IN MY LAST ARTICLE (see VIEW CAMERA January/February 1994 pp. 30-33) we examined the history, chemistries, and theory associated with Platinum/Palladium printmaking. Armed with this information we are now ready to begin printing, after a brief discussion of the equipment needed for the various aspects involved in producing platinum prints.

LIGHT SOURCES
The platinum emulsion is very slow and exclusively UV sensitive enabling us to work under the light provided by yellow "bug" lights available in hardware stores, or under dim tungsten illumination. Keep any stray daylight or fluorescent light from entering the darkroom as this will cause fogging of the emulsion. The print is exposed to a light source which is high in ultraviolet wavelengths, specifically the region of the spectrum between 250 and 400 manometers. There are a number of light source options available to platinum printers including:

The Sun
The traditional platinum exposing unit. It is inexpensive, provides short printing times, but is inconsistent. This makes the printing of editions or portfolios very difficult. One of the most contrasty light sources if there are no clouds or haze.

Sun Lamps
Relatively inexpensive, exposures tend to be long, and there are possible problems from heat build up during these long exposures.

Carbon Arc
High in UV but expensive. Somewhat complicated to use as the rods burn away, the light output varies, and there is need for ventilation. Being a point source it is very contrasty.

Plate Burners
Used by the printing industry to expose printing plates. A very good light source it is contrasty with relatively short printing times but is expensive, usually on the order of thousands of dollars.

Cool White Fluorescents
Economical, consistent, but long printing times. One grade flatter than the sun or other point sources.

Fluorescent Blacklight Tubes
In my mind the best all around light source for the platinum printer. They are inexpensive, consistent, give very short printing times, and are one grade less contrasty than sunlight. My own exposing unit consists of 12 four foot blacklight tubes (F40BL) spaced 1/8th inch apart. The best negatives are fully exposed in three minutes under this unit, the light is very even, and it will handle 20 x 24 inch prints. The F40BL blacklight tubes are unshielded so UV blocking sunglasses should be worn when looking at the emitted light. Shielded tubes (F40BLB) are available but are 50% more expensive and result in exposures twice as long as the unshielded tubes. I'll wear the glasses. A very simple and inexpensive unit can be put to- gether by replacing the regular tubes with F40BL's in a 40 watt fluorescent fixture.

OTHER EQUIPMENT
Shot Glass
A small vessel is needed for mixing the components of the sensitizer prior to coating the paper. For prints up to 16 x 20 inches (which require 8 milliliters of sensitizer) a standard size shot glass is hard to beat.

Foam Brushes
These inexpensive brushes, available in most stores, are ideal for spreading the sensitizer onto the paper. Choose brushes with the smallest pore size (the ones with the wooden handles) for the most even coating with the least retention of sensitizer. Use the 1 inch brush for 4 x 5 and 5 x 7, 1 1/2 inch for 8 x 10, 2 inch for 11 x 14's, and 3 1/2 inch for 16 x 20's. This way the various size brushes will be able to absorb proportionate amounts of sensitizer for the different print sizes, so a 4 x 5 test print made with a one inch brush will be similar to the final 16 x 20 print with the 11/2 inch brush with respect to the amount of sensitizer remaining in the brush after coating. Using too large of a brush for a given print size will result in too much sensitizer being absorbed by the brush and too little sensitizer being transferred onto the paper.