An "RLM Standard" is not a military procurement protocol, a British measurement for screw threads, or a new digital file format for photographs – it is an acronym for a non-profit organization that developed and instituted industry standards for metal reflector shades. (1957, Rejuvenation archives)
If you’ve ever picked up one of those old metal factory shades – green on the outside and white on the inside – and wondered about a decal with the initials “RLM” on it, then this esoteric blog post will be for you…
With the release of our new family of Warehouse fixtures, I thought it might be timely to look back at a bit of history associated with porcelain enameled reflector shades – RLM Standards.
Prior to 1919, shade manufacturers (like the Central Electric Company of Chicago here in 1917) offered a wide array of reflector shapes and sizes, often based more on looking different from the next guy than on scientific principles of illumination. (1917, Rejuvenation archives)
Created and implemented by a group of lighting interests founded in 1919 as the Reflector Lamp Manufacturers Institute, RLM Standards were developed to further two goals:
1) Establish high minimum standards for the design and construction of industrial lighting units.
2) Simplify the selection of proper lighting equipment for specifiers, distributors and users.
Only a couple of years after its founding, the RLM Institute had this informative listing in the first edition of the Electrical Trade Publishing Company's 1400-page "EMF" Yearbook. By the way, the silvered glass X-Ray shade on the right was not an RLM-type reflector. (1921, Rejuvenation archives)
In 1936, the organization was reorganized and incorporated as the Reflector and Lighting Equipment Manufacturers Standards Institute. Below are a few select pages from our archive that provide some insight and context for this organization.
The Institute's Standard Specifications publication was a technical guide for the industrial lighting industry. A 1957 list of participants in the Institiute's RLM Inspection and Certifiaction Service reads like a Who's Who of mid-century industrial lighting manufacturers. (1957, Rejuvenation archives)
This spread from the 1957 edition shows the full specifications for the No. 1 RLM Dome - the original RLM shape that remains virtually unchanged today. (1957, Rejuvenation archives)
Fixtures with RLM-type reflectors are sometimes referred to as "barn" lights. This somewhat romantic moniker has more to do with marketing than manure, as these fixtures were vastly more common in industrial and commercial settings than rural ones. These photos from Bright Light Reflector Company's Catalog 40 show typical installations of their SILV-A-KING brand reflectors. (c1940, Rejuvenation archives)
In 1961, 40-odd years after their founding, the RLM organization got with the modern times by updating their typography as well as their standards, including a new circular label to replace their classic rectangular version with the clipped corners.
For all you Mad Men fans out there, here's what the guys who guided RLM Standards in 1961 looked like – you'd be hard pressed to find Don Draper in this crowd.
If this esoteric excursion into lighting nerdsville has left you hankering for even more fascinating historical background (and why on earth wouldn’t it?), check out these two links for further fun:
RLM ”QUESTIONS and ANSWERS” excerpted from the Institute’s official 1957 specifications publication.
Read through this feast of facts and you’ll know more about RLMs than your average lighting engineer…
A contemporary review of the development of steel reflectors, in General Electric’s Bulletin 20A from September 10, 1919, digitized by Google.
This 1919 publication from the year of the RLM Standards Institute’s founding compares new and old metal shades and introduces the first, and most well-known, of the RLM shapes – Standard No. 1.