Updated 26-VII-2019

Marvin Pipkin

This article is based on a document of fellow lamp engineer and collector Edward J. Covington, which appeared on his website of biographical sketches of persons involved in the lamp industry. Following his passing in February 2017 and with kind permission of his family, Ed's words have been preserved and subsequently expanded with new material by this author, to maintain continued access to the research he initiated.

Marvin Pipkin holding samples of his diffuse bulb developments : Q-coat (left) and inside frosted (right)

Marvin Pipkin (18 Nov 1889 - 7 Jan 1977) is best known as the inventor of the inside-frost process of bulbs for incandescent lamps, which was developed in 1925, as well as the improved "Q-coat" process, developed in 1947, which consisted of an application of silica to the inside of a bulb.

Marvin Pipkin was born in the Christina area south of Lakeland, Florida and was one who had a pronounced Dixie accent. He was the son of David M. and Catherine (Moore) Pipkin. His father was a farmer and grove owner and planted the first citrus trees in the Medulla and Christina areas.

Pipkin received his primary education in Lakeland and his secondary education at the Summerlin Institute in Barlow. One of his Summerlin classmates remembered Marvin as a shy, gawky, sandy-haired, freckle-faced boy who knew more chemistry than all the rest of the class put together.

After graduation from high school Pipkin joined a prospecting firm for a year and then worked, for a short time, at the International Agricultural Corp., later known as the International Mineral and Chemical Corp. of Barlow.

Pipkin attended Alabama Polytechnic Institute (API) and received a Bachelor of Science degree in Chemical Engineering from that institution in 1913. After working in fertilizer and phosphate laboratories in Barlow for a year he returned to API and, in 1915, earned a master's degree.

On 5 Nov 1917 Pipkin enlisted in the Army in Jacksonville. Because the Germans had introduced poisonous gas into warfare there was a need for persons with a chemical background to work on gas masks. Pipkin entered the Gas Defense Department as a private and was posted to the General Electric laboratories at Nela Park in Cleveland.

One of the first discoveries that emerged from the Nela laboratory was due to Pipkin. He found that the activity of charcoal for phosgene (a highly poisonous liquid) could be significantly increased by the introduction of hydrated manganese dioxide into it. Subsequent findings and understanding led to accurate determinations of the effect of water on the absorption of gases by charcoal. Pipkin attained the rank of Master engineer, senior grade. After his service he remained at Nela to work in the Lamp Development Laboratory.

The glare from incandescent lamps was something many people wanted to reduce. A common technique used on early incandescent lamps consisted of an outside acid etch on the bulb. However, such a process led to remarkably reduced strength of the bulb. The rough external surface was also inclined to attract dust and dirt, and caused marked reduction in light output during the life of the lamp.

In 1925 Pipkin developed the inside frosted lamp in such a way that did not weaken the glass (U.S. Patent 1,687,510). It was a process that was standard for about 70 years, but in more recent times is frowned upon due to the large quantities of hydrofluoric acid that are required. The disposal of the used acid is environmentally unacceptable today, and the costs associated with neutralisation of the waste materials has made the process generally prohibitive in most countries of the world. However in 1947, Pipkin also developed a still improved bulb diffusion process, known as the Q-coat, was achieved by means of an inside coating of fine silica particles on the bulb (U.S. Patent 2,545,896). This quickly became the preferred technique in America and the so-called 'Soft White' bulbs quickly displaced the earlier inside frosted types. However in the rest of the world the so-called 'Pearl' inside frost process held court, and the silica-coated bulbs were reserved for premium-cost and decorative lamps. The picture above shows Pipkin holding up a sample of each of his developments.

The Q-coat process was superseded by the more economical "E-coat" or electrostatic process in the 1970s.

Pipkin also held several patents on photoflash lamps.

He retired from Nela Park in 1954 and resettled in his home town of Lakeland. He had married Kathryn Patricia Enright (d.1957) on 21 Jul 1919 and they had three children. Pipkin passed away at the Lakeland General Hospital in 1977 after a lengthy bout with cancer.

  1. US 1,520,437 - 23 Dec 1924 - Process for Catalyzing Gaseous Reactions
  2. US 1,687,510 - 16 Oct 1928 - Electric-Lamp Bulb
  3. US 1,706,182 - 19 Mar 1929 - Colored or Diffusing Coating for Incandescent Lamps and Similar Articles
  4. US 1,718,487 - 25 Jun 1929 - Apparatus for Frosting Glass Articles
  5. US 1,900,463 - 07 Mar 1933 - Bulb and Method of Coloring Same
  6. US 2,053,164 - 01 Sep 1936 - Incandescent Lamp and Method of Manufacture
  7. US 2,114,201 - 12 Apr 1938 - Flash Lamp
  8. US 2,142,372 - 03 Jan 1939 - Flash Lamp (with Robert E. Worstell)
  9. US 2,199,857 - 07 May 1940 - Flash Lamp
  10. US 2,215,477 - 24 Sep 1940 - Method of Manufacturing Wire
  11. US 2,285,125 - 02 Jun 1942 - Flash Lamp
  12. US 2,291,983 - 04 Aug 1942 - Flash Lamp
  13. US 2,297,981 - 06 Oct 1942 - Method of Frosting Glass Articles
  14. US 2,306,563 - 29 Dec 1942 - Flash Lamp
  15. US 2,361,495 - 31 Oct 1944 - Flash Lamp
  16. US 2,383,076 - 21 Aug 1945 - Flash Lamp and Method of Manufacture Thereof
  17. US 2,473,888 - 21 Jun 1949 - Lead-In Wire for Electric Lamps and Similar Devices
  18. US 2,497,517 - 14 Feb 1950 - Flash Lamp
  19. US 2,545,896 - 20 Mar 1951 - Electric Lamp, Light Diffusing Coating Therefor and Method of Manufacture
  20. US 2,571,607 - 16 Oct 1951 - Coated Flash Lamp and Manufacture Thereof (with J. Dean Johnson)
  21. US 2,615,472 - 28 Oct 1952 - Glass Tubulature for Feeding Mercury
  22. US 2,626,874 - 27 Jan 1953 - Method for Forming Silica and for Coating Lamp Bulbs
  23. US 2,726,527 - 13 Dec 1955 - Flash Lamp
  24. US 2,781,654 - 19 Feb 1957 - Coated Lamp

  1. "The National in the World War (April 6 1917 - November 11 1918)", General Electric Co., 1920.
  2. "He Made Inside-Frosted Lamps Possible", GE Light Magazine, Vol.4 No.4, Apr 1926, p.12.
  3. "The Inside Frosting of Incandescent Lamps", Marvin Pipkin, Industrial and Engineering Chemistry, Vol.18 No.8, Aug 1926, pp.774-776.
  4. "Lauds Invention of Inside-Frosting", GE Light Magazine, Mar 1927, p.7.
  5. "U.S. Circuit Court of Appeals Upholds G-E Inside Frost Patent", GE Light Magazine, Mar 1938, p.21.
  6. "A Revolutionary Development in Incandescent Lamps", Marvin Pipkin, General Electric Review, Mar 1949, pp.14-17.