See my reply in the thread you started. The glass is important because, amongst other things, it retains heat around the top of the burner and keeps out cool draughts. That's essential to maintain vapourisation. I'd imagine it also promotes the correct air-flow i.e. ventilation, to provide oxygen for combustion.
As gravity fed lamps, these ones are low pressure lamps too. On gravity fed, the gravity acceleration/force maintain the pressure on the vapourizing chamber or vapourizer; on capilarity lamps, the capilarity forces are enough to rise the fuel and keep the pressure on the vapourizing chamber. Just think that trees can grow high, over 100 m some species, because osmotic pressure within roots but mainly due to capilarity. There is no pump to push the sap to the top.
Nice lamp. Torsten was a great help when I purchased my Titus. He provided me with pictures of how he made mantles for the lamp using coleman mantles. Also how to make the preheater torch. Have attached a couple of the pictures. Initially I used a nail with the end hammered out into a fork to hang the mantle on. Eventually I found by using an old veritas hard mantle I could get a pretty good light. With mine I have yet to find or build the hood and handle etc. Glass wise it has a straight glass inner and a globe outer.
It arrived days early (I love our Postal Service)! Problem: The burner assembly is snug on the threads, and I don't want to crush/scar the brass trying to turn it. (I want to see the jet so that I can ID whether it's a petrol or spirit version.) Q: Any recommendations? I don't want to contaminate the wick with penetrating fluid. A: ?
