Studio artists use turkey cookers to produce 18 quarts of hot water needed to initiate the black patina reactions. Although this is the fastest technique, the cold cook process will also produce black on the aluminum plates .
These steel drops will effect the color and speed of the caustic bath.
In 150F degree water for 7-14 minuets, aluminum flashing plates become very black as the steel objects promote oxidation colors on aluminum rather than acting as a resist.
Modern tintype on lightly cooked aluminum plate, archival pigment transfer,©Christine Ellinghausen.
Now our research shows that the effects can be accomplished in a warm tap water when specific mixed metals are included in the Cascade Complete bath . The reaction of the metals to each other initiates a deposit of black on the aluminum. This deposition is a natural patina , unlike applied acids.
"The aluminum plate has become completely black due to the reaction of stainless steel and copper in the Cascape Complete and the water hardening chemical cold cook bath," Bonny Lhotka.
"Water hardening chemicals promote this reaction , especially if your local water supply is soft," B.L.
These reactions can be accomplished by the use of mixed metals: stainless steel, copper and steel within the Cascade Complete solution in a naturally hard water bath.
Hard water and reactive metals promote what would be a negative result of black oxidation in commercial manufacturing. Lhotka uses this diposition on the aluminum as an abstract background for the "Modern Tintype" technique outline in her books.