Topic 25: Rubber and other exudates

Johnny-come-lately--The Brazilian rubber tree, Hevea brasiliensis, is the most recently domesticated plant of major economic importance.  It is now cultivated almost exclusively in Far East plantations, and supplies virtually all the world's natural rubber.  About half of all the rubber used is natural, the rest is synthetic and made from oil.    

Hevea was domesticated about 120 years ago, in the 1870s.  All other important economic plants were domesticated one to several thousand years ago, e.g., coffee, tea, cotton, grains, sugar cane, tobacco, potato, tomato, all the stone fruits like peach, cherry.  Modern breeding has greatly changed all these crops, with increased disease resistance and yield.  Dramatic improvements in yield have also been achieved with Hevea over the last 100 years.

 The Big Picture: Here are the five phases in rubber history :

 Phase 1:  Europe is a rubberless world; not a Rubber Ducky in sight--Before Columbus no one in Europe had ever heard of rubber, let alone rubber erasers, balls, tires, balloons, condoms, rubber bands, gloves,  or any of the other zillion useful things made of rubber.  Poor desperate Euro-trash, no wonder they wanted out. Meanwhile in Central and South America people are having a lot of fun with rubber, making balls out of it, rubber socks, syringes, idols.

 Phase 2:  Pre-manufacturing-- Columbus has landed.  But rubber has a slow arc to greatness.  For several hundred years only piddling novelties are made by Euros from the tiny quantities of rubber brought to Europe .  Rubber is collected from many species of wild Central and South American rubber plants. Some balloonists get into the act.

 Phase 3: Pre- and post vulcanization, but little demand--Many wild species including Hevea are used, but collection and export of rubber are more organized than before.  We are beyond the novelty stage.  Raincoats and other items are actually manufactured, though still on a small potatoes level.  Then the invention of vulcanization in 1839, which dramatically increased quality,  led to a sudden expansion of demand for rubber, especially from wild Hevea.  The use of rubber for waterproof clothing in the Civil War produced the first rubber boom, 1861.  Brazilian rubber is still king, but rubber regicide is imminent.

 Phase 4. Rise in demand: Hello tires, good-bye Brazil --Hevea plantations are first established in Asia toward the latter half of the 19th Century, and they begin to supply rubber in a few years.   About 1900 the amount of rubber from wild trees abruptly declines due to over-exploitation.   The Age of Rubber begins with the huge demand for automobile tires at the turn of the century.   Hevea is established as the single  source of rubber.

 Phase 5.  Emergence of synthetic rubber and its capture of 2/3 of  rubber market.  Synthetic rubber is made just before WW II, in anticipation of the Japanese capture of Far East rubber plantations, which establishes synthetic rubber as viable substitute for natural rubber.

 Once again in more detail, the five phases of rubber:

 Phase 1:  Rubber was a religious substance to the Aztecs and Mayans.  Rubber was called ulli and it symbolized the life force or blood.  Here is the principle of similarity again: A liquid that flows from a cut tree must be its life blood; never mind that we now know that latex does not circulate, carries no food or oxygen and does not resemble blood in any significant biological way.  The symbolism is what is important to the Mayans.  Latex is made in tubular cells called laticifers, and latex is the source of rubber and opium, remember?

 Rubber was burned directly, which it does very well.  We know that from all the burning cars we see exploding, just like on TV.  Rubber was also fashioned into figurines and paintings, and carried in parades at times when human sacrifices were made to propitiate the gods.

 Rubber was valuable for making rubber balls, which were  used in ceremonial ball games.  These were played in stone courts with stone rings and balls that weighed 28-30 pounds that were shot through the hoops. The game was played more like soccer. Rubber was used to pay taxes to rulers.  Rubber had a small use in local crafts, as water proofing in the Amazon, and to make bottles and syringes to use in enemas.  Others were fond of  dipping their feet in the latex and making waterproof shoes that fit perfectly.  The Aztec rubber was obtained from a tree called caouthchouc, meaning weeping wood. 

 Phase II.  Piddly uses of rubber in Europe --It took Euros a long time to catch on to rubber.  Early visitors described its use by Mayans and some brought home nifty souvenirs.  One of the early explorers interested in rubber was the French botanist,  Charles Marie de la Conamine, who collected it in 1735 .  He brought some coagulated latex back to France , where he dissolved it in turpentine.  It must have seemed like a good idea at the time.  Actually, once rubber is coagulated that is about the only way to deal with rubber.  In Europe the only way to use the rubber objects was to redissolve them, then let the solvent evaporate and leave the rubber in a new form.  And so a number of scientists from 1750 to 1800 set about discovering the best solvents.

What did Euros make out of rubber? Sir Joseph Priestly made the first erasers in 1770, giving them the name rubber. They made catheters.  If you are so lucky not to know what a catheter is: Catheters are fine tubes inserted into the urethra or through surgical wounds and used to drain off urine or fluid.  Catheters were made by dipping wax molds into a solution of latex.  Air-tight balloons were first made in France in 1783.  A rubber solution was applied to silk and the first hydrogen balloons were made.   A few patents were filed for waterproofing but nothing much was developed.

 Phase III.  Manufacture, vulcanization, and a move to the big time for rubber. 

 The first factories of the Industrial Revolution were constructed from 1800 to 1830, and they made textiles using steam driven looms.  The first rubber manufacturers were also concerned with clothing.  In 1820 Thomas Hancock made garters, rubber bands, and cushions  containing rubber for elasticity and waterproofing.  In Scotland Charles MacIntosh in 1823 patented a coal tar derived naphtha solution and glued two cloth layers together with a rubber layer in the middle to make a raincoat.  In the UK raincoats are sometimes called MacIntoshes I am told.  There were many problems with these early rubbers because they were not vulcanized.  They cracked in cold weather and became sticky in warm weather.

 The wonders of vulcanization--All of these sticky problems were solved by the introduction of vulcanization by T. Hancock and Charles Goodyear in 1839.

Goodyear actually found it  and Hancock stole it and patented it in France and England .  Vulcanization involves mixing sulfur, lead oxide and heating the mixture, which cross links the rubber molecules.  Cross linking means that separate rubber polymers get bonded together, to make them more stable to heat and pressure, and to become more elastic.  Vulcanized rubber became waterproof, heat proof, and impervious to weather and more elastic than natural rubber. 

In 1839 there was  not a huge need for rubber tires.  There were only horse drawn vehicles at this time, and very little need would arise for sixty years. Instead there were minor items, like overshoes, pulleys, hot water bottles to be made.  Rubber was still just slightly ahead of its time. 

 Phase III: Huge rise in demand, plantation rubber:

 Rubber baby buggy bumpers--Nevertheless tires were made, by Hancock, Robert Thomson, and J. Dunlop for bicycles and carriages, using cloth and rubber.  Thomson invented the pneumatic rubber tyre in 1845.  Fifty years would go by, and finally, in 1898 the automobile tire was made.  There were 4 autos registered in US in 1895.  The Ford Model T was first made in 1908, and 15 million were produced by 1927.  That works out to 60 million rubber tires--a lot of rubber. There was no synthetic rubber available then.  The US was using 50% of the world's rubber for cars in 1918.  Where was all of this rubber coming from?

  E Pluribus Unum, or one rubber source from many--Until about 1900 there were a number of plants used to make rubber.  Rubber was gathered laboriously and inefficiently from tropical rain forests of the New World and Africa .  Terrible exploitation was practiced to meet demand. Then by 1900 everything had changed, and Hevea dominated all the others.

 The rubber of commerce comes from the Brazilian rubber tree,  Hevea brasiliensis.  The trees are native from the vast flat stretches of the lower Brazilian Amazon to Peru and Bolivia .  They are huge trees, widely scattered in the forest.  Biodiversity is amazing where the rubber tree lives.  There are more kinds of trees in one square mile of this forest than in all of North America .  The scattering and low density created a problem for efficient harvesting of rubber.  During the early phase only wild trees were used, with poor management.  Everything was done wrong from the standpoint of rubber productivity, and the well-being of the laborers.  Native trees soon lost out to plantation trees.

 Why did harvesting native rubber trees quickly fail?  For many of the same reasons that harvesting native quinoa trees failed.  Harvesting of widely scattered, genetically diverse trees is very inefficient compared with plantations of highly selected, fertilized and managed trees.  This is the basic benefit of domestication and monoculture, AKA agriculture.  The downside of monoculture is increased disease damage.  

What did the native tappers do? The rubber trees were tapped by natives with cutlasses, who worked about 300 trees linked by a loop-shaped trail that started and ended at their hut home.  Their life was a very arduous one and they were essentially slaves because of deep debt.  Each tree was about 100 feet high and 6 feet around.  Each tapper had 2 groups of trees he tapped on alternate days, about 100-150 trees in each group.

 Shortly before dawn, the tapper would tap by cutting diagonal slashes in the bark, and collecting the latex into a basket. Trees were often severely wounded and succumbed to disease.  No new trees were planted.  The tapper came back to his hut with the buckets of liquid latex, and then coagulated the latex by "smoking", which meant exposing the blob at the end of a stick to a smoky fire. They made a blob on a stick by  pouring latex over a paddle and smoking, which  leads to a big ball.  After a single day's rest the trees were retapped. 

 Rubber collection was centered in  Manaus , Brazil and shipped from Para ( Belem ).  The height of the rubber boom in the late 1800s in Brazil was associated with the accumulation of great wealth in Manaus .  An opera house was built in Manaus , with exotic European woods, marble, etc., and famous Eurosingers were brought in to perform. 

 What to do?  By 1900 the Brazilian trees had been over-exploited, and supplies were not meeting demand. This was a major problem considering the huge demand for rubber, with the automobile tire about to burst on the scene. Earlier this disaster was anticipated by crafty businessmen in England .   

Before 1900 two approaches were taken to meet the anticipated demand for rubber:

 1. Exploitation of other native sources. Because prices were rising all through the late 1800s alternate sources were looked for and found.  This was a short term solution though, because the sources were non-renewable. There are a great many natural latex bearing plants, and many were sampled, which led to the large scale destruction of tropical forest resources and exploitation of gatherers in the Congo , and elsewhere.  Supplies were just not adequate in the long run, and this approach failed.

 2. Domestication of the rubber tree.  All attempts to raise rubber trees in plantations in Brazil failed because of a leaf blight, a native fungus that kept killing the trees in nurseries.  Seeds were obtained free of the fungus, and it never made it to SE Asia .  This was a long term solution.

Hevea was domesticated from 1870 to 1914.  This is one of the major events in rubber history.  In 40 years an entirely new plantation industry was formed with 2.5 million trees.  Most production was in Malaya , which was British. 

 The story goes as follows: It starts in 1870  with the intrepid Sir Clemants Markham, the same man who established cinchona plantations in Old World British colonies.  This time he suggested that rubber seed should be obtained from tropical America and plantations established in Asia in order to maintain the world's supply. Several attempts were made over a period of four years to get viable seed to England , but they failed.  

Then H. Wickham collected 70,000 seeds in the central Amazon; he was very lucky on several counts.  The rubber seeds only ripen and drop at a certain time, and for a very short period, then they die; they must be planted very soon after harvest or die; Wickham was there at just the right time to get the seeds.  It was his lucky day. 

 Wickham was not a botanist. He was a planter and rubber trader.  He had never seen a tree of Hevea brasiliensis in his life before, and there are several other species very similar to Hevea brasiliensis, which are worthless as sources of rubber.  He might have mistakenly collected them, but they were not in flower.  After collecting the seeds, Wickham was lucky enough to charter  a ship, the SS. Amazonas, which went directly to Liverpool, England, and then to Kew, where less than four percent germinated. If he had to stop along the way, probably none of the seeds would have made it.

 So, the entire rubber supply of the world depends on the fact that in 1870 Sir Henry Wickham sent 70,000 seeds from Brazil to England .  2000 germinated at Kew and they were transferred to Ceylon in miniature glasshouses called Wardian cases.  

Jebong tapping and Mad Ridley--Some of the Hevea seedlings were sent to  the Singapore   Botanical Garden , where a Brit named H. N. Ridley was stationed.  He is the next important actor of the story, because he basically developed Hevea as the best and only rubber source.  He also developed the superb Jebong tapping method, which is vastly superior to hacking tree trunks with a dull cutlass.  Ridley also got locals to grow rubber when all they wanted to grow was coffee.  They called him Mad Ridley.  He helped Malaya become the leader in world rubber production, which it still is.  Ridley died at 101.  

Beginning in about 1880: Up  with Asian rubber, languishing of Brazilian rubber--Soon  was also put into cultivation in Ceylon , and good rubber was produced in significant quantities by 1880. Time of first harvest is 6 years after planting.  Rubber was soon expanded to Malaya , Java, and Sumatra .  The climate and soils were perfect; management was good, all led to the languishing of Brazilian sources.

 What is latex anyway?   Natural rubber made from one component of latex.  Latex is a complex mixture that is found in numerous latex vessels or laticifers in the bark.  The inner bark is richer than the outer bark, so cuts must be made as close to the cambium as possible, without endangering the cambium, which is delicate.

 Latex vessels do not run vertically, but spiral at about 30 degrees. So to cut as many as possible must run from upper left to lower right.  Flow is longer and faster in the cool morning. Yields of latex are up to 1 ton per year per tree.

 Jebong tapping--This is not a dance.  It is a way to cut rubber trees.  A huge  improvement invented by Ridley was Jebong tapping, which involves a special knife that is used to cut one mm of bark off half way around the tree.  Every other day the worker cuts one mm sliver from the edge; during one year he will cut 15 cm from the bark; one side will last 10-15 years, by then new bark will have formed over the panel; Jebong tapping was not used in the wild.

 After the Asian sources came on line, the subsequent history of rubber was been turbulent: Prices went to $3.06/LB in 1910; but by 1920 dropped to $0.14/LB because of overproduction.  This led to the Stevenson plant, an agreement by rubber producers to restrict production; so prices rose to $1.23/pound; this was so high it led the Americans to look for new, cheaper sources; the Dutch were not restricted by the Stevenson trade agreement, and matched British production; British resumed production, and price fell to $0.03/LB; new trade intervention and restrictions raised the price again to $0.20/LB as the rubber producers formed a cartel.

 No more rubber from Asia --With December 7, 1941 , and subsequent invasion of Singapore , Manila , and Malaya by the Japanese, all the  Far East plantations fell to Japan ; about 0.75 of the West's supply of natural rubber was cut off; this was anticipated as early as 1939.

 Phase 5: Synthetic rubber in WW II

 Synthetic rubber--Several nations began trying to make synthetic rubber in the late 1930s, anticipating the loss of Asian sources.  By the early 1940s a stable useful synthetic rubber was found.  All of the synthetic rubbers come from oil based compounds.  It might appear that synthetic rubber has replaced natural rubber, but this is not the case.  In the last 10 years the demand for natural rubber has increased because its properties are superior to synthetic rubber.  

Use of rubber: 70% of rubber is used for tires, and 95% was synthetic, but radial tires need more resilience and need more natural rubber, so large amounts are incorporated into them; now about 30% of all rubber used is natural rubber.

Other latex products--

 Chicle and chewing gum--Nowadays chewing gum is made entirely from synthetic materials, called vinyl, like vinyl floor tile.  Formerly chewing gum was made entirely from the processed latex of a Central American tree called chicle, Manilkara zapota..   Chicle is tapped just like other latex sources, and collected and molded. Chicle was chewed by the Mayans, and later Mexicans.  Chicle is also called sapodilla, which makes a pear like fruit esteemed in the tropics.

 The chewing gum industry begins with the Mexican general Sana Ana--Our modern chewing gum industry goes back to an accidental introduction of chicle by the former president of Mexico , General Santa Anna.  He was president of Mexico 11 times, and led the troops that killed Davie Crockett and Jim Bowie at the Alamo in 1836.   During a period between exiles he was confined to a small house on Staten Island .  This was during the time when rubber sources were being search for.  Santa Anna believed he could find an investor to try to make rubber from chicle.  Santa Anna had two tons of chicle sent to NY; when he returned to Mexico he left a large amount of chicle behind with  a Mr. Adams, who was an entrepreneur and who wanted to come up with a profitable enterprise.

  Adams Chewing gum was the first--Mr. Adams tried vulcanizing chicle to make rubber, which did not work.  He tried making a dental adhesive that also did not work.  According to Adams' son's account Adams pere got the idea to make chewing gum when he was visiting a candy store and saw a child order a stick of chewing gum.  It was totally different from today's gum.  At the time it was made of sweetened paraffin, which was not very chewy.  Adams then tried using his wife's rolling pin to make chewing gum.   

Adams took the chewing gum to a nearby candy store, and it was an immediate success.  Later he added sugar flavorings and patented a chewing gum machine.  He started Adams Chicle Company.  Now chewing gum is made almost entirely from vinyl, synthetically, not from natural sources.

 Shellac--

 What is shellac and what is it for?  Shellac is a varnish, and is used for sealing and adding a shine to fine furniture and art objects.  Shellac is a resin secreted from a scale insect, Laccifer lacca, common in India and Asia .  It is a sucking insect, sucking sap from soft twigs. Laccifer feeds on a number of plants, including figs, and it makes a reddish-orange resinous secretion around itself and attaches itself to a twig. The little insect mates and the young form and emerge, go off to Rutgers , and leave the old stick behind.  The twigs are covered with encrustations, and are removed and that is called "stick lac", which is scraped off, ground and washed.  Now it is called "seed lac", which is cooked with other resins and becomes "shellac", which is used in varnishes, glazes, etc. and also as a spirit varnish.  When your spirit is very low down and dull, you can varnish it with some shellac, to spruce it up, don’t know...

 What is lacquer?  Lacquer is yet another kind of varnish.  Lacquer is made from the resinous sap of a relative of the poison ivy, Rhus vernicuflua, which is a tree in China .  No insects are needed.  Instead the bark is tapped in midsummer and the milky sap is collected.  To produce a finished article.  hundreds of coats of lacquer are applied over a period of years.  Each coat is dried and polished.  Later coats may contain metallic dusts, or mother of pearl. Check out the Metropolitan Museum some time for some amazing lacquer objects d'art.

 Copals and dammars--Copals come from wounding certain trees in the pea family, which accumulate over the cut.  They are soluble in nonpolar solvents like water, and when dry are lustrous and transparent.  They have been used in many kinds of paints and varnishes,  but today their use is practically restricted to artist's paints.  When painting with oils, colored pigment is squeezed onto a palette and then taken up in a thinning solution of linseed oil mixed with either copal or dammar.  The resins hold the paint when dry and provide the luminous depth characteristic of oil paintings;  

What is amber?  It is fossilized resin, especially of the type that now provide copal.

 Vegetable gums--Gum arabic has been used since Egyptian times, and is widely used today, in things like beer as a foaming agent.  That fine net of foam that forms on the side of a glass of beer is due to the addition of gum arabic. When you lick a postage stamp the water soluble glue is probably gum arabic.  It is used in candy to prevent crystallization, and as an emulsifier in hand lotions and many foods, like ice cream.  Gum arabic is widely used in the manufacture of ink.  The gum is almost entirely obtained from spindly wild pea trees in north Africa, which are slashed or punctured to make a wound reaction, and natives then collect dried beads of gum; it is a silent partner is people’s lives. 

 Another silent partner is gum tragacanth--It is used in mayonnaise, sandwich spreads, and milk shakes, toothpaste, hand lotions, and tablets of medicine, as an emulsifier.  Gum tragacanth comes from another member of the pea family in the Near East , a shrubby bush that is tapped with careful incisions on the root  or the larger branches.  The name tragacanth means goat horn in Greek, referring to the appearance of the ribbons of exuded gum, like the ridges on a goat’s horn.

 Turpentines are resins from conifers, also known as pitch.  They contain essential oils so they have a characteristic odor as well.  Turpentine is obtained by tapping the trees in various ways, collecting the exudate and then distilling it in stills, which produces two products:

 1. Oil of turpentine or spirits of turpentine, which rises to the top; the oil of turpentine  is drawn off.  Oil of turpentine is known as turpentine and is widely used in the paint industry because of its solvent action.

 2.  Rosin,  which remains at the bottom,  is screened and transferred to barrels and allowed to harden;  rosin is used in the manufacture of soap, varnishes, ink, plastics.  Rosin is sticky when heated and is used in the rosin bags of pitchers, and for the bows of stringed instruments, since it increases friction and intensifies the tone.  

Turpentine and pine resin were widely used to caulk wood and render ropes resistant to sea water.   So pine resin products acquired the name naval stores; it was smeared on the inside of Grecian clay wine urns to prevent leaking, and imparted a piney taste, for which the Greeks developed a fondness; so pine flavoring is added to Greek wine, retsina wine.