A GLS bulb or ‘General Lighting Service’ bulb is essentially the classic general-purpose household and industrial lamp, which hasn’t changed much in shape since it first materialised in Victorian times. In the last two or three decades, many types of GLS bulb have become available: incandescent, energy-saving halogen, low-energy fluorescent, and LED.
In recent years the incandescent GLS bulb has been largely phased out of production by EU legislation, in favour of more energy-efficient alternatives. However, a diverse range of incandescent GLS bulbs is still available, including decorative filament bulbs, rough-service reinforced bulbs, daylight bulbs, and coloured bulbs.
Incandescent GLS bulbs are massively inferior to LED or CFL when it comes to energy-efficiency and lifespan, but they have advantages, nonetheless:
- Confined in colour by the laws of physics, incandescent bulbs are extremely consistent in their hue - LED or fluorescent bulbs are more prone to green/magenta variation.
- Their cosy colour temperature ranging from around 2000K to 2700K is perfect for creating a relaxing ambience in home or hospitality environments.
- Incandescent colour rendering is second only to halogen - its close relation - with both technologies scoring a maximum CRI 100 in any unmodified bulb.
- Incandescent technology is still the cheapest light source around, with energy-saving halogen being the nearest affordable equivalent.
Rough service bulbs
Rough service bulbs are usually constructed with reinforced glass and stronger filaments, thereby offering a longer lifespan than regular GLS bulbs. They can be legitimately sold by lighting retailers for industrial use, and are available in a wide range of wattages.
Decorative filament GLS bulbs
Borrowing from century-old designs, decorative filament incandescent GLS bulbs use a carbon or drawn tungsten filament (usually the latter) to create a near-mesmerising warm glow of light. Usually their colour temperature is around 2000K.
The filaments are shaped attractively to enhance appeal. These bulbs can create a wonderfully relaxing ambience when displayed well. They’re a great choice for fine-dining restaurants, hotels, or the home.
To counteract the inherent warm colour temperature of an incandescent bulb, daylight bulbs are coated in blue. This effectively converts their output to a daylight balanced kelvin temperature of approximately 6000K to 6500K.
Daylight bulbs are typically used for fine-detail crafts and hobbies such as reading, drawing, or needlecraft. Their natural output helps to reduce eyestrain and headaches, and is also an aid to concentration. What are daylight bulbs takes a more in-depth look at this type of bulb.
Coloured incandescent GLS bulbs are useful for displays, and can be used to create a festoon for many types of celebration and event. In conjunction with weather-resistant lamp holders they can be used outside.