Lamina flow - test tube problem

[Boki]

Hi,

I have built a nice little lamina flow engine and it runs on alcohol burner. The problem is where the flame heats the test tube and it seems, that test tube gets soft and deformed at that spot. I use borosilicate test tubes and i am asking, if there is a better type of test tubes with better glass to be used for my engine, so that the glass stays undeformed. If there are any other solutions, please let me know.
Thank you, Boki

[Ian S C]

Boki, is it possible to use a smaller flame, use the smallest flame that the engine will run with, this will delay the break down of the test tube. Sorry can't help with sourcing more suitable test tubes.
Ian S C

[Alexandr]

The tube of quartz glass. It is used in electric heaters UFO. The melting point of more than 2000.

[Ian S C]

But can you get test tubes made of quartz glass? The borosilicate tubes are the normally used ones.
Ian S C