Aluminium cap, silver, 18 mm

An 18 mm aluminium cap seals a bottle securely wherever dispensing is not required. It is a screw cap without a dispensing opening for bottles and vials with an 18 mm neck. Inside, it has a foam polyethylene (EPE) sealing insert that, when tightened, seats against the rim of the neck and prevents the contents from leaking.

Suitable for contents that are simply poured or decanted from the bottle: tonics, hydrolats, facial and body oils, or samples. It also works as a storage and transport closure, with the dropper or spray fitting attached only before use. The cap is suitable for contact with cosmetic products.

When to use an aluminium cap

• Secure closure without dispensing – the contents are poured directly from the neck, making it suitable for thin to medium-viscosity liquids where measuring drops or doses is not required.
• Storing intermediates and bulk stock – a macerate or finished oil blend remains sealed until decanted into smaller containers.
• Samples and travel sizes – the cap has no moving parts that could be compressed or opened in a bag.
• Metallic appearance – the silver finish complements both clear and coloured glass, giving a consistent look across an entire product line.

How the cap seals

The seal is not provided by the metal itself, but by the foam insert. When tightened, it compresses and conforms to the rim of the neck. With a high proportion of essential oils or solvents, it is advisable to verify the insert's performance by testing with the specific formulation.

Bottles with the same neck type (specified in the product parameters) and ready-made bottle-and-closure combinations are available in the Handymade range.

What's worth knowing

The bottle should be filled to the nominal volume, not to the brim. The nominal volume is the quantity for which the container is designed under standard filling conditions. The total brim-full volume is the physical capacity up to the neck. The difference between the two is the headspace reserved for the closure and for the expansion of the contents with changes in temperature. If the bottle is filled to the brim, the contents will be forced into the thread when closing and the cap may not seat correctly.

Before first use, disinfect the cap and leave it to dry completely with the insert facing up. Moisture trapped under the insert can contaminate the contents, so the cap should only be fitted once it is dry.

Frequently asked questions