Plastic plain cap, 18/410, black

Plain plastic cap 18/410 is a simple screw-on closure for bottles with an 18/410 neck finish. It seals smaller containers used for serums, facial and hair oils, tinctures, roll-on blends or cosmetic samples. The black colour is neutral and pairs well with amber, blue, frosted and clear glass, giving the finished product a consistent look regardless of bottle colour.

The cap is made from polypropylene (PP) and features an inner expanded polyethylene (EPE) foam liner. The liner presses against the bottle neck once tightened, preventing leaks during transport or horizontal storage. This is a plain closure with no dispensing element – contents are poured or dropped directly through the neck.

Why choose this cap

• Leak resistance – the EPE foam liner conforms to the neck and seals it even with light tightening, which is particularly important for oily and alcohol-based contents that tend to seep through.
• Easy handling – a smooth screw closure with no mechanical parts opens and closes effortlessly, does not jam and requires no adjustment.
• Proven material – polypropylene is a standard packaging plastic for cosmetics; we recommend testing compatibility with your specific formulation before a larger production run.
• Neutral appearance – the black colour draws no attention, letting the label and bottle colour define the product's look rather than the cap.
• Low weight – the cap adds virtually no weight to the packaging, which matters when shipping a larger number of samples or small-volume products.

Which bottles does it fit

The cap fits any container with an 18/410 neck finish, including small glass and plastic bottles. Typical applications include dropper bottles and vials for serums, facial oils, oil samples, tinctures and concentrates. Bottles with the same neck type as well as ready-made bottle-and-cap combinations are available in the Handymade range; when pairing your own components, we recommend verifying the seal with your specific formulation.

The cap is often used as a transit closure on bottles that are later sold with a dropper or spray. It seals the contents during storage and shipping, and the customer fits the dispensing element themselves upon delivery. It is equally suitable for samples and testers, where a dropper is unnecessary and a plain cap is a cheaper and more practical solution.

Useful information

Before first use on a cosmetic product, we recommend washing and sanitising the cap with isopropyl alcohol or ethanol, then allowing it to dry completely. Because the EPE liner is foam, let it air out thoroughly after sanitising so that no residual alcohol remains.

The cap can be reused provided the liner is not damaged or deformed. Prolonged contact with concentrated essential oils or strong solvents may cause the foam liner to soften or change shape. With such contents, inspect the liner after each opening and replace the cap at the first sign of deterioration.

The cap is designed to be tightened by hand – fasten it firmly but not forcefully. Over-tightening unnecessarily compresses the liner, accelerates wear with repeated opening and does not improve the seal. The packaging is suitable for use with cosmetic products and meets the applicable regulatory requirements; the declaration of conformity is available on the product page.

Polypropylene is a recyclable plastic. Due to the small size, we recommend handing the cap in for recycling together with other plastic packaging.

Frequently asked questions