Dividing the Scale
The Waterfall (a Quintone?)
In a previous section on duotones, we saw how combining 2 layers gives a printer separate control over highlights and shadows to create a longer scale. Perhaps you would want more control than that, why stop at two layers? I have made prints using 1, 2, 3, 4, or more layers at different exposures. The image to the right was printed using 5 layers of paynes gray, one for the darkest shadows, another for the shadows, the midtones, the highlights, and the brightest highlights.
As a printer it is up to you to decide how many layers you are willing to print on a normal basis. Over the years I have settled on using 3 layers, a layer for shadows, a layer for midtones, and a layer for highlights. More layers caused greater frustration and fewer layers didn't produce the quality I hoped for.
Exposure Times
Once you decide the number of layers to print, (in the following tutorials I will be using 3 layers) choose which exposure times you would like to use. In the past I have used many combinations of times ranging form 1 minute up to 30 minutes! I cannot say which exposure times will work best for you. That depends entirely on your printer's ink, your UV light source, your paper choice, and a multitude of other variables. The purpose of calibrating an inkjet negative is to neutralize all those variables and make your gum printing predictable.
To begin, find an exposure time that prints well with a single layer of emulsion. You may consider printing a few tests starting around 5 minutes, using the zones negative we created in the last section and a neutral color pigment like gray. Look for an exposure time that prints the scale centered near the mid-tones.
There are many variables that affect this time from the type of ink your printer uses, the paper you use, the light source you expose with, the exact manner you develop a print, and so forth. With my current setup, I find 4 minutes gives me a centered scale under my UV light unit. Under a sunlight exposure the time would be much shorter, probably around 2 minutes. (Don't worry about getting into the precision of seconds trying to use a specific time of say 3 minutes and 22 seconds. You will only drive yourself insane! All that matters is accuracy, not precision.)