Why are pharmaceutical bottles brown?
Pharmaceutical bottles are brown, or more precisely amber, because the coloured glass absorbs a large part of ultraviolet and short-wavelength visible light, which can break down light-sensitive ingredients. Amber glass does not make a product last forever, but it slows photodegradation and so helps keep the contents closer to their intended quality for longer.
How amber glass protects the contents
Many active substances, essential oils, vitamins and plant extracts react when exposed to light. Ultraviolet radiation and blue light carry enough energy to start chemical changes such as oxidation, discolouration or loss of strength. Amber glass is coloured by adding iron and sulphur compounds during melting, which gives it strong absorption in the range below roughly 450 nm. Clear glass lets nearly all of that light through, while green glass and blue glass offer only partial protection.
The effect is limited to light. Amber glass does not stop oxygen, heat or moisture, so the closure, the storage temperature and the formulation still matter.
Amber compared with other glass colours
| Glass colour | Light protection | Typical use |
|---|---|---|
| Amber | High against UV and blue light | Medicines, tinctures, essential oils, supplements |
| Cobalt blue | Moderate, mostly cosmetic appeal | Some cosmetics and skincare |
| Green | Some UV protection | Beverages, certain oils |
| Clear | Little or none | Products that are not light-sensitive |
Why the colour is brown rather than another shade
Historically, amber glass was found to give the best protection at reasonable cost, using widely available raw materials. Pharmacopoeias and regulatory guidance treat light-resistant containers as a standard way to protect sensitive preparations, and amber glass is the most familiar form. Its colour has also become a signal to consumers that the product inside is a pharmaceutical, nutritional or other serious product.
Does a product always need amber glass?
No. If a formulation is stable under light, clear or coloured glass may be perfectly adequate. Some brands choose clear glass for the look of the product, relying on an outer carton for protection. Stability testing of the finished product in its final packaging is the reliable way to decide. A manufacturer who wants to claim a shelf life should base that on such tests rather than on the colour of the container alone.
Storage tips for users
- Keep the bottle closed and upright when it is not in use.
- Store it away from direct sunlight and from sources of heat.
- Leave the bottle in its carton if the label recommends it.
- Follow the storage conditions and date on the label.
Light, stability and shelf life
Photodegradation is only one of several ways a product can change over time. Oxygen from the headspace, temperature swings and contact with the closure materials all play a part. For this reason formulators usually combine amber glass with a well-fitting closure and sensible storage advice. Because amber glass absorbs light rather than reflecting it, a bottle left in direct sun can still warm up, so a shelf away from windows is a better place than a sunny windowsill. The colour is a useful first line of defence, but it works best as one part of a complete packaging and storage plan.
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Is brown glass the same as amber glass?
In packaging the two terms are used for the same product. The tone can vary slightly from light honey to deep brown depending on the batch and the thickness of the glass.
Does amber glass block all light?
No. It blocks most ultraviolet and blue light, but some longer visible wavelengths pass through. It significantly reduces exposure, not eliminates it.
Is plastic amber as good as amber glass?
Coloured plastics can also filter light, but glass is chemically inert and is a better barrier against gases and moisture. The right choice depends on the product.
Choosing droppers for your product
If your liquid is sensitive to light, an amber dropper bottle is a sensible default. Packaging.si supplies amber glass DIN18 bottles from 5 to 100 ml and matching droppers with glass pipettes.
