<Begin Segment 7>

GK: Okay, after grinding up the guayule into little tiny chunks that make it look like coffee grounds, we placed it in the blender, and we added fifty percent ethanol, about 500 mls of that, and we added a little bit of zinc sulfate. The purpose of the zinc sulfate is that it is a sulfur compound. And what the sulfur does is it cross links the isoprene polymers, cross links them together. Because right now, they're linear molecules that are stretchy, but they're not cross linked. So the linear molecules that are isolated from one another are free to, they're suspended in water, and that's what latex is. They're suspended in aqueous cytoplasmic fluid, so it makes it fluid. But once you add the sulfur compound, what happens is that these linear polymers individually are stretchy, but they're loose and they're not stuck together. So what the sulfur does is it allows them to cross link, forms disulfide bonds. And so then we put it in a blender for approximately fifteen minutes and ran it at high speed. So now we have a solution that looks like of like, it's kind of coffee colored, it's got some bubbles in it, and if there's any latex in this solution, it should float to the top. But it'll float better if we add this solution to water. Because right now, it's harder to float in ethanol than it is water. So we're going to pour this into a beaker of water.

[Pours contents of blender into a container of water, then extracts a pulpy material and forms it into a ball and bounces it]

[Interruption]

GK: So what we did was we placed the guayule grounds, ground up guayule stems, we placed it in a solution of fifty percent ethanol with a little bit of zinc sulfate in it. And what the zinc sulfate does is it cross links the isoprene polymers. The isoprene polymers themselves are stretchy molecules. If you were to stretch an individual molecule, it would collapse back. So the property of the stretch of rubber is built into the molecule itself. But the problem with these isoprene polymers is that they are floating around freely in an aqueous solution, and that's what latex is. So the isoprene polymers in an aqueous fluid is that white milky substance that you find in a lot of different plants.

[Interruption]

GK: Okay, so we need the zinc sulfate because it has sulfur in it, and the sulfur cross links the isoprene polymers so they can form a congealed mass. And when that happens, it makes the substance more buoyant, and it'll float to the top if you pour that guayule cocktail, if you pour it in water, then the "guayule worms," they will float to the top. Normally what you would do is you would just take the guayule directly out of the vat and put the "guayule worms" in a bucket of water. And what we'll do is it will separate all the fibers that are floating in the guayule soup. And then all you have to do is press the rubber together, press it together and make a ball. And once you've done that, you have a ball. And what I usually do is I just toss it out and it just bounces on the floor.

MN: That is so awesome.

GK: Isn't it cool?

MN: Yes. How long would something like that last?

GK: Well, this is the blender method that was developed by the Intercontinental Rubber Company, and it's used for field testing only. So what they'll do is they take the shrub, they weigh it to get a wet mass weight, and then they take the rubber and they weigh it to find out what the percent rubber content of that mass that they started off with. So what we would have done here is we would have just taken the shavings of bark and we would have weighed that, because we didn't really take the rubber from the whole plant, we only took it from the bark in this case, and we would get a percent yield. And the percent yield would be something probably on the order of five percent, five to ten percent, and that's approximately.

MN: How did you test it at Manzanar? You didn't have a blender at Manzanar, did you?

AK: Yeah, we had a blender.

MN: You did the same kind of field testing?

GK: Also they had blenders.

MN: You did?

GK: I guess so. I didn't know that.

<End Segment 7> - Copyright © 2012 Densho. All Rights Reserved.