Smoked glass
Encyclopedia
The term smoked glass refers to two different types of glass. It can be either of the following:
(1) Smoked glass is a flat sheet of glass
held in the smoke
of a candle
flame (or other inefficiently burning hydrocarbon
) such that one surface of the sheet of glass is covered in a layer of smoke residue. The glass is then used as a medium for recording pen traces in scientific instrument
s. The advantages of using the glass are that the recording medium is easily renewable (just re-smoke the glass), and that the trace obtained can easily be magnified by projection
onto a suitable surface. A variation on this scheme is the use of smoked paper in early seismograph
s.
(2) Smoked glass is glass manufactured with darkening materials incorporated, such that light passing through the glass is decreased in brightness
. It can be used aesthetically, for example, in the manufacture of coffee table
s with smoked glass tops. It can also be used in scientific instruments as a filter
, as in the use of smoked glass in cross-staves
and sextant
s, allowing the operator to make sun
sightings without damaging their eyesight.
Glass
Glass is an amorphous solid material. Glasses are typically brittle and optically transparent.The most familiar type of glass, used for centuries in windows and drinking vessels, is soda-lime glass, composed of about 75% silica plus Na2O, CaO, and several minor additives...
held in the smoke
Smoke
Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires , but may also be used for pest...
of a candle
Candle
A candle is a solid block or cylinder of wax with an embedded wick, which is lit to provide light, and sometimes heat.Today, most candles are made from paraffin. Candles can also be made from beeswax, soy, other plant waxes, and tallow...
flame (or other inefficiently burning hydrocarbon
Hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons from which one hydrogen atom has been removed are functional groups, called hydrocarbyls....
) such that one surface of the sheet of glass is covered in a layer of smoke residue. The glass is then used as a medium for recording pen traces in scientific instrument
Scientific instrument
A scientific instrument can be any type of equipment, machine, apparatus or device as is specifically designed, constructed and often, through trial and error, ingeniously refined to apply utmost efficiency in the utilization of well proven physical principle, relationship or technology to...
s. The advantages of using the glass are that the recording medium is easily renewable (just re-smoke the glass), and that the trace obtained can easily be magnified by projection
Image projector
An image projector is an optical device that projects an image onto a surface, commonly a projection screen.Most projectors creates an image by shining a light through a small transparent image, but some newer types of projectors can project the image directly, by using lasers...
onto a suitable surface. A variation on this scheme is the use of smoked paper in early seismograph
Seismometer
Seismometers are instruments that measure motions of the ground, including those of seismic waves generated by earthquakes, volcanic eruptions, and other seismic sources...
s.
(2) Smoked glass is glass manufactured with darkening materials incorporated, such that light passing through the glass is decreased in brightness
Brightness
Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target...
. It can be used aesthetically, for example, in the manufacture of coffee table
Coffee table
A coffee table, also called a cocktail table, is a style of long, low table which is designed to be placed in front of a sofa, to support beverages , magazines, books , and other small items to be used while sitting, such as beverage coasters. Coffee tables are usually found in the living room or...
s with smoked glass tops. It can also be used in scientific instruments as a filter
Filter (optics)
Optical filters are devices which selectively transmit light of different wavelengths, usually implemented as plane glass or plastic devices in the optical path which are either dyed in the mass or have interference coatings....
, as in the use of smoked glass in cross-staves
Jacob's staff
The Jacob's staff, also called a cross-staff, a ballastella, a fore-staff, or a balestilha is used to refer to several things. This can lead to considerable confusion unless one clarifies the purpose for the object so named...
and sextant
Sextant
A sextant is an instrument used to measure the angle between any two visible objects. Its primary use is to determine the angle between a celestial object and the horizon which is known as the altitude. Making this measurement is known as sighting the object, shooting the object, or taking a sight...
s, allowing the operator to make sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
sightings without damaging their eyesight.