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Author Topic: candle power to watts  (Read 7003 times)

Offline Loren

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candle power to watts
« on: November 01, 2003, 02:17:00 pm »
I typed this whole thing in and then it said I didn't exist. Hence the test post. Perhaps you are aware of this, but I'll post this anyway in hopes it may help you in dating your bulbs.

This is from the June 1910 edition of "Juice"
It's a letter sent out by a wholesaler to their jobbers.

On May first a sweeping change was made by the Incandescent Lamp Manufacturers in the method of rating their lamps. The old candle power basis of rating was entirely discontinued and a new wattage system was adopted for substantially all types of incandescent lamps. Lamps will no longer be known by their candle power value, but will be designated by watts and by watts on alone. In addition to this the lamps most commonly used will bear upon their labels three voltages in place of one as heretofore. This bulletin is issued in order to show why those changes have been made and how to order lamps under the new plan. The three voltage rating was previously adopted for the Gem and Mazda lamps in order to facilitate their use at more than one efficiency without employing the somewhat complicated method of rating used in the case of carbon lamps. As carbon lamps were rated in the past a single lamp often appeared on the schedules as three separate lamps, as for example the
16c.-p., 3.1 w. p.c. lamp was also shown as 12and a half c..-p., 3.6 w.p.c. and as a ten c.-p., 4.2 w.p.c. lamp. These three ratings applied to identically the same lamp but necessitated its use at three different voltages. It is apparant that it would have been very simple to place these three voltages upon a single label. Each of the more common lamps of the various types now bears a label upon which appear three voltages arranged in a vertical column, designated as top, middle, and bottom voltages. The middle voltage is two volts lower than the top voltage and the bottom voltage is four volts lower than the top voltage. The top voltage is emphasized as in pratically all cases the lamp should be used at top voltage in ortder to secure the best results and most satisfactory service. When burned at top voltage the lamp has the highest efficiency or consums the least current for the light produced, at the same time it delivers the best quality of light and gives satisfactory commercial life. At middle voltage more current is consumed per candle power produced and the life is somewhat lengthened. At bottom voltage the lamp consumes the most current for the light produced and gives a longer life.

So it appears that if you have a bulb other than a Gem or Mazda with the three voltages listed, it would be post May of 1910. I don't know when the Gem or Mazda began using the watt system as I don't collect bulbs. Just have an interest in electrical history.I now cross my fingers and hope this posts. I'm not gonna type it in a third time.