Pasteur experiment glass tubing

[cheltie]

WE are currently doing the Pasteur experiment but are short of the S - bend glass tubing.
Does any one have any they don't want or know of a place we can buy it? I had a fairly unsuccessful go at making some - kept ending up with v bends not rounded curves. Is there a trick to this?

Hope someone can help.

Thanks, Helen.

[Robdean]

Just a thought. Rather than trying to bend the tubing why not just use a short piece of straight tubing to pass through the cork / rubber stopper and then attach a shortish piece of rubber tubing which can than be curved into a loop, securing with sticky tape or string. Works for us!

[smiley]

The trick to making U-bends is patience and time. You have to roll the tubing in the flame so it heats up all the way around fairly evenly, and then just bend it a little bit. Allow it to cool and heat up a spot about 2cm away from the first bend, and when it is hot there, then bend that bit. Cool again, then heat the section in the middle, and bend again. I usually have 3 or 4 going at once, so I can be heating and bending one piece while another is cooling. If you try to make all the bend at once it can be fairly weak.
This is very painstaking and possibly annoying, but it works. I use the time as "time out therapy" - you know "Can't talk, doing important glass-bending, get it yourself" time.

Cheers, K

[Robbie]

Hi,

It also helps if you use a batswing burner rather than a regular bunsen burner, as you can heat a longer section of glass tubing at a time.

Cheers,

Robbie

[louie]

I needed a laugh .... I'll have to remember that important glass bending technique myself regards Louie

[Loopy]

I was fortunate enough to have had the help of a lab technician to show me how to bend tubing (still wearing "L" plates)... but I never found out how to flame polish the ends of glass rods. Can anyone tell me how?
Thanks,
Lou P.

[Ian]

I was fortunate enough to have had the help of a lab technician to show me how to bend tubing (still wearing "L" plates)... but I never found out how to flame polish the ends of glass rods. Can anyone tell me how?
Thanks,
Lou P.

The flame polishing of the rods is easy enough. Just hold the end of the rod in the hopt part of the flame untill it becomes bright cherry red. If you keep it there a little linger, the end of the rod will start to slightly droop. At that time, you press the hot end of the rod onto a "heat proof mat" and that makes a nice little knob on the end of the rod which increases the stirring surface of the rod, so it stirs better, and it also helps to keep the little rubber/plastic tubing on the end from falling off.

As for the "Pasteur's Experiment", we use the straight glass tube through the cork with asingle circular loop of rubber tube attached. Works brilliantly.
regards
Ian

[Loopy]

Many thanks Ian. I love learning things, I now look forward to putting this knowledge into practise!
Cheers and beers,
Lou P.

[Mother]

Hi All
I bend all my glass tubing and have some weird and wonky 'S' bends,but they all serve the purpose they are suppose to.Doesn't worry the teachers, but the students often have a laugh about the shapes. The best way to learn how to bend tubing is to practice when you have some spare time (What's that!! I hear you ask) I actually find it very soothing to do.
Take care
Mother

[Xenon]

I make my own 'S' tubes but they can be fragile (in the hands of students and teachers). An alternative could be the plastic single-piece air-locks used for home-brew.

Xe, SD, KOPR

[cheltie]

Thanks for all that info.
I will have to try and find some "spare time" to improve my glass bending.
Helen

[Slartibartfast]

Using the very tip of the lighter blue bunsen flame (the hottest point) without rotating the tubing while heating it will give a very direct point at which you want your bend. DO NOT bend over using a heat proof mat - allow gravity to bend it to the desired angle. This gives a beautiful bend with no kinks and is internally streamlined for great steam flow in turbines.

[Sassi]

The trick to making U-bends is patience and time. You have to roll the tubing in the flame so it heats up all the way around fairly evenly, and then just bend it a little bit. Allow it to cool and heat up a spot about 2cm away from the first bend, and when it is hot there, then bend that bit. Cool again, then heat the section in the middle, and bend again. I usually have 3 or 4 going at once, so I can be heating and bending one piece while another is cooling. If you try to make all the bend at once it can be fairly weak.
This is very painstaking and possibly annoying, but it works. I use the time as "time out therapy" - you know "Can't talk, doing important glass-bending, get it yourself" time.

Cheers, K

Hi smiley,

Just been asked for the pasteur exp again and decided to try and please the teachers by trying to bend some glass tubing... Naturally I did some research first and by the looks of things it seems you know what you are doing re glass bending Please can you help me what do I need to think about and how will I know when it is heated up enough??? Please everyone help, I have no idea what I am doing here...


Sass

[J]

You will feel it start to bend when it is hot enough. Have a practice and you'll know as soon as it starts to feel soft enough to bend. Be very careful it stays hot and doesn't look hot.

J

[lada]

Like Robyn, we have used clear plastic tubing bent into a loop. It works well.
Lada

[smeee]

I have in the past used plastic tubing ( fish tank filter size ) and sticky taped it into the "S" shape.....it helps to soak tubing in hot water to make it more pliable before shaping.
Also bought from a brewers shop the plastic" airlock "- to do the same as glass tubing ( good thing is both methods don't break ! )..see attached link to give an idea of what it looks like

http://www.esbeer.com.au/category34_1.htm

[smiley]

Hey Sassi,

When bending glass, I do use a batswing burner, however, if you don't have one, an ordinary one is OK. Tips are:

Hold the glass just above the light blue cone in the centre of the bunsen flame, because that's the hottest part of the flame.

When the flame is burning orangey-red, that's hot enough to bend. Rolling it in the flame heats the tubing evenly all the way around.

Like Richard said, gravity works. If you feel the tubing sagging, you can kind of let it go, or just encourage it gently. If you force it, even just a little, the tubing kinks in the middle and blocks off the hole.

Remember!!! Glass that is no longer red-hot still IS extremely hot. I once burned a u-shaped groove in my arm (yes - literally) from brushing against a rod that "appeared" to have cooled down - but wasn't!

Don't forget, these days you can buy really groovy, and cheapo air-locks from home brew shops, and some even have corks with matching holes in them.

Good Luck.

[noona]

I also use rubber tubing make a loop and tie it up with string I then use some tape to make sure it stays put works every time.
Noona

[goody]

Go to the local home brew shop and by airlocks designed for the beer vats.
Very cheap and a great alternative to hassleing with glass tubing

[Sassi]

Afternoon everyone,


So I found one of those batswing things, put up a sign "only knock if there is a fire" and finally put the phone of the hook and sat down to bend my first glasstubing ever Well it went really well, made a few with a beautiful smooth S-bend and was really quite pleased with myself After letting them cool down I placed them in a tray and left them on MY bench. The next day my tray is mysteriously gone... it is no where to be seen and not one of the teachers knows what has happened to it... the pasteur exp was due that day so then I quickly had to make up some using rubber tubing instead. The teacher was happy so that was good, but I have spent all week looking for my little babies, I was that proud of them , well I finally found them when taking a broken test tube to the broken glass bin, I find some bits of tubing that looks mysteriously like my beautiful s-bends No one has confessed yet, but I intend to do a full scale investigation, my prime suspect is Mr B, he is such clutz But why couldn't he confess huh???

Sassi