Video Extras 2: Lost At Sea

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This video dates from before the broadband era, and as result has been heavily compressed.

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Ellen: So this should be able to make us control how quickly the rubber coagulates.

Kathy: So it’s really runny now, it’s just like milk. Enough?

Ellen: Yeah. And a lot - actually, maybe not quite so much.

Kathy: Okay.

Ellen: And a lot of this is actually just water. I really want to separate the rubber part.

Kathy: From the water?

Ellen: Yeah.

Kathy: Okay, shall I get squeezing?

Ellen: Yeah.

Kathy: So, I’m just adding an acid. I’ll add a bit and see what happens, yeah?

[SOUND OF STIRRING]

Ellen: Mmm! It’s getting thicker. Yeah. Can you tell that?

Kathy: It is, it’s like cream.

Ellen: Yeah.

Kathy: So it is coagulating.

Ellen: Mmm.

[SOUND OF STIRRING]

Kathy: Wow! That’s great.

Ellen: Do some more.

Ellen: So we can get it the exact consistency that we want.

Kathy: Okay. But we should keep on adding, to see whether we can add too much.

Ellen: Mmm. Yeah, and then we'd get a lump.

Ellen: Oh my word. [LAUGHTER] …

Kathy: No way!

Ellen: Look at this stuff!

Kathy: That’s fantastic!

Ellen: Wow! And it’s really malleable, look.

Kathy: Fantastic! Hey, that worked so quickly. That’s incredible. So we can, just before we want to coat the life jacket.

Ellen: Mmm.

Kathy: We can tip in some lemon juice. Make it really thick - as thick as we want it.

Ellen: Well 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.

Kathy: Yep.

Ellen: Wow, this is -

Kathy: That’s fantastic!

Ellen: Yeah, it’s a little bit brittle though. And that’s why we want to finish curing it so it doesn’t -

Kathy: So we can make it tougher.

Ellen: - break so easily.

Kathy: And more elastic.

Ellen: Mmm. Yeah.

[SOUND OF LIQUID BEING POURED]

Ellen: So this is the pure latex and we're going to filter a little bit of it - strain it.

Kate: So what’s the difference between latex and rubber?

Ellen: Latex is -

Kathy: That -

Ellen: Basically the milky stuff that flows in the trees.

Kate: Yeah, 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.

Ellen: No, that happens later.

Kate: Okay.

Ellen: It, it starts off and basically you have molecules, globules -

Kate: Yeah.

Ellen: - of rubber, mixed in with water.

Kate: Okay.

Kathy: And it is just like milk, it’s just held there, in an emulsion.

Kate: Wow.

Ellen: And so our goal is to get it to coagulate just enough for us to put it on the cloth and make it watertight.

Kate: So you’re going to effectively make me like a mackintosh almost!

Kathy: Yes, exactly.

Kate: Alright.

Kathy: Exactly. Now you’re going to help us.

Kate: Yeah.

Kathy: To make it coagulate. So if you just squeeze that into there.

Kate: What lemon juice will start the, the sort of... gumming up process for it?

Ellen: Lemon juice is an acid.

Kate: Right.

Ellen: And so, just a moment ago, we poured about the same amount as we poured in here.

Kate: Yeah.

Ellen: Added lemon juice - and we didn’t move fast enough!

Kathy: Now the thing is Kate:, you’ll see this isn’t really strong enough, it’s not elastic enough, it just breaks too easily.

Kate: Yeah, yeah.

Kathy: It’s not like rubber.

Kate: Yeah.

Kathy: What we’re going to do is add a bit of sulphur. Now you can just get this from garden centres and things.

Kate: Yeah.

Kathy: And the vulcanising process involves sulphur.

Kathy: What you want to do, imagine that in here there are lots and lots of molecules. Rubber molecules.

Kathy: And they’re all kinds of strands like this, waving around.

Kate: Yeah. Sort of separate strings?

Kathy: Separate strings, that’s right.

Kate: Okay.

Kathy: Now, when you vulcanise it.

Kate: Yeah.

Kathy: You cross them together and form little bridges between them and you form a net.

Kate: Oh okay.

Ellen: Like a fishing net.

Kate: Yeah.

Ellen: Very uniform.

Kathy: And that net you can kind of stretch. And then it will bounce back. Because of the little sulphur bridges.

Kate: Ahhh. Okay.

Kathy: Without the net. Those strands just come apart.

Kate: Would just, would just snap.

Kate: So this whole process is going to mean that you then have something absolutely workable and hopefully for my sake, waterproof.

Kathy: Strong, elastic, waterproof.

Ellen: Yeah, and that’s also where it will turn from this beautiful white.

Kate: Mmm-huh.

Ellen: To a more smoky, golden or even black. Because when we think of rubber we think of black.

Kate: We think of it being black.

Ellen: Yeah, that’s the vulcanisation process that causes that to happen.

Kate: Brilliant.