I can't bend glass tubing

I have tried repeatedly to bend glass tubing and am very frustrated. I didn’t think it was this hard.

I am using a Bunsen burner with a wingtop attachment (aka flame-spreader). My tubing is about 1/4 inch in diameter with maybe 1/16 inch thickness. I believe it is Kimex brand.

I started out holding the tube perpendicular with the flame, then read that parallel is better. I am slowly rotating it in the flame and IT WILL NOT MELT!!! :mad:

What am I doing wrong?

It’s been a while since I did it with my classes, but we never used the flame spreader. We just adjusted the burner for a good, hot flame (blue cone) and had at it. The kids used to bend the glass into very elaborate shapes quite easily.

You might be holding it in the wrong part of the flame - the tip of the inner cone is the hottest bit, I think.

What Scumpup said, use the blue hot part. I can even bend the tubing with an alcohol lamp, but it takes a lot longer.

I’m sure you know, but once the glass gets soft, you can also pull the two ends apart so it tapers down, Then when cool, break and you’ve got a couple of good pipettes.

Is it possible your tube is silica (aka quartz, fused quartz, SiO2)? Such tubing is popular for more critical applications including high temperature ones. It has to get very bright before it will bend.

I’m not sure how to tell the difference. I think silica is sufficiently harder than borosilicate glass (Kymax and Pyrex are brands of borosilicate) to scratch it.

OK! Thanks for the responses. I took the flame-spreader off and adjusted the height some and finally, it bent! Thank you! I knew someone had to know!


Burn yourself yet? That was always the inevitable result of our glass-bending sessions in college chemistry. Stuff stays hot a lot longer than you’d think. :wink:

Someone in my class bent it before it was hot enough, he wound up with hot glass shattering/spashing on him.

Most hot glass looks exactly the same as cold glass. That’s something I found out the hard way.

Quenching it in water doesn’t help, either.