BY FORREST M. MIMS III
Ultra-Simple Sunshine Recorders
SUNSHINE IS ESSENTIAL FOR PLANT
growth, which is one reason scientists have
developed so many methods to measure it.
In a future column I’ll show how to measure
sunshine electronically. But first, let’s enter
the MAKE time machine and zip back to 1838,
when instrument maker T.B. Jordan made the
first known automatic sunshine recorder.
Jordan wrapped a strip of silver chloride
photographic paper around a clock-driven
cylinder, and mounted it behind the mercury
column of a barometer. The photo paper
was exposed to sunlight as it rotated past an
aperture, and this provided a record of when
clouds blocked the sun. The width of the
exposed portion of the paper was controlled
by the height of the mercury. Thus the instrument was both an early barometric pressure
recorder and the first sunshine recorder.
In 1840, Jordan designed a second sunshine recorder whose photographic cylinder
was exposed to sunlight passing through
a pinhole in a second cylinder that rotated
about the photo cylinder once in 24 hours.
You can make simple versions of Jordan’s
sunshine recorders using cyanotype paper.
It’s easy to use, and its image is preserved
by simply immersing the paper in water.
Easily record sunshine
and cloud cover by using
cyanotype blueprint paper
with a film canister or
a cheap quartz clock.
and exposed to ultraviolet light. The blueprint
paper was then developed in water rendered
slightly acidic. The paper exposed to the UV
light became a rich blue, while the paper
shadowed by the drawings became white.
The blueprint process was discovered by
Sir John Herschel in 1842 and has remained
essentially unchanged ever since. Herschel
described his discovery in his paper “On the
Action of the Rays of the Solar Spectrum
on Vegetable Colors, and on Some New
Photographic Processes,” published in
Philosophical Transactions of the Royal
Society (June 1842). You can make your own
blueprint paper, or buy it from hobby and
craft stores. I use SunArt paper by TEDCO
( tedcotoys.com). It’s available in packages of
15 sheets measuring 4"× 6", 5"× 7", or 8"× 10".
The Cyanotype (Blueprint) Process
When he wasn’t flying aircraft for the U.S.
Air Force, my father was a civil engineer and
an architect. Detailed architectural drawings,
imaged on cyanotype paper and known as
blueprints, were displayed on his office walls.
Today, blueprint means a detailed plan or
a physical model of something, but originally
it meant a cyanotype print of an architectural
or engineering illustration. Blueprints were
created by first making an original drawing
on a sheet of translucent paper. This drawing
was placed over a sheet of blueprint paper
28 Make: makezine.com/26
Ultra-Simple Pinhole Camera
The simplest sunshine recorder is a light-tight
enclosure in which blueprint paper is placed
opposite a pinhole. This fits the definition of
a true camera.
Before sunrise, the recorder is mounted
in a fixed position so that the pinhole aims
at a point about halfway between solar
noon (where the sun will be at its highest
point in the sky) and the southern horizon
(northern horizon if you’re in the Southern
Hemisphere). After sunset, the recorder is