Australia's Science Forum

I have some chipped pyrex test tubes left on the bench with a note to repair them.....do I just hold the chip in the blue flame to take the sharpness off the edge? thankyou

Yes that is the way to go.

thank you Labbie, I had a go, they take quite a bit and its still pretty obviously, does that seem right?

Try a hotter flame, yellow, that may be quicker.

Seriously just put them in the broken glass bin. They are damaged, broken, don't fix them. Bin them. Just get rid of them. Tell whoever left them that they are unrepairable. What were they thinking asking you to do that. If you have the Risk Assess program online it specifically says to discard any test tubes that are damaged. Or any other damaged glassware for that matter. If your repair work fails whose fault will it be? Say hello glass bin, goodbye test tubes.

I have to agree with Lyn .
Although I have fixed many a test tube , beaker and measuring cylinder that is chipped, its justvnot really worth the bother . They are so cheap in bulk ... especially test tubes .

But Labbie is on the money . More heat will help melt the glass and dull the edge .

Thank you for the replies
Bin them would be my decision too. There are about 20 in the bin already that have their bottom broken out and about thirty with chipped rims in the container for me to fix. who has the time for this??

The only chipped rims that I have fixed has been on Burettes which are $20 + to replace
With test tubes, the cost time wise to fix is way dearer then a replacement test tube

Yes it was a bit of a rant. One of those days. If your budget is so desperate that you are being asked to do this then my other suggestion is that your science department invests in a MEKER burner. This will produce a much stronger heating surface than an ordinary Bunsen burner. This type of burner will anneal the ends of cut glass rods very nicely. Also good for making bent glass tubing. Just don't hold anything in the flame too long as it will make the glass extremely soft to the point where the glass melts too much and becomes unmanageable.
However that container with the thirty chipped rims - OOPS - what a shame that it accidentally fell on the floor.

I always repair chips on test tubes to take the sharp bits off. Anything that saves resources affects our impact on the planet.

Hi Lyn,

I use a regular bunsen & flame spreader, but it can take a while to heat the glass tubing up enough to manipulate it. I have a Meker burner in the cupboard and am curious to try it. Is it still best to use a flame spreader with it and if so, where would I buy one to fit?

Thanks,
Kyla

Think they are called bat wings?

I just use the Meker burner as it is. Just sit it on a heat mat and rotate the glass rods over the top of the flame until it gets red hot and then gently roll it on the heat mat and try to squash the end a little while the glass is still pliable. Take extreme care when doing this as you don't want the glass to snap and you don't want to get burnt. I use gloves designed for handling hot glassware or leather garden gloves. Don't forget your safety glasses either.
Just use the same process for tubing. Rotating the tube over the hot flame until it gets red and then bending it using pliers. It should work. I haven't done a lot of glass tube bending so there might be someone out there with further and better advice.

Thanks Lyn!

I had a chance to try it today, as I had to make some swan necks anyway.
The Meker burner is definitely hotter and great for smoothing off the sharp ends of the tubing.
Without a flame spreader however, I found it a bit hard to heat up a large enough portion of the tubing at once. So my swan necks turned out quite angular, rather than having wide and smooth bends like normal (if that makes sense).
The higher temps will be great for quick glass repairs though, thanks