<Begin Segment 5>

[Demonstration of extracting rubber from guayule]

[Cutting apart guayule plant]

GK: All right, let me cut this big branch off here. Okay, then you can start. Okay, right now I'm cutting the big branches. I'm cutting the branches so that... we don't want to deal with the leaves. Leaves do not contain any latex. So we're just gonna strip the bark which is the easiest part to extract the latex from.

So now we're just shaving the bark. Shaving the bark, this is the part that contains the most latex. The latex is trapped inside of the tiny cells, and most of it is in the bark. Some of it is in the stem as well. And the latex is also found in roots of the guayule plant. So at harvest time, if it's desired, they could dig up the entire plant and what they'll do is they'll boil off the leaves to get rid of the leaves and just process the whole plant. For this particular experiment, we're using, by the way, it's called the blender method that was developed by the Salinas Intercontinental Rubber Company. And the blender method is a very simple way to do field testing to find out how much rubber content a particular field has.

Akira Kageyama: And the rubber is right in the bark, underneath in here.

GK: Now, the tree rubber, in order to extract, get the latex from the tree rubber, all you have to do is cut a slit and the latex just, the milky sap is what is the latex. And latex is actually found in probably over 18,000 different kind of plants. It's the same kind of material that you find in poinsettia. And every time you break a leaf or a stem and the white milky sap comes out, that's latex. So latex is found in dandelions, it's found in figs, plants of the fig family has latex in it. People have actually used latex from plants like dandelions to make rubber. This is what the Russians use, a type of dandelion to extract rubber from. So guayule is a plant that is native to America that is a good source of rubber. But the plant itself is in the composite family, which is related to plants like the rose and dandelion and the sunflower, things like that. People have actually tried to hybridize, cross breed guayule with other type of composites like a sunflower. The problem is they can do the cross breeding and they can get plants, these hybrids, but they oftentimes, most often, do not produce enough rubber. But they make big plants. Okay, so all these little strips of bark will be accumulating. When we're done, we'll have a little pile of bark strips, then we'll run it into the blender.

MN: I learned something new. I didn't know poinsettia... I mean, now it makes sense 'cause it's kind of sticky.

GK: Yeah, the milky sap. Any plant that has milky sap, most of that is latex. And the milky sap or latex of plants, they serve a function. One of the functions is it's used probably to protect the plant against insects. Some of these milky saps are very, they're very irritating. I don't know if you remembered, but remember the episode of, I think it's Crocodile Dundee where he takes the saps from a plant and he... no, it was not Crocodile Dundee. The Gods Must be Crazy. Anyway, they used the sap from the plants, the guy, who's a botanist, is studying in Africa, and he shoots the tree and the tree leaks the sap onto the bad guys, and the bad guys, once the sap gets on them, that's an irritant and the guy's kind of scratching and itching.

MN: Now I know why... I had no idea that latex was in other plants like the dandelion.

GK: Yeah, it's in a lot of plants. Like I said, over 18,000 plants.

MN: And now I know why it's stickier, like you said, it's irritating. I know why.

GK: Yeah, you know like jasmine, night blooming jasmine has the white milky substance. It's very common. And also it's sticky. Now, the way guayule was discovered is that Native American Indians used to chew it, and they used to have these communal chews, and they would use the latex to make the rubber. And when Columbus discovered America, 1492, he noticed that Native American Indians were... he didn't actually land on the mainland, but in the island that he landed on, he noticed that kids were playing with this rubber ball like structure, and took samples of it back to Europe. When the European, Spanish European conquistadores came to the New World, they also noticed the rubber balls. They had a ball sport that was sort of like soccer except they had to, it was combination of soccer and basketball where they had to, without using their hands, they could use their head, shoulder and foot or hip to maneuver a rubber ball through a stone hoop which was a stone circle. They had to try to get it through that hole. So it's a stone hoop, so that made it look like basketball, but because they couldn't use their hands, made it look like soccer. But anyway, so this sport was in practice throughout Mesoamerica. And the stakes were a lot higher then, because the losing, it was either the losing team or the captain of the losing team would lose his head. And that was part of the sport. Fortunately, they don't do that today.

MN: So this is native to... I mean, Europe didn't have any rubber at the time?

GK: Well, they had rubber-producing plants, but they never made rubber. They had, they didn't know about it. So this is an invention of Mesoamerica, basically. So I know a lot of people like to give credit to all major inventions to one group or another. The Chinese invented gunpowder, fire was first developed in Africa, the use of fire, and that helped the spread of mankind to the other continents. Well, Mesoamerica can be credited for inventing the use of latex to make rubber. And they made waterproof shoes, they made waterproof other items that they could wear that was waterproof, they made waterproof containers and things like that, and rubber balls. At this time, Europe was using, they had ball sports in Europe at the time but they were not using rubber, they were using bladders and other, like pig bladders and things like that, they were inflatable. But it was a very exciting thing for the European explorers to come to the, take this new product back to the New World. And the term "rubber" was used because it was a name given to a product that was used to erase things that were written with a pencil, like an instrument, they would use a thing and they would call it "rubber," because you would rub the writing off to erase it. So that's how the term "rubber" came about. But rubber is actually made from, latex is the rubber molecules. Rubber is actually made from latex, and latex is a suspension of these polymers made up of what are called isoprene units. So isoprene is a chemical that is made by the plants, and if you polymerize it, it makes a stretchy molecule. So the molecule itself stretches. And to make rubber, what is done is you need sulfur to cross link these neoprene or isoprene polymers by cross linking it with sulfur, gives it a stronger elastic product.

<End Segment 5> - Copyright © 2012 Densho. All Rights Reserved.