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GE Q-Coat Soft White!

GE Q-Coat Soft White!

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Found a box of these with three still present at Value Village. Box has an old Safeway price sticker. Can someone give me a rough date? I'm thinking early '70s.

When I was small, at my mother's house there was a 25w version of a bulb like this, with its Q-coat soft white and blue glass base insulator. One of my presents at an early age was a reel-cord trouble light; the bulb died in there after the fixture hit the floor. I need to buy another one of those lights for posterity one of these days before everything becomes integrated LED, they are one of my favorite types of incandescent fixture, right up there with the banker's lamp and vaportight fixtures.

What was the benefit of the Q-coat? As I remember Dave Silverliner explaining it long ago it was an inside frost bulb with the same silica finish as soft white. Was this an attempt to reduce glare, etc?

IMG_5337.JPG IMG_5338.JPG IMG_5339.JPG IMG_5340.JPG

Light Information

Light Information

Manufacturer:General Electric
Model Reference:100A/W
Lamp
Lamp Type:Incandescent
Base:E26
Service Life:750 hours
Fixture
Location:Fairbanks, AK
Electrical
Wattage:100
Voltage:120
Physical/Production
Factory Location:USA

File information

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Album name:ace100w120v / Incandescents
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Date added:Nov 15, 2018
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James
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Nov 16, 2018 at 12:57 AM Author: James
The Q-Coat was a lamp made with a chemically-deposited layer of fine titanium dioxide particles on the inside surface of the bulb, to give a softer light than inside frosted but with a higher light transmission than the real white opal glass bulbs that used to be made previously for low-glare applications. The way of making the coating was interesting - the bulb was placed over a small ‘candle’ type device having a wick dipped in a liquid of titanium tetrachloride insteas of the usual oil or wax. After setting fire to the wick the TiCl4 burned with a smoky flame containing titanium dioxide fumes - a powerful white colour dye. These condensed all over the cool inner surface of the glass.

This process was introduced in the 1940s, and replaced in the 1970s/80s by the E-Coat (electrostatic coating). That is a cleaner and easier process in which the glass bulb is heated with gas flames from outside, and an electric charge is applied to the metal gas burners and is carried through the electrically-conductive flames to charge the glass negatively to something like -20kV. The white powder is blown into the tube via a piece of silicone tubing which gives it a small positive charge of about +10V. When the positively charged powder enters the negatively charged bulb it is attracted to the glass and forms a particularly even coating.

The old Q-coat bulbs had a slight drawback that the coating was thicker directly above the flame on the bulb crown than the sides. With E-coat it was possible to attain more uniform coatings, which reduced light losses in the thicker areas, and allowed a higher lumen lamp. It is not always easy to see the difference visually between E and Q coat lamps but if your package has the lumen values stated, it might be possible to compare those with old GE catalogues to see when the values increased and identify which you have. It could be that you have here one of the first ever E-coat lamps, which would also be a very important lamp to save! The coatings on those were not so thin or good as today, hence the visual difficulty to identify it. Only way to really know is crack it open and analyse the chemistry and shape of the particles in the electron microscope! I have one or two from around this period that I could not properly identify yet.
ace100w120v
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Nov 16, 2018 at 12:25 PM Author: ace100w120v
It's thick, but not so thick as to be completely opaque. Is E-coat the typical soft white we see now?
Lumex120
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Nov 16, 2018 at 12:52 PM Author: Lumex120
So it's t h i c c?

Any machine is a smoke machine if you operate it wrong enough.

ace100w120v
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Feb 23, 2019 at 07:58 PM Author: ace100w120v
Fairly thick. I can try to light one.
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