I own a Vapalux 305 and 300X. I would like to switch out the globe for a glass fresnel lense. Has anyone ever done this? I have a boat and I would like to use the lantern + a fresnel lense at night so I can be better seen. I noticed that WWII Hasag lamps from Germany had white, green and red fresnel lenses. If spray got on the lense when it was hot would it break? Thanks!
Not sure about this but I suspect it would need to be borosilicate glass and I don't think fesnel globes were made of this. I suspect the chances of breakage from the heat are pretty high. ::Neil::
As far as I know, Fresnel lenses were made of "regular" glass. I bought a borosilicate lens for a stage light from Alibaba and it works very well with my >Continental searchlight. It did not cost much but handling fees (for customs) from the shipping company were more expensive than the lens and shipping itself. But this was a circular pane, not a cylindrical one. My searchlights (the ones with a lens) have a mica heat shield close to the mantle and a domed (?) borosilicate pane in due distance to the Fresnel lens to keep the heat away from the lens. domed borosilicate pane, see the venting holes in the light frame. Erik
Didn't those lanterns in the 'field operating theatre' sets have a tiltable lantern fitted with a Fresnel lens? Henry Plews has one, possibly with a blue-tinted lens (the lantern, not Henry). Maybe the blue was to give a 'cold' light so as not to heat up the surgical site...
David, these are neat small lenses... all regular glass. There is indeed a blue coloured globe for the HASAG 551 lanterns. These are also made from non-heat-resisting glass and break easily from the heat. Erik
Even non-borosilicate glass can stand a fair amount of heat if the heat is applied evenly. I have had the clear borosilicate glass on an Aida 214 and a Hasag 551L crack whilst pre-heating, both glasses cracked vertically where it was nearest to the spirit cup. Fortunately, I was warned that the blue glass breaks easily and so on the few occasions when I light that particular lantern, I rotate the glass during pre - heating to avoid creating a "hot-spot" which will stress the glass. So far, I have been lucky and the blue glass is still in one piece with no cracks. As far as I know, the blue glass has two purposes. 1) Apparently, blue light is more difficult to see from the air - think enemy aircraft. 2) Blue light is less harsh on the retina (a fact confirmed by those in the medical profession). The last thing anyone in severe pain wants is a bright light shining in their eyes. Henry.
The reason for blue light in military field medicine is to be able to see blood. When white light is restricted for operational reasons, the typical red light filter masks the presence of blood. Blue light shows it as a darker area, almost black. Currently, a combination of red/green light is proving to be a better filter combination for medics.
