Oven Lamp usually has two glass color, one is clear glass, the other one is smoked deep color glass.
Why glass oven light bulb is with smoked deep color? it is because that the tungsten filament is covered with a thick layer of red phosphorus, if the oven bulb is lighten on, tungsten filament will create a lot of heating, red phosphorus will be evaporating and adhere to the glass, then the glass looks smoked.
1>. All the lamp is with clear glass, filament is with red phosphorus, before life testing at factory, glass is clear.
2>. After life testing at factory, the glass will change to smoked deep color.
3>. However, because for different lamp, the filament has different amount of red phosphorus, so the glass color is a little different, some bulb maybe a little deep, some maybe a little lighter. This color difference is always there, because so far no one can control the red phosphorus same amount for each lamp.
Oven Lamp usually need to be 300 degree high temperature, because it is used inside Oven, which is with high temperature.
However, 300 degree high degree centigrade oven lamp is with higher cost than ordinary oven lamp, and it looks almost same as ordinary temperature ovan lamp. So it is better to know the difference between 300 degree centigrade oven bulb and ordinary temperature oven bulb, the difference is as below:
1. The glass part and tungsten filament part is same, no difference.
2. Lamp base is different. There must be soldering point on top of the lamp base, because only tin soldering point can withstand 300 degree centigrade high temperature. However, because tin usually contains lead, it’s not good for environmental testing, we have to use Lead-free soldering wire.
3. The glue between lamp base and glass part must be full and enough for 300 degree high temperature oven lamp. Ordinary temperaturer oven bulb only has some glue on the bottom part of the lamp base, the glue is between lamp base and glass part. However, for 300 centigrade degree high temperature oven lamp, the glue must be applied all over the contact surface between lamp base and glass part, because high temperature does harm to glue, that is why the glue must be all over the surface and must be enough.
When you need to buy a 300 centigrade high temperature oven bulb, you must be aware of these differences. If you use an ordinary temperature oven bulb for a oven, the oven bulb usually has a much short life.