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Alternative Photographic Processes - (Hand made photographic -emulsions and processes)

Lighting options for the exposure:

One of the things which is both fascinating and frustrating about alternative photographic processes that require exposure to UV as an exposure source is that there are so many variables. Different light sources work in different ways with different ways.

While the sun is appealing because of its simplicity, availability and power, it is also incredibly variable. Exposure times can vary from hour to hour, location to location etc. and it can easily be discarded as an effective source. However - with this source no electricity is required so the process can be completed in even the remotest of locations - and also it contains a complete spectrum of UV which some emulsions respond to differently than a UV lamp source.


The Ultraviolet Spectrum
Ultraviolet refers to all electromagnetic radiation with wavelengths in the range of 10 to 400 nanometers, or frequencies from 7.5E14 to 3E16 Hz.

The UVA range is wavelengths from 315 to 400 nanometers. Wavelengths from about 345 to 400 nM are used for "Blacklight" effects (causing many fluorescent objects to glow) and are usually very slightly visible if isolated from more visible wavelengths. Shorter UVA wavelengths from 315 to 345 nM are used for suntanning.

UVB refers to wavelengths from 280 to 315 nanometers. These wavelengths are more hazardous than UVA wavelengths, and are largely responsible for sunburn. The ozone layer partially blocks these wavelengths.

Strangely, UVB lasers are considered less hazardous than UVA lasers, since UVB is more easily absorbed by various fluids and tissues in the eye and cannot reach the retina in significant amounts. UVB also does not penetrate as deeply in the skin as UVA. However, the deadliest types of skin cancer (malignant melanomas) start in the epidermis, an upper layer of the skin. UVB is largely blamed for these cancers, although shorter UVA wavelengths are considered possibly cancer-causing.

UVC refers to shorter UV wavelengths, usually 200 to 280 nM. Even shorter wavelengths from 10 to 200 nM are usually considered separately as "Vacuum Ultraviolet" since they are absorbed by air, although these wavelengths are also considered a shorter range of UVC. Wavelengths in the UVC range, especially from the low 200's to about 275 nM, are especially damaging to exposed cells. Such shortwave UV is often used for germ killing purposes.


Fluorescent Blacklights
There are fluorescent tubes that emit UV. The phosphor coating on the inner surface of the tube absorbs the UVC emitted by the low pressure mercury arc, and emits longer UV wavelengths. There are at least six different UV-emitting phosphors used in fluorescent lamps.
One common lamp is the ""BLB" fluorescent lamp. The tubing is made from a very deep violet-blue glass known as "Wood's glass". The tubing is quite transparent to medium and longer UVA wavelengths, and shorter visible violet wavelengths, and a fairly broad range of infrared and the longest, least visible red wavelengths. These tubes emit lots of UV mainly between 350 and 375 nanometers, some of the 404.7 and dimmer 407.8 nM violet mercury lines, and just enough of the blue 435.8 nM mercury line to have a basically blue color when lit.
The "BLB" lamps are used for special effects due to their ability to make fluorescent objects glow very brightly.

There is a less common deep-blue-violet lamp with no phosphor and made with special glass (maybe quartz) to transmit the 253.7 nM UVC (shortwave UV) mercury line. These lamps are generally used to make fluorescent rocks glow.

There are UV fluorescent lamps with glass not dyed to block visible light. This includes the BL and the similar 350BL. These are often used to attract insects into electric insect killers. The 350BL has a broader spectrum peaking at a slightly shorter wavelength (350 nanometers) than the BL does, and is supposedly more attractive to insects than the BL.

There are other ultraviolet lamps such as UVB medicinal lamps and UVA suntanning lamps.

There are also the similar fluorescent actinic lamps, producing long UV wavelengths and/or visible violet. These are sometimes used in some special photographic and printing processes. One of these is the 03, specializing in producing visible violet light. The 03 is also used in reef aquariums with live coral since coral utilizes violet and deep blue wavelengths. The 03 actinic will cause fluorescence of most fluorescent dyes, pigments and paints other than ones which fluoresce blue.

There are a range of UV tubes that can be fitted into a standard Fluorescent fittings. These lamps are efficient and produce little heat.

Sylvania 350 black light

These tubes contain about half the UV of the Philips

Philips TLD 18W/08


Philips TLK 40 W/ 10R

Exposure box with 5 Philips TLK lamps

note the fan in the back of the box


Micro Switch on door as a safe guard turns the light off when the door is opened

Incandescent Blacklights - Edison Screw UV Lamps

These lamps are a cheaper option and easier to fit. They can simply be screwed into a house hold desk lamp. However they are less efficient, produce more heat, and the illumination is more uneven than the tubes.
There are incandescent bulbs made with deep violet-blue bulbs which largely filter out visible light. Longer UVA wavelengths get through the glass and are not blocked by the dark colored filter dye. Most visible violet and some visible blue, as well as a wide range of infrared and the longest, less visible of visible red wavelengths. Some traces of other visible wavelengths get through.
These bulbs are a convenient source of some UV to cause fluorescent paints, dyes, and other substances and objects to glow. Most of such fluorescent objects (especially magenta, red, pink, orange, yellow, and green ones) also glow from visible violet and blue light.

These bulbs are quite safe, although it may not be a good idea to stare into one from short distances for long periods of time. They generally have hotter running filaments that last only about 500 hours or so.




Theimer Strahler TH 1007 - Mercury Vapour lamp

"Beehive" (high pressure mercury) Blacklights
The high pressure mercury spectrum includes a strong cluster of lines in the 355-356 nanometer range. Fixtures with Wood's glass and ordinary mercury lamps are sometimes used as high power blacklights. Some of these fixtures are known as "beehive lamps" due to their appearance and the buzzing sound of their ballasts. Beehive lamps are available from some theatrical supply companies.




3 mm. Miniature Fluorescent Blacklights
There are now 3 mm. diameter cold cathode fluorescent miniature blacklight tubes. These come in lengths of 25, 50, and 100 mm. These are available at All Electronics, (800)-826-5432 or
Catalog numbers are UV-325 ($8.25), UV-350 ($8.50), and UV-3100 ($10.75). These apparently require only a few mA at 200 to maybe 300 volts, but substantially higher voltage may be necessary for starting.
All Electronics also sells inverters to drive these lamps and related miniature fluorescent lamps (3 to 6 mm. diameter) from 12 volts DC.
A major manufacturer of these and miniature cold cathode fluorescent lamps (CCFL) in general is JKL Lamps.

Digi-Key also sells JKL products including blacklight CCFL lamps.

Fluorescent Tanning and Medical UV Lamps
Back to UV-emitting fluorescent lamps! There is a type that emits wavelengths in the short end of the UVA range, and these are used for suntanning. One brand of these lamps is "Uvalux".
There is even a UVB emitting fluorescent lamp, used for some special medical treatments of skin. These lamps are used to confine the UV's effects to outer portions of the skin, since UVB is more readily absorbed and less penetrating than UVA is.

"RS" Reflector ("floodlamp") Sunlamps

These lamps resemble ordinary "indoor" floodlamps. They contain a high pressure mercury arc tube and a tungsten filament used as a ballast. When first started, the light is mainly incandescent light, and these lamps are sometimes mistaken at first for ordinary floodlamps. When the mercury lamp warms up, the green-bluish white color of the mercury light is more apparent. The main UV spectral lines emitted are the 365-366 nanometer UVA cluster which is nearly useless for tanning and the 313 nanometer UVB cluster. Some weaker but significant shorter UVB lines are present, as well as a weak UVA line at 334.1 nM, in the tanning range.
Since these lamps rely mainly on UVB for tanning, they are more likely to cause sunburn and skin cancer than UVA suntanning lamps (which are not completely safe either). The instructions for one of these RS lamps actually states that some sunburn is necessary in order to get a tan from such lamps. UVB lamps are also particularly irritating to downright harmful to eyes.

Other Sunlamps
There are other high pressure mercury sunlamps. Many of these are of the "Sperti" brand, and most of these have a bare arc tube made of a special glass. A few have a smaller arc tube made of quartz or a glass that is nearly pure quartz. These lamps use nichrome wire, basically heating elements, as the ballast to limit current. The larger glass arc tubes often have electrodes over an inch from the ends of the arc tube, and the ends need some of the heat from the resistive elements in order for all of the arc tube to get hot enough to fully vaporize the mercury.
Like the RS lamps, these lamps rely mainly on UVB for tanning and are quite harsh on human skin and eyes.

Exposure tests





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