The Nernst Lamp – An Early Ceramic Glower

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In my research on light sources for a project here at KTH, I wandered across an interesting historical light source called the “Nernst Lamp.”  This source is very interesting; it was marketed by The Westinghouse Company for a while back in the early 1900’s and saw a total sale of over 130,000 units.  This lamp was invented by a pretty intelligent guy, Walther Nernst – a Nobel winner and the guy who discovered the Third Law of Thermodynamics (you know, the Law of Thermodynamics that says a crystal at absolute zero has an entropy of zero – theoretically of course).

A smart dude, that Walther Nernst.

This Nernst Lamp was a pretty interesting source – instead of using a tungsten burner, it used a ceramic rod that was open to the air and not enclosed in a vacuum environment full of Noble gas.  Since the ceramic rod didn’t oxidize, there was no need to enclose it.  Granted, it did get a bit dirty from time to time, but a cleaner kit was sold to maintain and upgrade the Nernst Lamp when it needed a little “loving.”  From the image above, the slits above the screw base and below the glower was a ballast of sorts.

A diagram of the “glower” in the Nernst Lamp:

Nernst-lamp-glower

What I found interesting about the Nernst Lamp is that it seemed to be marketed on the same principle that the whole CFL vs incandescent argument is based upon – better light with lower energy consumption, even though we know that both of those things are a crock in one form or another.  The company that filed the public holding on the Nernst lamp back in 1899, Nernst Electric Light, LTD, had many great ideas about how this source-interchangeable-glower lamp could be used in the market.  The company’s engineering consultant and board member, James Swinburne, was quoted as saying “Nernst’s Lamp is, in my opinion, the greatest invention in Electric Lighting, since the infancy of the industry.” He also happened to be the Vice President of the Institution of Electrical Engineers, too.  I mean, granted he was probably selling that thing Billy Mays style and all, but it was an interesting and popular source for a while.

I found a public holdings announcement from 1899 when the Nernst Electric Light company went public; in the holdings announcement, there was a list of things that make the Nernst Lamp “better” than the regular incandescent.  Does any of this stuff remind you of the CFL vs incandescent fight?

1. The consumption of power is, at most, 1.5 to 1.6 watts per candle power, being about 60 % less than the ordinary 4 watt incandescent lamp, thus saving three-fifths of the Electric Lighting bill.

2. The Nernst Lamp is pleasant and becoming. Its light does not fall off materially during the life of the rod, and, as there is no bulb, there is no loss of light through either internal blackening or external dust and dirt.

3. Unlike the present type of incandescent lamp, which can only be used commercially in circuits not exceeding 250 volts, the Nernst Electric Lamp can be commercially employed either with direct or alternating currents, up to any pressure compatible with safety.

4. The manufacture on a small scale of the rods or light-emitting bodies, has already resulted in rods which have lasted the equivalent of a year’s ordinary daily usage. Further experience in wholesale manufacture may be expected to give even better results.

5. The rod of the Nernst Electric Lamp with its wire mounts is detachable, and when worn out can be easily replaced by any one, the body of the lamp serving for an indefinite period, whereas the ordinary incandescent electric lamp is of no use when its filament is broken or the glass darkened. This is an economic advantage in favour of the Nernst Electric Lamp of the utmost importance.

6. The cost of production of the Rod will be exceedingly small.

7. The process of manufacture is very simple, and plant of an inexpensive kind only is necessary. There is no “flashing,” no electrical mounting, no expensive vacuum, and, comparatively, no waste, as a used-up rod merely means mounting another in the same wire; it does not mean scrapping a complete lamp. The holders of the automatic lamps are merely ordinary fitting work, demanding no new type of manufacture.

8. Compared with the Arc Lamp, the Nernst has many advantages in respect to–
(a) First Cost, which is about one-eighth to one-tenth of the Arc.
(b) Maintenance, the whole of the expense of carbons and trimming and the cleaning of the elaborate mechanism of the Arc regulator being saved.
(c) Pressure. Unlike the Arc, the Nernst Electric Lamp can be made to take very high pressures, for instance, a single rod for 400 volts is only about 2 1/2 in. long, and by arranging two in series in each lamp, there is no difficulty in running parallel on 1,000 volt circuits without transformers.
(d) Absolute steadiness and freedom from flickering and hissing.

I think Walther Nernst and James Swinburne had something with this removable-replaceable-filament idea.  I’ve been thinking about this for a while, mostly in the fact that we don’t recycle CFL ballasts – we just throw everything away when they die.  When I met Willem van der Sluis and he mentioned that he had the same idea of replacing a CFL’s fluorescent tube when it burns out and not the whole ballast and electronics, I was enthralled.  A few days ago I went on a trip to OSRAM here in Stockholm, and learned that when incandescents were first being manufactured here in Sweden, lamps with broken filaments were recycled – washed out, cleaned up, and re-filamented.  What a concept.  It makes me wonder whatever happened to the Nernst Lamp.  Why did we abandon the idea of making light sources that didn’t make so much waste?  The easy answer is that the Nernst Lamp became obsolete when carbon filaments were replaced by metal filaments.  Too bad we didn’t maintain the idea in some form.

Nernst Lamp images:

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nernst-lamp-4-keeper-instructions

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Thanks Spark Museum, Nernst, and Wikipedia!

5 COMMENTS

  1. Very nice article – The parallel with the CFL vs. incandescent is very interesting I think, and quite valid not only in terms of energy efficiency, but also in terms of lamp structure. Like CFLs the Nernst lamp has a more complex, and thus a more costly construction than incandescent lamps.

    Interestingly, Nernst glowers also do need a sort of driver to properly operate because 1/ the ceramic is non-conducting at room temperature and thus need to be heated for “ignition” and 2/ at its optimum operating point the hot ceramic has a negative voltage-current characteristic which requires a current-limiting system to avoid current runaway. In fact these two problems, although of different origins, are also found in CFLs and are the reason for the use of an expensive driver system. In Nernst lamps the driver is nowhere near as “complex” as in CFLs (transistors did not appear before 1947!) but there was still the need for a series resistor (i.e. current limitation) and for a switching system (heating of the glower) which makes the system complex and much more expensive than the simple incandescent lamp. What’s more, the cost of the glower itself was higher than that of tungsten filaments on account of the need for rare-earths oxides of high purity.

    So, when the so-called “half-watt” (referring to the energy consumed per candle power) tungsten filament lamps appeared in the early 1910s, the less efficient and more expensive Nernst lamp could just not compete. I think there is always something interesting to learn from that; the high cost of the Nernst lamp was the primary reason for its relatively modest success, even in the days of the carbon filament lamps – something, I think, we should bear in mind when thinking about 10$+ CFLs or 30$+ LED lamps that have to compete with 1-2$ incandescent and halogen lamps.

  2. do you know of anyone that still makes nernst glowers or lamps? I’m looking for a very hot pinpoint blackbody for the Mid IR, 2.5 to 25u. SiC is nice but would like something hotter.

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