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if i asked you to picture the words digital electronics or cyberspace
odds are the images that just popped into your mind are tinted a bright fluorescent green like
neo seeing the matrix for the first time indeed our collective image of digital technology is
drenched in shades of green from the strings of code the makeup software to the circuit boards
and other hardware that run said software but why green in the case of computer code the answer is
simple early computer monitors were monochrome displays based on a zinc silica phosphor known
as p1 which grows bright green such displays quickly became emblematic of the early digital
age and association has persisted to the present day when it comes to printed circuit boards
however the reason for their iconic green color is rather more complicated involving a combination
of chemistry human eyesight military requirements and plain old industry inertia it's worth pointing
out the circuit boards themselves aren't actually green at least not all of the way through printed
circuit boards or pcbs are typically made from a material called phenolic paper composed of wood
fibers mixed with phenol formaldehyde resin this material typically ranges in color from pale tan
green to dark butterscotch brown to manufacture a pcb a thin layer of copper is first bonded to the
phenolic paper substrate a resist or mask bearing the desired pattern vertical traces and component
attachment points is then screen printed onto the copper and the board is immersed in an etching
solution like ferric chloride this solution eats away all the copper not protected by the resist
leaving only the pattern of traces in older and amateur built boards electronic components are
attached by drilling holes through the board passing the component mounting pins through
the holes and soldering the pins to the copper traces on the other side modern boards however use
surface mount techniques in which the components are soldered directly to the traces this is
quicker less wasteful and allows components to be more easily mounted to both sides of the board in
older pcbs this is where the manufacturing process ended however as electronic components grew ever
smaller and circuit patterns denser a number of problems emerged for example thinner circuit
traces tended to break or oxidize easily while soldering increasingly tinier component mounting
bins often resulted in unwanted solder bridges and short circuits to correct these problems starting
in the late 1970s circuit board manufacturers began covering pcbs in a protective layer
called a solder mask and it is this layer which gives circuit boards their distinctive green color
solder masks are made of pigmented phenolic resin and like the resist in the pcb printing process
they're applied using silk screen techniques this process coats the entire board except for the
component mounting points in a thin layer of resin which is then exposed to ultraviolet light to cure
and harden this protects the circuit traces from damage and corrosion and create smaller circular
soldered dams that prevent solder from flowing from one mountain point to another but this still
doesn't answer the question of why circuit boards are traditionally colored green after all circuit
boards can be and very often are printed in a wide variety of colors from green to red yellow white
black and even purple for example boards and apple products are typically printed black while boards
in developmental products are often printed red only going green once a product reaches full scale
production similarly in many computers the motherboard is colored green to indicate its
importance while other boards are color-coded according to function yet the most popular color
for circuit boards is still far and away dark green there are many reasons for this particular
choice the main one being related to quality control in the early days circuit boards were
inspected entirely by eye and a color was needed which both maximized contrast between the board
and the circuit traces and reduced eye strain for the inspectors the raw resin used in early solder
masks was a dark honey brown and produced poor contrast with the copper circuit traces adding red
pigments caused an even lower contrast rusty color while adding blue simply yielded a darker brown
finally manufacturers hit upon a combination of blue and yellow pigments which produced a
dark green tint that met both the contrast and the eye strain criteria this binding is
consistent with the fact that human vision is most sensitive and best able to distinguish between
shades of green according to evolutionary biologists this is likely an evolutionary
holdover from our primate ancestors who needed to be able to discern between multiple shades
of green in order to navigate dense forests and jungles the widespread adoption of green as the
standard color for circuit boards was further driven by the requirement of the united states
military during the cold war a series of trials conducted in 1954 at the national materials
and procurement center in cedar bluffs virginia determined that white text on a green background
was the most legible color combination under a wide variety of lighting conditions thus when
electronics manufacturers began applying solder masks to circuit boards in the 1970s and 1980s
the military demanded they be tinted green and as the military was often these companies largest
client green became standard for civilian circuit boards as well while today's circuit boards are no
longer inspected by human eyes the white green color combination nonetheless produces maximum
optical contrast for the electronic inspection systems that are currently in use there are
other practical reasons why green circuit boards have remained the industry standard for example
other colors like black and blue are achieved using pigments containing carbon and cobalt which
being slightly conductive can potentially cause current leakage and short circuits green pigments
conversely typically contain chlorine and bromine which is far more insulating more importantly
green solder masks simply work better than other colors green is the only color of solder mask that
can consistently produce solder dams as small as 0.1 millimeters in diameter compared to red
yellow and blue at 0.12 millimeters or black and white at only 0.15 millimeters strangely however
this superior performance has almost nothing to do with the chemistry of the green pigments
themselves rather when manufacturers sought to optimize the performance of soldermask resin the
majority of research and development focused on the most commonly used formulation which for the
reasons that we just mentioned just so happened to be green so while green solder mask was originally
developed for practical reasons its absolute dominance of the electronics industry happens more
or less by accident and the industry has little incentive to change this verdant status quo in
addition to green solder masks simply performing better most circuit board assembly lines are only
equipped with a handful of solar mask application stations switching production from green to
another color or circuit board involves the laborious process of shutting down the equipment
scrubbing out all traces of the previous resin color and loading in a new resin this process
along with the short shelf life of solder mask resin results in significant production delays
materials wastage and other logistical headaches it's thus much more efficient for manufacturers
to just stick with a standard color only switching over when absolutely necessary and since circuit
boards are typically hidden away within a product casing out of sight of the end user most clients
are more than happy to stick with the ubiquitous green coloring about the only serious challenge
to green's dominance of the market is concern over environmental toxicity there's previously
mentioned the green tint of solder mask is achieved using chlorine and bromine pigments which
when burned can release toxic fumes many companies thus offer halogen free circuit boards printed in
other colors which are amusingly both green and not green at the same time however such
products remain only a small part of the market everywhere else green still reigns supreme so in
the end the answer the question why are circuit boards green is simple if it ain't broke don't
fix it and now for some bonus facts circuit boards are far from the only common objects inextricably
linked to a particular color for example have you ever wondered why barns london double decker buses
and fire hydrants are traditionally red while pencils and taxis are yellow i wonder no more
the traditional reddish hue of barns comes from early efforts to prevent the wooden structures
from rotting in wet weather starting in the 18th century farms experimented with various coatings
composed of linseed oil mixed with milk lime turpentine and other additives before hitting
upon iron oxide or rust powder which provided excellent protection against moss fungi and other
microorganisms though more modern and effective wood preservation techniques have since been
developed the tradition of painting bonds bright red continues to the present day the reason for
painting fire hydrants red is even simpler to make them more visible to firefighters and other first
responders however it might surprise you to learn that in the united states the standard color for
fire hydrants is no longer red but it's actually yellow according to the national fire protection
agency's nfpa 291 code fire hydrants must be painted factory standard chrome yellow unless
a different color has already been standardized in the community where the hydrant stands in addition
to being highly visible chrome yellow also serves to protect the hydrant from corrosion surprisingly
the colors painted on the nozzles and caps of fire hydrants also serve a practical purpose these
colors indicate the rated water flow capacity of the hydrant with red indicating less than
500 gallons per minute orange 500 to 999 gallons per minute green 1 000 to 1 499 gallons per minute
in blue 1 500 or more gallons per minute the more you know but few uses of red paint are more iconic
than on london's fleet of double-decker buses however unlike the previous examples we've
covered this distinctive livery was not chosen for reasons of corrosion protection or safety
but rather branding by the early 20th century london was served by a large number of competing
omnibus companies each with its own distinctive livery in 1908 the largest of these companies
the london general omnimus company or lgoc painted its entirely bright red in order to stand out from
the competition when lgoc was absorbed into the government-run london passenger transport board
in 1933 the red livery was adopted as standard and quickly became a british icon recognized the world
over the same standard shade of red pantone 485 c is shared by the equally iconic red telephone
boxes and raw male pillar post boxes though in these cases the color was primarily chosen for
its high visibility and not brand identity indeed prior to 1874 there was no standard
color for british post boxes with most being painted bronze green to make them unobtrusive
unfortunately they proved a little too unobtrusive for people kept walking straight into them
by 1884 every post box across the uk was repainted bright red a tradition that persists to this day
another vehicle with an iconic paint scheme is the yellow taxicab a fixture on the streets of new
york chicago and other american cities like london buses the distinctive livery originated from a
desire to stand out from the competition in 1908 albert rockwell founded a taxicab company in new
york city and decided to paint his entire fleet yellow why yellow well according to legend it
just happened to be his wife's favorite color but whatever the reason the yellow cabs proved highly
visible on the streets of new york and rockwell's business prospered changing its name in 1915 to
the yellow taxicab company that same year salesman john hurt's namesake of the modern car rental
agency founded his own tax cab company in chicago also wanting his fleet to stand out in traffic
hertz consulted a recently conducted study which revealed that yellow mixed with a bit of red was
the most visible color combination in all lighting conditions hurt his yellow cab company was also
an instant success and his vehicles and their distinct delivery were soon franchised across the
united states and last we come to perhaps the most iconic of manufactured objects the human pencil
throughout the 19th century most pencils were left unpainted to show off the quality of the wood
companies that painted their pencils usually did so to cover up imperfections and thus tended
to choose darker colours such as black or maroon however at the 1889 exposition universal in paris
czech manufacturer hardmuth pencil introduced a line of luxury pencils painted bright yellow
unlike other manufacturers hartmuth was not trying to cover up the quality of their wood but instead
advertised the source of their graphite at the time the highest quality graphite came from china
where the yellow color has long been associated with royalty happiness glory and wisdom to further
emphasize the luxury of the product hardmuth named the new line of pencils cohen or after the famous
105 carat diamond discovered in india in 1849 so successful was this branding exercise that the
company soon changed its name to cohen or hartmuth and manufacturers around the world began painting
their pencils yellow and giving them oriental names to suggest the same level of quality the
ubiquity of yellow pencils eventually resulted in the color losing its prestige status and becoming
associated with cheap consumer grade products nonetheless while pencils today are manufactured
in a whole rainbow of colors around 35 percent are still painted yellow all thanks to a clever
bit of 19th century marketing so i really hope you found today's video interesting if you did
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you