I applied two different spitbite mixtures in combination with Z-Acyrl as an aquatint. The first was a combination of half a cup of 42° Baume Ferric Chloride taken directly from our vertical etching tank mixed with a quarter of a teaspoon gum arabic to prevent beading. The second mixture is a premixed studio spit bite which consists of 42° Baume Ferric Chloride and a quarter of a teaspoon gum arabic. The studio mixture is recycled back into the bottle and frequently reused. Additionally I am applying a Z-Acryl hard ground through an Paasche airbrush on the finest setting. I am determining the effectiveness of the fresh spitbite mixture vs. the studio spitbite mix and the correct application amount of Z-Acryl so that the spitbite does not cause foul biting.
Date: June 16, 2010
Researcher’s Name: Olya Alekseeva
Plate Material: .032 Copper
Plate Size: 4 in x 6 in
Room Temperature: 76° Cloudy
Each plate was degreased with soy sauce that was rubbed onto the copper plate using a piece of rolled felt, rinsed and then dried with a clean rag and blow dryer. A basic airbrush sprayed aquatint was applied to each test plate in 21 rounds (see Basic Ground Applications). In each case the airbrush was opened only a small amount to allow for the finest spray possible, and each plate was sprayed from a distance of 16-18 inches away.
Plate one was etched with a mixture of gum arabic and 42° Baume Ferric taken from the etching tank. Plate two was etched with the shop mix spit bite.
Timed Application of Mordant
See diagram below on etching times.
Removal of Grounds
The grounds were effectively removed using a stripper bath of Arm & Hammer Washing Soda and water (100 grams/1 liter). The copper plate was rinsed in water and deoxidized in the brightener bath made of distilled white vinegar and salt (1 gallon/1 cup). Immediately following the brightener bath they were dried with a clean rag and blow dryer.
After Bath Evaluation
The aquatint has stayed on the plate through etching.
The ink used was a mixture of 50% Graphic Chemical Bone Black and 50% Charbonnel RSR, plus ½ teaspoon of #3 plate oil (to about 2 tablespoons ink). The ink was carded on the copper plates with mat board scraps, wiped with used tarlatan, and then palm wiped.
Paper Type: Hahnemule Copperplate
Paper Soaking Time: 3 Hours
Press Blanket Setup: Sizing catcher and pusher, 11.5 pressure, Small Takach Press
The prints lacked tonal definition because the copper plates where not properly degreased and the aquatint was oversprayed.