An Aerosol Goes Through Five Stages Before It Leaves the Plant
An aerosol is made in five stages: the concentrate is formulated, the can and valve are chosen, the container is filled and the propellant is injected, every unit is leak-tested in a hot water bath, and finally the product is labelled, batch-coded and palletised. No unit leaves the plant without passing all five.
Formulation Sets How the Aerosol Behaves
The concentrate is the liquid part of the aerosol: the active ingredients, the solvent that keeps them in solution and the additives that stabilise the mixture. Its composition decides how well the product works, but also less visible things: whether it corrodes the can, clogs the valve or changes with temperature.
That is why the formula is validated before production, including when the customer supplies it: viscosity, compatibility with the can and the behaviour of the mixture with the chosen propellant are all checked. In the plant, the concentrate is prepared in mixing tanks of 18,000 and 35,000 litres, so a full batch can be made in one go and kept homogeneous.
The Can and Valve Are Chosen with the Formula
The can, the valve and the actuator are decided together with the formula, never afterwards. Ilerspray fills aluminium or tinplate cans from 50 to 750 ml, and the material depends mainly on how the concentrate reacts with the metal and on the format the sales channel requires.
The valve controls the flow and the actuator defines the spray pattern: jet, mist or foam. Changing one of the three at the end of development usually means reviewing the other two.
💡 Technical tip: settle the valve type, the propellant and the actuator in the same meeting where you close the formula. If one changes at the end, the sample you approved no longer represents the product.
The Four Filling Operations
Filling is the stage where the aerosol becomes a pressurised container. It happens in line, in this order:
| Operation | What is done | What is checked |
|---|---|---|
| Can preparation | Empty cans are inspected | Dents, scratches or residue |
| Concentrate dosing | The exact quantity of product is filled | Weight per unit |
| Valve crimping | The valve is sealed onto the can | Tightness of the seal |
| Propellant injection | The gas enters under pressure through the valve | Final weight and pressure |
The propellant is the gas that pushes the product out. Ilerspray's plant works with liquefied petroleum gas (LPG), DME and CO₂, and the choice is made at formulation because it changes the output pressure and the spray type.
Leak Testing Closes the Line
Every filled unit goes through a hot water bath at 50 °C. The heat expands the gas and any micro-leak becomes visible; units that fail are removed before labelling. This is not optional: it is a requirement of the European rules on aerosol dispensers, implemented in Spain by Royal Decree 1381/2009.
For example every aerosol product must be tested in a hot water bath (50°C), or an approved equivalent alternative, to guarantee that the aerosol dispenser is sufficiently pressure-resistant and remains virtually hermetically sealed.
Weight control during filling is the first filter, and the water bath is the unit-by-unit confirmation.
Labelling, Batch Code and Pallet
The last stage gets the aerosol ready for market. The actuator and cap are fitted, the label is applied or a pre-lithographed can is used, and every unit receives the batch code required by law, which traces any can back to its production.
The aerosols are then packed into cases and palletised to the customer's logistics specifications, ready for dispatch from the Lleida plant.
If you want us to run this whole process for your product, our aerosol contract manufacturing page lists formats, propellants, capacities and the request form.
