized as Safe) for food use. It provides throat hit and carries flavor effectively.
  • Vegetable Glycerine (VG) — USP/EP pharmaceutical grade, 99.5%+ purity. VG produces vapor density and adds sweetness.
  • PG and VG together make up 80-95% of the total e-liquid volume, depending on the recipe.
  • Nicotine — pharmaceutical-grade nicotine, sourced from certified suppliers with full chain-of-custody documentation.
  • Flavor concentrates — food-grade flavoring compounds, individually screened for inhalation safety and TPD compliance.

Every raw material batch arrives with a Certificate of Analysis (CoA) from the supplier, and is verified against specifications before being accepted into inventory.

Step 2: Recipe Formulation (R&D)

Recipe development is where science meets creativity. Flavor chemists develop formulations by:

  • Selecting and combining flavor concentrates to achieve a target taste profile
  • Determining the optimal PG/VG ratio for the intended device type (higher PG for mouth-to-lung, higher VG for direct-lung)
  • Calibrating nicotine strengths — typically 0, 3, 6, 12, 18, and 20 mg/mL for the EU market
  • Screening every ingredient against the TPD banned substances list (diacetyl, colorings, caffeine, taurine, CMR substances)
  • Conducting iterative taste testing and adjusting formulations

A single commercial recipe can go through dozens of iterations before it is approved for production.

Step 3: Mixing

Production mixing takes place in cleanroom environments using automated equipment:

  • Industrial-grade mixing tanks with precise temperature and speed controls
  • Automated dosing systems that measure ingredients to exact specifications
  • Batch sizes ranging from small pilot runs to large-scale production batches
  • Every batch is assigned a unique batch number at the point of mixing

Cleanroom environments minimize contamination risk. Workers follow strict hygiene protocols including gowning, gloving, and controlled access procedures.

Step 4: Steeping

Steeping is the maturation period after mixing, where the e-liquid develops its full flavor profile:

  • Freshly mixed liquids are stored under controlled conditions (temperature, light exposure)
  • The steeping period allows flavor molecules to fully integrate with the PG/VG base
  • Duration varies by recipe — some flavors reach maturity in days, others require weeks
  • Quality teams conduct taste checks at intervals to determine when the batch is ready

Not all recipes require extended steeping, but for complex multi-flavor profiles, this step is essential to achieving a consistent taste.

Step 5: Quality Control Testing

Before any batch moves to the filling line, it undergoes comprehensive laboratory testing:

  • HPLC (High-Performance Liquid Chromatography) — verifies nicotine concentration matches the labeled strength, and screens for aldehydes (formaldehyde, acetaldehyde, diacetyl, acetyl propionyl, acetone, acrolein)
  • ICP-MS (Inductively Coupled Plasma Mass Spectrometry) — tests for 10 heavy metals: copper, aluminium, nickel, iron, chromium, lead, arsenic, cadmium, mercury, and antimony
  • GC-MS (Gas Chromatography-Mass Spectrometry) — impurity screening for ethylene glycol, diethylene glycol, caffeine, ethanol, methanol, and 2-propanol

For a detailed breakdown of all required tests, see our Quality Control Testing guide.

Step 6: Filling and Bottling

Filling is performed with automated bottling lines:

  • Precision filling nozzles ensure exact volume in every bottle (10 mL TPD-compliant bottles for nicotine-containing liquids)
  • Child-resistant and tamper-evident closures are applied mechanically
  • Each bottle receives a label with: product name, ingredient list, nicotine content, batch number, production date, health warnings, and manufacturer details
  • Health warnings must cover at least 30% of the two largest surfaces of the packaging

Step 7: Final Inspection and Release

Before any batch leaves the facility:

  • A double-check system verifies that labels match contents, closures are properly sealed, and packaging meets all regulatory requirements
  • Batch documentation is completed and archived for full traceability — every bottle can be traced back to its specific batch number and production date
  • Retained samples from each batch are stored for reference and potential future testing

Quality Management Systems

Professional e-liquid manufacturing facilities operate under internationally recognized quality management systems:

ISO 9001:2015

ISO 9001:2015 is the international standard for quality management systems. Certification requires:

  • Documented processes for every stage of production
  • Regular internal audits and management reviews
  • Third-party certification audits every 3 years by accredited auditing bodies
  • Continuous improvement processes based on data and corrective actions

HACCP / GMP / GHP

In addition to ISO 9001, food-safety-aligned standards govern manufacturing hygiene:

  • HACCP (Hazard Analysis and Critical Control Points) — systematic identification and control of contamination risks
  • GMP (Good Manufacturing Practice) — standards for production environment, equipment, and processes
  • GHP (Good Hygiene Practice) — personnel hygiene, cleaning protocols, and pest control

Batch Traceability

Every finished product carries a batch number and production date on the bottle. This enables:

  • Full traceability from finished product back to raw material batches
  • Rapid identification and recall capability if any issue is detected
  • Compliance with TPD annual reporting requirements

References

First 5 Labs Manufacturing

First 5 Labs operates ISO 9001 and ISO 14001 certified manufacturing facilities in Zagreb, Croatia. From R&D and formulation to filling, testing, and TPD registration, we handle the entire production chain in-house. Learn about our manufacturing capabilities.

Manufacturing Quality ISO Production
Back to Blog