So, Just curious for some reason..

What would happen if you left say a droplet of water (Distilled) in an Incandescent lamp and put it under vacuum, assuming that the water droplet has no pockets of oxygen in it what would happen? Would it have any effect on the filament? would it corrode anything? or would it do nothing at all?

The lamp would explode under the pressure of the steam.

Not from 1 droplet !

Most likely it would make some sort of cycle, transferring heat away from the filament, and possibly Tungsten too...

Even way less than one droplet will cause the bulb to blacken very quickly, by a mechanism called water cycle:
Close to the hot filament, the water molecule disociate due to the heat,
 the oxygen reacts with the tungsten from the filament,
then the tungsten oxide and hydrogen move to a coolder bulb wall,
there the hydrogen react with it, forming back the water and tungsten metal,
the metal then settles onto the bulb wall,
 the water eventually drifts back close to the filament
and the cycle repeats...

So it would definitely shorten the bulb life.. but it would not Explode or anything like that?

Nope it won't

The lamp may however explode from the arcing at EOL if it is not fused, but that could happen without the Water. If anything, the Water might lower the chances of arcing in the 1st place depending on the quantity

Actually if you left a droplet of water in the lamp, while pulling the vacuum it would boil off before sealing the lamp so really nothing will happen short of filling up the cold trap/cold finger dryer with ice or contaminating the oil in the vacuum pump if they don't use a cold trap, water under a vacuum will boil at room temperature, and even cooler.

Water is not much of an issue if you use a cold trap, it's the light blue liquid O2 that's a problem, and easier to produce then you would think, and in the oil, water is not a good thing and if you get enough of it you need to change it more often, or lose parts from corrosion ..

But I don't see a lamp exploding with one drop of water inside as it will be in the gas phase you'll get some oxidization of the filament and a light coating on the glass darkening it slightly, and a reduced life but nothing serious.. 

If you plug it into this plug all will be fine http://www.lighting-gallery.net/gallery/displayimage.php?album=3441&pos=4&pid=100214

Actually if you left a droplet of water in the lamp, while pulling the vacuum it would boil off before sealing the lamp so really nothing will happen short of filling up the cold trap/cold finger dryer with ice or contaminating the oil in the vacuum pump if they don't use a cold trap, water under a vacuum will boil at room temperature, and even cooler.

Water is not much of an issue if you use a cold trap, it's the light blue liquid O2 that's a problem, and easier to produce then you would think, and in the oil, water is not a good thing and if you get enough of it you need to change it more often, or lose parts from corrosion ..

But I don't see a lamp exploding with one drop of water inside as it will be in the gas phase you'll get some oxidization of the filament and a light coating on the glass darkening it slightly, and a reduced life but nothing serious.. 

If you plug it into this plug all will be fine http://www.lighting-gallery.net/gallery/displayimage.php?album=3441&pos=4&pid=100214

Interesting... I did not know water could boil at room temp... also that picture is hysterical   

A single droplet of water should be no problem for the vacuum pump at all, just because they get way more of it from a normal air humidity. Of course, the droplet boils off quite quickly once the pressure drops, but still the seemingly small amount of water vapor remaining within the bulb will kill the lamp in just few hours.
Normally incandescents do contain some form of getter to catch even the tiny amount, what may get there absorbed in the construction materials and maybe released once heated up. E.g.red phosphorus was used on the selfballasted MVs for exactly that purpose...

Yep a single drop of water is nothing for a vacuum pump, but over time it adds up, and evacuating a light you don't really need a cold trap either unless your doing commercial quantities or making freeze dried food on the side, you just need to change the oil every so many hours or you will end up losing / reducing vacuum pressure, or introducing contaminants in the item being vacuumed, or cause the pump to fail, but doing  hobbyist amounts like eclipselamps I think that's his name, you can do several lamps before needing to change the oil..

If anyone wants to try making there own lights, the rotary vane compressors in A/C's pull a pretty good vacuum and if you need to go very low you can run two or three of them in series and get pretty low, yes there is a use for old busted window ACs.. 

I dont think motors would like to work in vacuum (for the 1 or 2 compressors closest to the vacuum side). There is nothing at all to cool them down

Run till the thermal capacity of the motor body is up and switch off would allow a work for few minutes tops - is that enough for any good vacuum ?

I dont think motors would like to work in vacuum (for the 1 or 2 compressors closest to the vacuum side). There is nothing at all to cool them down

Run till the thermal capacity of the motor body is up and switch off would allow a work for few minutes tops - is that enough for any good vacuum ?

I ran two one ton (12000BTU) rotary vane window shakers one was sucking from the vacuum tank in a deep freezer (-28 C) and second was pulling from it's outlet in an attempt to make freeze dried ice cream sandwiches they ran for about 24 hours without stopping or overheating, just spinning the power meter and they where mounted outside the freezer in a room that was about 24 C above.. But if the compressor was inside a vacuum chamber it might be a problem but they are in free air so the case gets warm but that's about it..

They don't run to hard, they are just really pulling a vacuum and exhausting into free air is not that much of load, they are not compressing R-22 where you then need cooling which you get from the refrigerant in the system..

And for really long lasting freeze dried ice cream you need a dual stage freezer (-40 to -80 C)  which I don't have yet....

See the comments on this image. The issue of water in the bulb is discussed.

Interesting.. Thanks for pointing tuat out, medved said something along those lines aswell, i did not know you could make hydrogen this way

I'm curious though:  Water is H20, Hydrogen and Oxygen molecules.  So if the lamp was put under vacuum (air pumped out) wouldn't just hydrogen be left? I'm not a physicist of course.