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Author Topic: Many questions about lightbulbs  (Read 18573 times)

Offline Yoshi

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Many questions about lightbulbs
« on: August 24, 2003, 02:39:00 am »

Many questions about lightbulbs

Hi, I've been writing down questions about lightbulbs as I find them. I didn't want to make a post out of one question only, so I have several here:

1.-Numbers on bulb stems.- Ok, the forever unanswered question is, what are those handwritten numbers and letters written on bulb's stems??? Does anyone know? What was their purpose? I have absolutely no idea.

2.-Bulbs made after 1900: Handblown or not?.- My theory is that most bulbs made after 1900 were handblown, but into molds, so that they would acquire a certain exact shape, everytime. Does anyone think the same? I have a video from the History Channel in which a guy in a lightbulb factory blows a lightbulb onto a mold on the floor, which he opens and closes with a pedal. Once the bulb is blown, it is twisted before being pulled out, a process which I suspect is the reason for a certain glass effect that looks like a twist, that I have observed on many bulbs from the 1900's-1920's. Oh and just to mention it, I simply can't understand why some people think that antique bulbs were blown from the top rather from the bottom, just because they have a tip...; what upsets me the most is that they say it with all the confidence in the world.

3.-How do I wire old sockets?.- I haven't figured it out. I have been unable to open old Edison sockets so I can re-wire them. Is there any special procedure involved? I would like to wire my two edison sockets but I don't want to risk damaging them in the process. This has not been a problem with my Thomson-Houston and Westinghouse base sockets.

4.-Do you have an antique lightbulb on display in your workplace?.- If so, what kind of bulb is it, and how is it being displayed? I have a very neat (but non-working) tipped, clear national mazda lightbulb with rare carbon paste bottom spokes displayed on my computer desk, which is screwed into a square porcelain socket. I chose this non-working bulb so that I would not lose any money if it suffered an accident. Still an awesome bulb to look at. I don't know why but I have a special fondness for the most common of antique lightbulbs (the 1910's 40-60w mazda lightbulb). Maybe because it was a lightbulb that illuminated the lives of millions of people that are no longer with us? I have about 10 working ones (and would still buy more if offered cheap enough!).

5.-How do you prefer your lightbulb's bases?.- do you like them with the original patina, or do you like them real shiny just like they were the day they were made? I used to like them shiny but I quickly realized that aged metal was more fun to look at. More history behind it.

6.-What thoughts come into your mind when you look at your old lightbulbs?.- I think of things like a family dressed up in 1910's clothes eating dinner together, being illuminated by the lightbulb in question. Or I have also thought about the fear of an imminent air raid when looking at the WWII blackout bulbs. I have also thought about the people who assembled such bulbs and what their lives might have been like, when looking at elaborate bulbs like my bryan marsh mazda 60w bulb with heavy copper supports. Those supports were probably cut, bent and then added one by one, all by hand! Remember that our antique lightbulbs (yours and mine) are the work of people that are no longer alive, the legacy left behind by the people from the past... and also think about the many owners that they may have had and the great care from every one of them.

I would really like to hear your opinions.


[This message has been edited by Yoshi (edited August 24, 2003).]
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Offline Chris W. Millinship

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Many questions about lightbulbs
« Reply #1 on: August 24, 2003, 08:39:00 am »
Lots of interesting questions there!

1.-Numbers on bulb stems.
I think these sometimes refer to the factory and production line where the bulb was made. Often, especially on earlier carbon lamps, they are also the filament voltage or resistance since carbon filaments varied so much. Ed Covington will know exactly what most of them mean though. Different manufacturers did different things. I`ve even got one somewhere with a little smiley face drawn on it - something which apparently is more common than I originally thought cos there`s one at the Edisonian museum site with the same thing!

2.-Bulbs made after 1900: Handblown or not?
I think it depended on where they were made. Small bulb-makers might have had them hand made while larger companies producing in big volumes would have had machines. Read the Story of the Lamp here on this site for some history of lampmaking, with an emphasis on Osram/Robertson lamps. Generally if a lamp`s glass comes straight out of the base and curves round to the tip in one sweeping form, it`s handblown in free air, with the aid of simple formers. If the glass leaves the base with a sharp outward "bulge" and continues up to the tip in a fairly straight line, it`s moldblown. But whether a machine or a glassworker blew it is uncertain.

3.-How do I wire old sockets?
I guess you havn`t figured out how to get the brass shell open yet? Don`t worry, took me a while too. You`ve probably got types that snap together. To open them, press quite firmly as shown:

...and lift the back/top half of the shell upwards. Sometimes it can be rather tricky especially if it hasn`t been opened for the best part of a century! Some sockets are engraved "press here" where you should apply pressure, some aren`t. You can also try the other side of the turnkey/pull cord hole if it won`t come off.
Inside the connections are straightforward - one screw each side of the porcelain inner. Hot lead should go to the center contact (if you`re using a cord with a polarized plug). There isn`t usually a place to hook a ground wire cos early wiring didn`t have ground wires, so take care and apply a bit of extra insulation tape/sleeving if you`re concerned about any connections.

4.-Do you have an antique lightbulb on display in your workplace?
Not at work, though most newcomers these days go to the office first so occasionally my co-workers will see some of them. Now and then one of them will take a bit of an interest too! Here at home on the other hand, well I can count over a hundred bulbs out on show including that antique pendant fixture in the photo above which hangs right over my head, though I don`t light it very often and never at full power.

5.-How do you prefer your lightbulb's bases?
Ideally I like`em as clean and tarnish free as possible. It`s nice to see a 1900s lamp with a base as clean as a modern one, like this one, just as the day it was made:

Otherwise, I`ll clean the surface dirt off both glass and base but won`t specially polish tarnished lamp bases back to bright yellow brass. I tried it a couple times and it just didn`t look right. A bit of a patina is quite nice to have so long as it`s not just outright corrosion. I`m not keen on badly corroded brass bases that are almost black, but unfortunately a great deal of the earlier British lamps I find are in this condition. If I ever find a gentle but effective treatment I can use to clean those bases a bit, I`ll definately do it. My biggest concern over cleaning lamp bases is causing damage to the lamp - either by breaking the filament due to the vibrations caused, or by seperating the base itsself from the glass. Neither of which are desirable at all!

6.-What thoughts come into your mind when you look at your old lightbulbs?
I`ve often tried to imagine what life must have been like a century ago with whole houses lit by these 8cp carbon filament lamps, but somehow my imagination is a bit limited so I`d really need to experience it myself. In the future I`d love to have a "1900s room" where I`ll feature some of my early lamps, fixtures and fittings, but also it`d be fitted out exactly as an early "electrified" room would have been. Surface routed wiring, turnkey switches, carbon bulbs, proviging the sole illumination. Maybe I`ll do it, maybe not. It would be a nice project though.

I remember when I got the first of my WW2 blackout transformer-lamps, one evening I tried using it as the only light source in this room. A lighting level that hadn`t been seen for 60 years - just enough to get round without banging into things. Must have been very strange indeed to have most of your house lit at this sort of level for such a long time witn no option of having it any much brighter. Of course I don`t doubt that one or two rooms (with proper blackout boards fitted to the windows) would be lit as normal. But still, makes ya think.

At least you`d be able to look outside on a clear night and see the stars! Not like today....


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Offline James

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Many questions about lightbulbs
« Reply #2 on: August 24, 2003, 09:28:00 am »
Hi Yoshi,

Regarding your comments on glass bulb production, I believe you are about right.  Certainly by 1890 the vast majority of bulbs would have been blown by the method you describe and few, if any, would have still been blown freely into the air without moulds.  It was not until 1912 that Corning had almost perfected its "Empire" machine for the mechanised forming of glass bulbs, the first of its kind, which was capable of blowing 7 bulbs per minute.  It was a tremendous advance over the 2 bulbs per minute that a glassblower and his gaffer could make together, although it still required a glassblower to gather glass from the furnace onto an iron blowing tube, and then transfer this to the machine for final shaping into the mould.

Around 1915 GE unveiled its considerably more advanced Westlake machine which was a rotary device capable of blowing about 25 bulbs per minute.  This machine could feed itself with glass automatically and complete the entire bulb-blowing process without human intervention.  Bulbs were still blown on the end of a metal tube though, and had to be cracked off at the end of the cycle.  This type of machine was also widely used in the UK, where modified versions, the Ohio and Ivanhoe became very popular.  These were essentially Westlakes but which blew 2 or 4 bulbs instead of one at each machine position, doubling or quadrupling the production capacity.  The Westlake is an unusual machine to see in operation, looking almost human because it replicates perfectly the motions of a glassblower.  It sucks a gob of molten glass onto the end of an iron tube, then swings the tube from side to side to roughly inflate the shape, before dropping it down into a mould and blowing it whilst rotating the bulb in the mould.  12 such tubes are mounted vertically on a circular machine and the whole machine rotates continuously with glass being taken in at one end and finished bulbs being cracked off after the machine has made a full revolution.

Meanwhile in Europe the preference was for Philips' so-called Carousel machines, which blew glass at a slower speed than the Westlakes but they did not require a blowing iron tube and production was much more efficient.  Some of these original machines still operate at Philips' glass plants in Poland, Egypt and India.

It was not until 1926 though that the present method of bulb production was perfected, through Corning's development of the Ribbon Machine.  In fact so significant was its development that at the time it was known simply as "The Corning Machine", as if there was no other machine in the world.  Every principal lampmaker worldwide now uses this technology.  Although Corning invented the machine others were later given a license to copy it, GE, Philips and the joint glass company of the British lampmakers each buying one machine from Corning and making four copies of their own. Corning then exited the business, selling is glass bulb operations out to Sylvania around 1992.  Today only two companies worldwide are active in building Ribbon machines, these being Philips Lighting in Belgium and UK Glass Technology firm Cannon Engineering.  Blowing bulbs at the phenomenal speed of up to 2000 per minute from a single production line, much faster than the eye can follow, it really is an incredible sight to see if you ever get the chance!  The Ribbon Machine has often been referred to as the fastest and most efficient automatic production mechanism of any kind on Earth, something which is easy to believe when you see one in operation.  With almost two million bulbs being blown every day from the faster lines, just a handful of machines located in the USA, England, Belgium, Hungary, Russia, Japan, India and Iraq are satisfactory to meet almost the entire worldwire demand for glass lamp bulbs.

Anyway, if you should have any further interest in precise details of glass bulb development I have a couple of PDF documents on the history, about 1MB each which I am happy to email to you.

Best regards,


[This message has been edited by James (edited August 24, 2003).]

Offline Yoshi

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Many questions about lightbulbs
« Reply #3 on: August 26, 2003, 04:44:00 am »
Hey, thank you for your great replies!! As always, very very interesting facts!

I tried to open my sockets, yes they are engraved with "press", but they are impossible to open! I'm not too worried about them at the moment, I just wanted to know if they could be rewired or if they were doomed to stay unwired forever. I did try hard to open them but they just won't open. They are sockets patented in 1910. Thanks for the tips, Chris!

Yeah, it's hard to find people that might become interested in bulbs, but I think I found one the other day! He's a professor in computers and I gave him a non-working edison mazda lightbulb in neat condition, and he liked it a lot! He looks forward to buying a few working bulbs.

I agree about base corrosion, but I like the base to be in the same condition all around (for example, all lightly covered with patina or all shiny and clean, but not clean on one side but oxidized on the other).

Hi James, you know so much! For me, there is still so much to learn about lightbulbs. Thank you for your highly detailed story! yes, I would like to receive your pdf document about glass bulb development, please email to (and no, my name is not tucson! It's just a username invented by my dad, I don't know why he chose it).


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Offline Mónico González

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Many questions about lightbulbs
« Reply #4 on: August 27, 2003, 04:14:00 am »
Hi everybody!

About brass sockets, I must say that here, in Spain, the most popular one was during many years (and now still being quite easily found), a four-piece type that are made as follows:

- A brass threaded sleeve (the Edison screw itself) that are affixed by means of screws to an insulating ceramic piece. At this insulator are also the central contact terminal and both lead-in screws where the wires can be attached.

- A cup-shaped brass rear cover, fitted with a female retaining 10mm diam. screw (5/8" Gas type in E40 models) sometimes these nut are fitted with a little pressure screw to avoid unscrewing from raccord.

- Another brass moulded protective outer sleeve, screwed over the above mentioned cup.

- An insulating inside female-threaded ceramic ring, that threads over the Edison screw piece. This ring closes the whole socket and protects the thread to make contact with any other metal parts.
This is the first part that can be removed when dissasembling the socket.

When wiring these kind of sockets, one must be careful to avoid any wire make contact with rear cup. If this happens, an electric shock can result if the socket are touched with bare hands, especially at our 220-230 volt mains. Also if both wires makes contact simultaneously, a short circuit can occur; so these type of sockets are not very well seen by CE electric rules, so they tends to disappear from European market.
Another thing to be in mind when wiring, are that neutral wire must be connected to thread side and live to center contact of socket. (like in every Edison's)

I like very much and prefer these old-style sockets by its classic "look", and when I purchase any kind of fixture fitted with new CE homologated sockets (very fragile and ugly) I always substitute these by traditional brass ones.

Also exist a smaller type, the E14 or SES version of these brass sockets, so as a Mogul or Goliath E4O one. This latter are quite hard to find actually, but I acquired one of them three months ago.

The regular E27 version additionally has the possibility of can be fitted with a specially designed shade-holder consisting in a machined piece made from brass, constituted by a skirted ring with three emerging down-bent flanges or arms fitted each one with a retaining screw to suspend the shade. A so configuration permits the heated air surrounding the bulb to flow upwards, allowing the natural cooling of the lamp.
The shade-holder's ring part are placed around the outer jacket's front end and locked in place by the ceramic ring.

I'm planning to add some more pictures and a lot of info on these brass sockets to my website very soon, not only on E27 but E14 and E40 too.

BTW. here are a pic of one of these sockets currently hosted in my website:

Best regards,
M. Gonz?lez.
« Last Edit: April 09, 2008, 12:03:10 pm by M?nico Gonz?lez »

Offline Alan Franzman

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Many questions about lightbulbs
« Reply #5 on: August 31, 2003, 12:48:00 am »
Originally posted by Yoshi:
I tried to open my sockets, yes they are engraved with "press", but they are impossible to open!

I have an idea that may help you loosen them - if someone (maybe yourself) tried to take the socket apart by pulling on the end cap without pressing on the "press" mark, this could have caused the locking tabs to become wedged tightly together.  You may be able to free them by first pressing against the cap (pushing it onto the socket) which should release this locked condition, then press where it says "press" and try pulling the cap off again.  It may take a lot of pressure; you should actually be able to make the outer shell flex inward noticeably.  Then while holding this pressure, pull on the cap adjacent to where you're pressing the shell.  You should be able to move it at least a little, then from here rock it back and forth until it comes free.  A little oil between the cap and outer shell may help too.

Alan "A.J." Franzman

Email: a.j.franzman at verizon dot net


[This message has been edited by Alan Franzman (edited August 31, 2003).]

Offline Yoshi

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Many questions about lightbulbs
« Reply #6 on: September 06, 2003, 03:53:00 am »
Hello Alan,

Thank you for your tips! Unfortunately, it didn't work... These sockets are rock solid. The br*** is real thick, so I could not get the br*** to bend noticeably (I did not use tools because I didn't want to damage them). I'm probably not trying hard enough because of the fear of damaging them. I used my bare hands and now my fingers hurt... Anyway, opening them is not absolutely necessary, I just wanted to know if it was possible. Still, if someday I decide I want to try again, now I know how to do it! Thanks guys.   By the way, br*** is "b r a s s". The board is censoring part of the word.

[This message has been edited by Yoshi (edited September 06, 2003).]
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Offline Tim

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Many questions about lightbulbs
« Reply #7 on: September 06, 2003, 05:26:00 am »
Originally posted by Yoshi:
By the way, br*** is "b r a s s". The board is censoring part of the word.

Sorry about that, hopefully I fixed it.  I was messing around with some censoring options after the assult of "interesting" posts here the other night (now deleted.)  You may or may not have saw it...

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Offline Yoshi

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« Reply #8 on: September 06, 2003, 05:41:00 pm »
Hi Tim,

Yes, I did see those posts. It looked like some little kid found this board and tried to show us his immaturity. Glad you deleted them.

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Offline debook

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Re: Many questions about lightbulbs
« Reply #9 on: March 07, 2008, 05:43:56 am »
Lightbulbs were still being widely blown by hand in free air as late as the 1920's, it was not a problem for a skilled glass blower to make to the exact size and shape required. Many specialised bulbs are still made this way. the use of a dip mould mentioned above allowed lower skilled blowers to be used. Of course there were many different approaches used.
Frank Andrews