glass tube

Commercial tubes are normally melted shut with a lampworking torch. The easiest way to do it would be to carefully clean the end of the tube inside, with cotton swabs and alcohol for example, then fill the end with

100% silicone sealant (also sold as tub caulk) so you are making your own stopper glued in place.

Hi. My husband is a kaleidoscope collector and knows several artists. He runs a group with many artists as members who are willing to share their knowledge....

This may help:

said someone is currently doing the same thing you are attempting and it has been a topic of conversation. Janet R

If the tube is filled with a liquid, how do they melt the tube and avoid boiling the liquid at the same time? I know the thermal conductivity of glass is low, but I'm thinking of trying to solder a copper pipe that has standing water in it--it can't be done. Perhaps the analogy is so imperfect as to just be misleading.... Obviously is *is* done!

Mike Beede

Having done - and redone - some very bad joints in copper tubing - I agree. Glass, however, has a much lower conductivity and is normally melted with a much hotter flame - so the flame can come in, melt, quick twist and pull, melt the pull tip. Obviously depends on the glass quality and thickness and the nature of the liquid. In comparison (only), you could hold a boro glass tube a few inches from the melt point, pass it into the flame and pull a point - lamp workers do it all the time. With copper, you would burn your hand before you could think about it.

It occured to me that one trick I had forgotten about is that a glass worker can pull a tubular point (shape like a hypodermic) and heat the body of the tube gently (i.e. not red hot) and then set it in liquid and the cooling air will suck in the liquid. This may have to be repeated to fill. Then the point can be sealed very quickly because it has thin glass and a very small area to fill.