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Video Extras 2: Lost At Sea Transcript

 
Ellen and Kathy making rubber
Ellen and Kathy making rubber

Better latex than ever

How do you make a life-jacket out of kapok, rubber and the chemical process of vulcanisation? Find out more about rubber and vulcanisation.

Follow Ellen as she collects latex and makes rubber, as part of the BBC/OU's programme website for Rough Science 5

EllenSo this should be able to make us control how quickly the rubber coagulates.
KathySo it’s really runny now, it’s just like milk. Enough?
EllenYeah. And a lot - actually, maybe not quite so much.
KathyOkay.
EllenAnd a lot of this is actually just water. I really want to separate the rubber part.
KathyFrom the water?
EllenYeah.
KathyOkay, shall I get squeezing?
EllenYeah.
KathySo, I’m just adding an acid. I’ll add a bit and see what happens, yeah?
[SOUND OF STIRRING]
EllenMmm! It’s getting thicker. Yeah. Can you tell that?
KathyIt is, it’s like cream.
EllenYeah.
KathySo it is coagulating.
EllenMmm.
[SOUND OF STIRRING]
KathyWow! That’s great.
EllenDo some more.
EllenSo we can get it the exact consistency that we want.
KathyOkay. But we should keep on adding, to see whether we can add too much.
EllenMmm. Yeah, and then we'd get a lump.
EllenOh my word. [LAUGHTER] …
KathyNo way!
EllenLook at this stuff!
KathyThat’s fantastic!
EllenWow! And it’s really malleable, look.
KathyFantastic! Hey, that worked so quickly. That’s incredible. So we can, just before we want to coat the life jacket.
EllenMmm.
KathyWe can tip in some lemon juice. Make it really thick - as thick as we want it.
EllenWell actually don’t we want to, tip in some lemon juice, make it begin to get thick, dip it really fast, and then let it coagulate on there.
KathyYep.
EllenWow, this is -
KathyThat’s fantastic!
EllenYeah, it’s a little bit brittle though. And that’s why we want to finish curing it so it doesn’t -
KathySo we can make it tougher.
Ellen- break so easily.
KathyAnd more elastic.
EllenMmm. Yeah.
[SOUND OF LIQUID BEING POURED]
EllenSo this is the pure latex and we're going to filter a little bit of it - strain it.
KateSo what’s the difference between latex and rubber?
EllenLatex is -
KathyThat -
EllenBasically the milky stuff that flows in the trees.
KateYeah, because that’s what I was expecting. When you said you were going to get rubber, I was expecting that you come back with something black.
EllenNo, that happens later.
KateOkay.
EllenIt, it starts off and basically you have molecules, globules -
KateYeah.
Ellen- of rubber, mixed in with water.
KateOkay.
KathyAnd it is just like milk, it’s just held there, in an emulsion.
KateWow.
EllenAnd so our goal is to get it to coagulate just enough for us to put it on the cloth and make it watertight.
KateSo you’re going to effectively make me like a mackintosh almost!
KathyYes, exactly.
KateAlright.
KathyExactly. Now you’re going to help us.
KateYeah.
KathyTo make it coagulate. So if you just squeeze that into there.
KateWhat lemon juice will start the, the sort of... gumming up process for it?
EllenLemon juice is an acid.
KateRight.
EllenAnd so, just a moment ago, we poured about the same amount as we poured in here.
KateYeah.
EllenAdded lemon juice - and we didn’t move fast enough!
KathyNow the thing is Kate, you’ll see this isn’t really strong enough, it’s not elastic enough, it just breaks too easily.
KateYeah, yeah.
KathyIt’s not like rubber.
KateYeah.
KathyWhat we’re going to do is add a bit of sulphur. Now you can just get this from garden centres and things.
KateYeah.
KathyAnd the vulcanising process involves sulphur.
KathyWhat you want to do, imagine that in here there are lots and lots of molecules. Rubber molecules.
KathyAnd they’re all kinds of strands like this, waving around.
KateYeah. Sort of separate strings?
KathySeparate strings, that’s right.
KateOkay.
KathyNow, when you vulcanise it.
KateYeah.
KathyYou cross them together and form little bridges between them and you form a net.
KateOh okay.
EllenLike a fishing net.
KateYeah.
EllenVery uniform.
KathyAnd that net you can kind of stretch. And then it will bounce back. Because of the little sulphur bridges.
KateAhhh. Okay.
KathyWithout the net. Those strands just come apart.
KateWould just, would just snap.
KateSo this whole process is going to mean that you then have something absolutely workable and hopefully for my sake, waterproof.
KathyStrong, elastic, waterproof.
EllenYeah, and that’s also where it will turn from this beautiful white.
KateMmm-huh.
EllenTo a more smoky, golden or even black. Because when we think of rubber we think of black.
KateWe think of it being black.
EllenYeah, that’s the vulcanisation process that causes that to happen.
KateBrilliant.

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Content last updated: 18/02/2005

 

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