Think all the things you knew about rubber.
Then add the properties of horn and the rich grain of exotic hardwood.
Now you’re somewhere close to the look and feel of these hard rubber sunglasses.
Introducing Ebonite; a slow-vulcanised natural rubber which derives from the ethically harvested milk-sap from Sri Lankan caoutchouc-trees.
Yep, this material is natural and boy does it have history.
It’s also great for making sunglasses.
There are two types of rubber.
Synthetic or natural.
Synthetic rubber is made from petroleum and derives from crude oil. It is drilled and bled from the earth.
Natural rubber is made from latex tree sap. It is mixed with sulphur and the organic oil from linseed. It can be vulcanised, ground down and recycled, infinitely.
You can guess which type we prefer.
But how was it discovered?
Back in the 1850’s, a young American chemist was dabbling with the composition of slow vulcanised, natural rubber. After many experimentations, he managed to produce the world’s first natural rubber thermoset which rivalled many other plastics at the time.
His name? Nelson Goodyear. (Should ring a bell.)
Ebonite had been born.
Interestingly its name stemmed from its wood-like aesthetic. Due to the prominent grain in the rubber, it mimicked the look of ebony hardwood; a luxurious, finely textured timber, also native to Sri Lanka.
This resemblance swiftly made Ebonite a popular substitute for the real and very expensive ebony wood, subsequently opening a vast array of applications otherwise dominated by the exotic timber.
Most memorably was the production of ten pin bowling balls. The rubber was extremely tough, yet had just the right ‘give’ that it was used right up to the mid 1900’s.
Other uses included wind-instrument and tobacco-pipe mouthpieces, fountain pens, car steering wheels, drinks bottle stoppers and even hockey pucks.
But never sunglasses.
World’s 1st natural rubber frame sunglasses
The Ebonite we've sourced to make these sunglasses is expertly made by a specialist factory in northern Germany.
Environmentally speaking, this material can’t have travelled any less distance as they are simply the nearest and best at what they do. There, the skilled workers extrude the material in two formats.
Rods or strips.
The rods are no use for making sunglasses as they’re thin and cylindrical. The strips however, are utterly ideal. Thick, indulgent, stable, beautiful and most of all, insanely good for machining into frame fronts.
We know this from last year’s short run. This stuff is amazing.
Considering they take three entire days to fully vulcanise the rubber, we reckon it’s worth the wait. That’s as long as we take to tumble polish them before we even begin hand-finishing, assembly and QC.
After a cumulative week of production, these polarised sunglasses are pretty damn special.
Making the rubber sunglasses
On the outside, the Ebonite isn’t much to write home about. It’s what’s on the inside that’ll blow your mind.
A charming sentiment, don’t you agree?
Beneath the crusty vulcanised exterior, the Ebonite contains beautiful swirls of toffee and rich black, reminiscent of the earliest ebony imitations. Alternating colours ‘loop’ through the length of the strip, practically identical to the lucid rings of a felled tree.
In the history of Ebonite, this is as classic as it gets.
To reveal the internal wood-grain pattern of the Ebonite, we’ve machined the material on both sides. With acetate frames, we don’t need to do this, but to get the most from this hard rubber, it’d be a travesty not to.
On the frame front, you get the incredible two-tone patterns swirling across the face. And due to the contours of the nose-pads and bridge on the back, these undulations expose the alternating layers within.
Just like wood, there’s no guessing how each will turn out.
So yea, each frame is completely unique.
In this image, you can see the end-grain of the two-tone Ebonite profiles and how similar it is to ebony hardwood. Due to the vulcanisation process, the profiles aren't completely flat which later require 'skimming' to make them uniform and square. | Image credits: Schönberger Ebonite Manufaktur
Individually machining each Ebonite sunglasses frame from the vulcanised rubber strip. Notice the rough exterior edges of the material from the vulcanisation process. | © Banton Frameworks
Tumble polishing takes 72 hours of continual rotation inside these wooden octagonal barrels. The beech media is churned around and around the frames to remove sharp edges, gently filleting them to make them smooth and comfortable to wear. | © Banton Frameworks
Hand polishing Ebonite requires 4 stages of increasingly fine compound. Each stage is progressively smoother to achieve a high-gloss and smooth grippy surface finish. | © Banton Frameworks
Schönberger Ebonite Manufaktur
SEM, the factory who make the rubber, are based in northern Germany.
From their factory floor to our workshop door, their Ebonite only travels 1,500 km. They are simply the nearest and best at what they do.
But get this; they’ve only been operating since 2006. In our books, that’s pretty damn impressive considering they make some of the most exquisite Ebonite in Europe.
Originally, the factory was built for the production of sand-lime bricks. Closed and boarded-up, it hosted 16 industrial high temperature autoclaves, previously used to bake the literal building blocks of lower Saxony, Germany.
For vulcanising their rubber, this was the perfect place.
Outside the Schönberger Ebonite Manufaktur in Hitzacker (Elbe), Germany | Image credit: Schönberger Ebonite Manufaktur
Where our rubber sunglasses begin
The factory source their raw material from Sri Lanka. Caoutchouc-trees are ethically harvested by "tapping" the natural latex which secretes from their trunks.
The latex runs freely and is collected into small bowls which are regularly emptied and poured into trays to coagulate (set) into what are called "crepes." Once cured, the crepes are washed and hung-out on large drying racks.
Clean and ready, the crepes are stacked and shipped to Germany where they are impregnated with a mixture of sulphur and linseed oil. This is the first 24-hour stage of vulcanisation inside the factory’s autoclaves.
At this stage the vulcanised rubber strips are still thin and flat. They are then finely ground into tiny particles, much the same as fine grains of sand. This is the Ebonite powder which is ready for the second mixing stage.
Using more sulphur and linseed oil, the powder is then mixed into a dough-like state which is extruded into rods and strips. Still very soft, these extrusions are then placed back into the autoclave for further vulcanisation. This can take anywhere between 24 and 72 hours.
Once hardened and fully cured, the rubber strips are sent to our workshop in the outskirts of Glasgow Scotland. They’re ready for precision machining into what we believe are the world’s first Ebonite sunglasses.
It’s a proud feeling to say that.
A plantation of caoutchouc rubber trees in Sri Lanka. Typically, these trees have a 25 year productive phase where they can consistently produce their latex-milk. In French, the name caoutchouc translates as "weeping wood" denoting the latex (sap) which secretes from the bark of the tree.
The process of collecting the natural rubber is called "tapping" where the milky-white sap is collected into galvanised cups affixed to the trunk of the caoutchouc tree. The liquid is thin and sticky containing organic polymers. Traditionally, these bowls were made from the half shells of coconuts and suspended from twine or metal wire.
The angled incision into the bark of the caoutchouc tree creates a "helter skelter" gravity flow of the latex sap. These cuts are made with a hatchet by skilled workers known as "tappers" who regularly collect the latex. See above, it trickles down and around the edge of the cut in a steady flow into the collection bowls below.
These are the cured sheets of natural rubber called "crepes." They are cleaned from impurities and then hung to naturally air-dry on these large racks. Once fully cured, they are then stacked and shipped to Germany for vulcanising into Ebonite.