Fact & Fiction
Much can be said on the boundaries broken by Lewis Latimer. His entry into an elite group of electrical pioneers at the dawn of the electrification of the world is beyond any doubt a story of immense achievement for any person of the time. To have achieved such success as an African American is further impressive. Simply put Latimer's skill set far outweighed social stereotypes and stigma's of the era, his skill and knowledge earned him high and impressive positions.
That said, much like other figures in the history of technology, especially those who had a connection to Thomas Edison in some form, not all current teachings are true. In this section we will highlight the achievements but also dispose the myths of Latimer's work. Despite the teachings that the following will prove incorrect, the following statements are all backed by period documentation, much of which is presented below.
Theory: Lewis Latimer Invented The Carbon Filament
There is a current trend to credit Latimer with "inventing the carbon filament" thus allowing Edison to succeed. This is simply not true, and not even possible. Edison and Latimer were both working with carbon filaments years prior to Latimer ever steeping foot into an Edison company's office. Lets study some evidence behind this misunderstanding.
To properly evaluate the accuracy of the above theory one must first observe common language used in patent "legalese" of the era. Patents were then, and still are today based on the inventor's patent submission being different from previous issued patents. The term "improvements" is used extensibly and loosely in patent working of the era. Simply put the term "improvements" is a subjective description of the inventors different and unique approach to a product, but is in no way a confirmation of actual "betterment". Of the thousands of patents applied for and issued by the US Patent Office in the early developmental days of incandescent lighting, the majority of these patents are for "improvements", yet many are ideas that were never used in production, legal protection for work product, or in many cases simply ideas that eventual failed.
The two patents in question are issued to Latimer under the assignor-ship of the United States Electric Lighting Company. Latimer began his career in the electric lighting field as general assistant and draftsman for Hiram Maxim. Latimer had an immense influence on the success of USEL, personally directing the installation of the earliest installations for the company. When USEL expanded to the UK, it was Latimer that was sent to England to train glassblowers to manufacture the Maxim lamp. It was in England that Latimer and his wife would experience racism to a level that they never experienced in the US.
Returning to the patents. patent 247,097 covers improvements in the method of attaching filaments to lead in wires. Lead in wires are the conductors that extend from inside of the glass "envelope" of a light bulb to the outside world to provide a means of electrical contact to the filament. Maxim used tiny threaded nuts and bolts made of platinum to attach the (carbonized paper) paper to the (platinum) lead in wires. Latimer's patent covers using flattening and folding the ends of the platinum lead in wires and passing them through slots in the filament. This patented idea was never used. Not a single surviving Maxim lamp makes use of this patents technique, and even post Maxim and Latimer involvement with USEL, the platinum nut and bolt filament attachment method was used.
The second patent, US 252.386 covers improvements in manufacturing of carbon filaments. Maxim paper filaments to be exact. While Latimer was of great importance to the filament produced by Maxim, Maxim filaments were not of high efficiency nor were they long lasting.
Conclusion: Lewis Latimer did invent two filament related techniques, but did not invent the carbon filament. The carbon filament goes back to inventors testing prior to Edison and Maxim's work. While a lot of dates and theories exist, Joseph Swan experimented with carbonized paper and other materials as early as 1860.
Fact: Edison Improved His Own "First" Filament in 1880
Edison's first glimpse of success with a practical incandescent lap was recorded on October 21, 1879. This lamp made use of a filament of carbonized cotton thread. This material was reported to have burned for 40 hours. The voltage and light output for this test is subject to debate, however this date set the stage for Edison's success. The use of a high resistance, carbon filament in a high vacuum was Edison's ultimate answer to the incandescent lamp. By November of 1879 Edison had found that stamping and carbonizing horseshoe shaped forms from "bristol board" paper, and at the end of December 1879 Edison opened his Menlo Park laboratory to the public for a demonstration. While these lamps were his most successful to date, the paper filament was extremely fragile and the manufacturing process was daunting. Furthermore the short fibers and inconstant manufacturing qualities of the bristol board created weak spots that formed higher resistance areas of the filament which would cause premature failures.
Edison knew he needed a material with stronger fibers, and looked to natural vegetation to find the ultimate material. Ultimately in mid 1880 Edison found that bamboo, specifically a Japanese species known as Madake, had the proper form of long parallel grain grain needed to produce a consistent resistance across the length of material.
By mid 1880 Edison was achieving burn times in excess of 1,200 hours at 16 candlepower with bamboo filaments. As vacuum technique improved, burn times exceeded. By 1881 Edison achieved an average run time of 3,000 hours. The lamps eventually burned so long that the darkening formed on the glass as a result of the expelling of carbon from the filament (a phenomena that would eventual lead to the discovery of The Edison Effect and the development of the vacuum tube) that the bulbs became highly inefficient yet the filaments were still in fact and burning.
By mid 1881 at the Paris Electrical Exhibition both Edison and Maxim's systems were on display. Otto Moses observed in a letter from August 26, 1882 that the Maxim lamps have off a harsh light and that the system was constantly inoperable. Multiple lamps were burned out. The Maxim lamps ranged from 4-12 candlepower. Edison's standard lamps were 8 and 16 CP at the time. Maxim was not able to achieve higher output from his product, at least none that were documented or survive.
Edison made use of the bamboo filament as the standard until the formation of General Electric Co. in 1892, and some larger candlepower continued to make use of bamboo into the turn of the century. While Edison continued to improve ways of manufacturing, treating, and attaching the bamboo filament, the improvements needed for Edison's decade plus success with the material was set well before Latimer joined the Edison company.
Conclusion: Lewis Latimer did not improve upon Edison's filament. All pertinent work in Edison's filament that was used for over a decade took place before Latimer's arrival at the Edison Co. The filament work that Latimer did conduct was for the Maxim Lamp, a product that used an inferior performing filament made from the same material that Edison first used in late 1879 and abandoned by 1880 due to its lack of strength. Latimer's work with the Edison company had nothing to do with filament development and had he not joined the Edison company the Edison lamp would have differed in no way.
More to come....
Fact: Lewis Latimer did in fact have two patents pertaining to improvements in carbon filaments.