As one thought leads to another, and I've been reading about rubber lately, I've been wondering this: why did Goodyear, who invented vulcanisation (and hence the modern era of rubber), even think to put sulphur into rubber? Why sulphur? Seems an odd substance to try mixing with indian rubber in the vague hope something good may come of it.
Of course the mega resource of the internet would help.
Turns out the sulphur idea was actually that of another inventor, Nathaniel Hayward, and his account of his involvement in the path towards vulcanisation seems to be set out in a statement
at this obscure website:
Sometimes previous to the year 1834 there was a company formed at
Boxbury, Mass., to manufacture India Rubber goods. The members of this
company were John Haskins, Edwin M. Chaffee, and Luke Baldwin. They had
in some way learned the art of dissolving rubber gum, which they tried
to keep a profound secret. They soon, however, sold out their interest to
a larger company called the Roxbury India Rubber Company, who continued
the business in the same place. This company made large preparations to
manufacture India rubber goods, and the interest got up with regard to
this article in and around the city of Boston was very great. India
rubber cloth for carriage tops, overcoats, and other articles to protect
such as were obliged to be out in stormy weather, and it was thought
would soon come into general use and create a great demand for this
fabric.
In the year 1834 Gen. Jackson, then President of the United States,
visited New England, and while at Boston was presented with a suit of
clothes of this new manufacture, in which dress, on a day somewhat wet,
he appeared in public on horseback, for the purpose of reviewing the
troops on the Boston Common. This occurrence helped to inflate the
bubble, and in a short time the stock of this company rose from one
hundred to five or six hundred dollars a share, and every one owning
stock in this concern, it was thought, was about to make his fortune.
My
curiosity, with that of many others, was highly excited, and I went to
the factory and bought rubber cloth for a carriage top. When using the
carriage thus covered, I noticed that when two surfaces of this cloth
came together, in a warm day, they adhered, in consequence of the
softening of the gum. This struck me as quite an objection to the use of
the article, and led me to try experiments to obviate it. For this
purpose, in the month of August, 1834, among other experiments, I mixed and melted together rubber gum,
sulphur, and lampblack; but this mixture, at that time, did not result
in anything valuable. I continued, however, as I had leisure,
experimenting with this article from August, 1834 till April 1835,
showing from time to time small samples of my results to sundry persons
engaged in the rubber business, for the purpose of carrying on which
many companies were being formed in and around the city of Boston, where
I then lived. I was assured, by persons to whom I showed my samples, if
I could hit upon any method of preventing rubber cloth from becoming
soft and sticky when it was exposed to the sun or otherwise warmed, I
might depend on being well rewarded. These assurances from men in whom I
had confidence, encouraged me to continue my efforts. I therefore sold
out my livery establishment in Boston, that I might be able to devote
all my time and attention to the business of experimenting with India
rubber.
Still doesn't explain why he thought of adding sulphur at that time! However, the determination he showed to continue experimenting is pretty admirable:
After closing up my affairs, and paying my debts, I had remaining about
five hundred dollars, and a horse and buggy. With this property 1 went
out to Easton, my native town, and hired a mill building of Cyrus
Lathrop, called the Quaker Leonard Place, at a rent of one hundred and
fifty dollars a year. This mill was situated in a retired spot about
half a mile from the main road, and not far from Oliver Ames' shovel
factory. Here, remote from observation, I shut myself up and entered
upon a course of experiments with rubber, and continued it for two
months without any satisfactory result.
At the end of this time I was on the point of giving up the whole
concern, in utter despair; but finally concluded, before doing this, to
make one more trial. For this purpose I put all my chemicals, with which
I had been working, into a still of the capacity of fourteen or fifteen
gallons, with spirits of turpentine, and drew off about four gallons,
into which I put four pounds of rubber gum to be dissolved, and with
this solution, I made twelve yards (three-fourths wide) rubber cloth,
which looked finely, and which stood the weather perfectly, without
melting when exposed to the sun for months. The chemicals I put into the
still were white vitriol, blue vitriol, sugar of lead, sulphur and
several others, indeed, all I had. This result gave me much
encouragement, and I took my rubber cloth and went to Boston, thinking
that now I had found out how to make rubber goods that would stand the
test. I showed my cloth to a company recently formed called the Eagle
India Rubber Company, and they at once offered to give me employment.
But I declined entering into their service till I had ascertained, by
further trial, that I could make more cloth like the piece I had been
exhibiting. I therefore bought a new supply of chemicals and returned to Easton to repeat the experiment
which had proved so successful. To my great disappointment, after
numerous trials, variously repeated, and continued for nearly four
months, I utterly failed to make anything like the sample I showed to
the company in Boston. I then went to work to examine my chemicals
separately, with the view of ascertaining their purity. I found
impurities in many of them, especially spirits of turpentine and
lampblack. The turpentine I found I could purify by thoroughly agitating
it with water, and the lampblack by exposure to heat, and thus clearing
it of all oily matters with which it is usually connected. The spirits
of turpentine thus purified, I found would dissolve the rubber, and
purified lampblack being added, and the solution applied to cloth,
produced an article which would stand the weather. Upon the strength of
this discovery, I engaged to work for this company, on a salary of
$1,000 a year.
Finally, we get to him working out that it was the sulphur that was important:
Soon after they began work at Woburn, they expressed the wish that I
would make some white aprons, thinking they would sell well. This I
attempted to do by using a compound of white lead, magnesia and whiting,
with equal parts of virgin or white rubber, dissolved in spirits of
turpentine. The aprons looked pretty well, but when warmed would soften
and stick, and not being white enough to suit irie, I exposed them to
the fumes of sulphur to make them whiter, taking the hint from having
seen straw bonnets bleached in this manner. By this treatment the rubber
cloth became very white, and made elegant aprons. But in addition to
superior whiteness, I noticed that these aprons did not soften and
adhere after being exposed to the fumes of sulphur as they had done
before such exposure. This gave me the first intimation of the power of
sulphur to prevent rubber from becoming soft and adherent when warmed.
After this I tried exposing pieces of cloth to the sun that had been
fumigated with sulphur, and others of the same kind which had not been
thus treated, and found the former' would stand firm while the latter
would melt and become sticky.
From this time I tried a great variety of experiments with these
articles, in numerous and various combinations, and I found that only
when sulphur was one of the ingredients of the mixture, there was no
melting or sticking of the rubber cloth. All the time I was working for
the Eagle Company, and afterwards while working for myself, I, as I had
leisure, was experimenting with sulphur and rubber—and the results, and
the way and manner they were brought about I kept entirely to myself.
One of these discoveries was that rubber cloth which had been prepared
without the use of sulphur, if sprinkled over with sulphur in powder and
exposed to the sun, and afterwards washed clean, that this process
would fix the gum and prevent it from melting.
After I discovered
that it was sulphur, and nothing else, among the articles with which I
had been experimenting in combination with rubber, which prevented it
from melting and becoming adhesive when warmed, it occurred to me, that
this was what made the piece of cloth shown to. the Eagle Company free
from the usual objections to this article as then made. But during the
four months I was laboring in vain to make a perfect piece of rubber
cloth, it never entered my mind that sulphur was of any account in this business, and I did not use it.
The story goes on to explain that Charles Goodyear started sniffing around this factory, and Hayward finally told him that it was sulphur that was the secret to his non sticking rubber products.
And then, apparently, Goodyear accidentally discovered that heating it worked wonders:
He developed a nitric acid
treatment and in 1837 contracted for the manufacture by this process of
mailbags for the U.S. government, but the rubber fabric proved useless
at high temperatures.
For the next few years he worked with Nathaniel
M. Hayward (1808–65), a former employee of a rubber factory in Roxbury,
Mass., who had discovered that rubber treated with sulfur was not
sticky. Goodyear bought Hayward’s process. In 1839 he accidentally
dropped some India rubber mixed with sulfur on a hot stove and so
discovered vulcanization.
This discovery, and patenting it, did not lead to an
easy ride for Goodyear, though:
Goodyear went on to perfect the modern process of curing rubber-acid
mixture with heat, now known as vulcanisation. He received a patent for
his process on June 15, 1844. Good years, however, weren’t ahead.
Patent
wars, pirates employing his patented process without authorisation,
increasing debts (for instance, money borrowed for extravagant displays
in London and Paris) and a host of other factors meant that Goodyear
never enjoyed the success of the rubber industry. His process would go
on to make millions for others, but when he died in 1860, he was still
in debt.
Anyway, after all of that: was sulphur first being added to rubber just a case of Hayward throwing anything into the problem and seeing what (wouldn't!) stick? Seems so...
Update: I was just reading a bit about the history of sulphur more generally, and have found the next historical thing I must look up:
The element itself was not isolated until 1809, according to the Royal
Society of Chemistry, when French chemists Louis-Josef Gay-Lussac and
Louis-Jacques Thénard created a pure sample. (Gay-Lussac was known for
his research on gases, which involved him flying in hydrogen-filled
balloons more than 22,900 feet (7,000 meters) above sea level, according
to the Chemical Heritage Foundation.)
Gay-Lussac sounds well worth reading about!