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At GoodBulb, we strive to improve your lighting know-how. Through blogs, presentations and one-on-one consultations, GoodBulb aims to help you not only understand how lighting works, but how to chose the best bulbs for your lifestyle. We provide the knowledge to empower you to light your world.

‘A’ is for Arbitrary

What puts the ‘A’ in A-bulbs?

Before we begin, let’s get one thing straight: A-shaped bulbs do not actually look like the letter ‘A’. Except, maybe, neon tubes that actually are shaped like that. But that’s a story for another day. Whew, glad we got that cleared up! 

So, that said, what exactly is an A-shaped light bulb? I’m so glad you asked! Most people, when they think of a light bulb, likely imagine a typical tear drop shaped bulb the likes of which have been globally recognized since the late 1800s. The standard A19 light bulb, as made famous by Thomas Edison, oh, so long ago . What many people don’t understand about these bulbs, though, is what in the heck A19 even means (and why they should care). Well, let me shed some light on that for you! 

See what I did there? Shed some ‘light’…? Yeah? Ok, ok, I know. Keep reading.

In addition to the A19 shape mentioned, we are familiar with A21, A23, and A15 shapes as well. The ‘A’ in these bulb codes stands for ‘arbitrary’, and in the case of light bulbs we take the definition of that to mean the shape was decided upon based on random choice of its designer. So, thanks for that Mr. Edison! The number that follows the ‘A’ designation indicates the bulb’s size when measured in ⅛” increments. 

For example, a standard A19 bulb diameter measures at 19/8”, or when converted is 2.375”. An A21 bulb measures at 21/8”, or 2.625” in diameter. Keep in mind, though, that the A21 bulb is generally slightly longer than the A19 which may prevent it from properly fitting into some fixtures. Be mindful of this factor when selecting a replacement bulb for your application, since not all A-shaped bulbs are interchangeable. 

The typical design of the A-shape light bulb has not changed much since the prototype was fabricated by Thomas Edison. Of course, there have been state-of-the-art enhancements to improve its functionality, since then. Such developments have focused mostly on the technologies that make light bulbs work, from the original incandescent versions to halogen and compact fluorescent models, all the way to the LEDs we’ve landed on today. However, through all the technological changes the ‘A’ bulb has been put through, its shape has remained pretty much the same. This is due to how recognizable that shape is, and to ensure that consumers will more easily digest the technology advances as they are rolled out. Or in other words, manufacturers of lighting products continue to produce new light bulbs modeled after Edison’s version so that everyone stays comfortable. 

An LED is vastly different in function and design to an incandescent. LED does not require a glass housing and a filament in order to work, where incandescent does. Ergo, when LED lighting was introduced, an entirely new concept around its functional design could have been created (not to say that has not happened, but stay with me). Encasing LED technology in a familiar shape, however, has made the transition from incandescent to LED much easier for consumers given that most fixtures used in homes and business across the globe were designed with that specific shape in mind. While rethinking the package an LED is presented in could have taken any number of turns, and could have been really fun to witness, it just did not make economical sense to do so. 

Regardless of the technology that makes it work, the A-shape bulb is here to stay. It is awesome to think how far we have come, really, when we remember that civilization relied upon fire as the sole source of light after dark for as long as humans have had the capability and curiosity to harness it. The invention of the light bulb, and more specifically the A-shaped light bulb, set humanity on a path toward even more innovation and advancement than is realized. We have watched as man-made lighting has quite literally changed the world, and the possibilities of what may come next are boundless. 

What’s next, I wonder?