Making Shades of Gray with Color Tints -
Four color inkjet printers need a light shade of gray, a medium shade, a dark shade and
black to produce a good gray scale. You can pick these numbers off the vertical scale
on the above chart. Then determine the percent of black ink in the mixture required to
achieve these grayscale percentages. Use the following formula to determine how much black
to add to the base stock.
K = P/(1-P) x Base
For example, if you need a 60% grayscale ink, then you need a 2% black mixture. Using 30 cc
of Base you want make a 2% black mixture, then the amount of black to add is
K=[.02/.98]x30 = 0.61 cc black. So the total is 30.61 cc and the percent
black is .61/30.61 = 2% and the resulting grayscale should be close to 60%.
Now add the tint. For a blue tint, mix photo cyan and photo magenta in equal parts. Add
base stock until you get the shade of blue desired. Add this blue mixture to the 2% black
mixture in steps of 10%. Swab the resulting mixture to see if it meets your requirements. If
you started with a 30 cc amount of your black ink, then add 3 cc of the blue, then swab test it.
If it is too weak, add another 3 cc and swab test again. Keep on adding the blue in 3 cc steps
until you get the look you need.
Swab Testing1 -
Use a cotton swab or Q-Tip, dip it in the ink and paint a 2 inch square on the paper you will be
printing on. You must wait for it to dry before passing judgement. Swabbing is not very accurate.
If it turns out to be too dark, then you went too far. The swab squares will be darker than what
is printed by the printer. When you think you have it right, load the ink in a cartridge and
give it a test. Use a Metering Rod
instead of a swab for more accuracy (see note 1).
Testing With a 4 Color Printer -
Paul Roark has worked out a Photoshop curve that separates the inks on a grayscale. In other
words, when you print a 21 step grayscale with this special curve, the ink from each chamber
will be easily identified and can be measured for density. This is very significant, because the
printer tends to print much lighter than swabbing.
The lower image is what the grayscale looks like after the image is converted to RGB and the
curve is applied. The zones marked C,M,Y,K are the pure inks from each chamber in the
cartridge. Normally, this is very difficult to achieve, because the Epson print driver is
mixing and blending inks from more than one chamber to achieve the requested colors. But with
Roark's curve, this is a breeze. Click here to download a
zip file containing the grayscale image and the color curve. Using this method takes the
experimental or human error out of the swabbing process.
The Toner Concept -
If you have tried the MIS VM-QUAD inks, you will know that in the yellow position the ink is
a light blue-gray tint. This blue ink is know as the "toner" ink. Using the Roark workflow
and curves for the VM-Quad inks, will produce a warm, medium warm, neutral or cool, black
and white print. These Roark curves bring in different amounts of toner to add coolness to
the print. If you put a yellow shade of ink in the toner position (yellow chamber) you can
make a sepia looking print. The Roark curves will still work to give you 4 degrees or
amounts of yellow toner, depending on which curve you use. The toner ink must have the same
density as the original VM1 toner, but it can be ANY COLOR you wish it to be. This opens the
door for all kinds of different looks, from sepia, cool, magenta, green, or literally any
tone you want.
Record Keeping -
Keeping records of your percentages and the swab results is vital. You can cut down on the
number of iterations needed by using the data from past trials. If you make one batch too
light and another too dark, then you can use your data to calculate how to make the third batch.
Without the record of what you did to make the previous batches you will be lost and you may
never be able to make the desired shade or tint or if you do you will not be able to reproduce it
again. So keep good records.
Other Shades and Tints -
If you want a warmer look, add yellow to your inks. If you want a cool look in the darker
shades and a warm look in the shadows, add blue to the darkest ink and yellow to the lightest ink.
The possibilities are endless. Don't assume your special ink mixtures and tints will translate
across several papers. Each different paper may give you surprise results. Papers and the
coatings on them have a major impact on colors and densities.
Equipment Recommendations -
Some 10 cc syringes and needles are almost a necessity. One or more for each color is a good
idea. Measuring ink using a syringe is not very accurate. We recommend getting a small
electronic gram scale. Many office supply stores sell them for postage metering. They are
also available from scientific supply houses and in some health food stores for measuring food
quantities. If you can get one that displays a tenth of a gram, then this is best. In
addition to the syringes, needles and gram scale you will need a good number of sample bottles.
The one ounce bottles are ideal for making ink samples. When you are ready to make a larger
batch, use the four ounce or pint bottles. A box of Q-Tips and a notebook to record your
results in are mandatory.
Making Curves -
This is the hard part. You will need a copy of Photoshop and a decent scanner.
If you have color management software, make sure your monitor, scanner and printer are all
profiled together. This is not mandatory, but it sure helps.
Monaco EZcolor 2 or
Praxisoft WiziWYG will do this job.
The perfect Photoshop curve will give you even 5% steps from 0% to 100% for your inkset. Load
the inks into a cartridge and print a grayscale. You can make your own, or use ours. Click
here to download the file. Just right click on the
image and save it to your hard drive. Check the RGB numbers using the Photoshop eyedropper tool.
RGB# = 255 x (1.00-P) Where P is the percent value on the grayscale. This is the basic tool
needed for making curves.
To construct a curve, change the grayscale test pattern to the RGB mode. Then go to
Image-Adjust-Curves. Modify the Red, Green and Blue curves until you can print a perfect
grayscale test pattern with the curve applied. In other words, change the Red curve, Blue
curve and Green curve. Click OK, your test image will now have color. Print the image, then
scan it. After it is scanned, use the Photoshop eyedropper tool and check the percentage steps
against the master grayscale you created above. After studying the errors, go back and
adjust the R, G, and B curves and print again. Scan it and check it. It normally takes 7 or
8 iterations to get a good curve for a new inkset. This is how Roark and others have
made the curves on our Workflow page. You could start your process by using one of their
curves that gives you close to a perfect grayscale.
For more insight on making Photoshop curves, read Dirk Hobman's article on B&W curve making,
download this file... hobman.zip.
Note (1) - Swabbing is not very scientific. The variance in the results is high. In other words, if you
swab the ink 5 times you will get 5 different results.
An alternate to swab testing is to use a Metering Rod. A metering rod, is a steel rod wound with small diameter wire.
A blob of ink is placed on a piece of paper and the rod is used to spread the ink across the paper. Because of the
uniform space between the tightly wound wire, the ink gets spread on the paper in a uniform thickness. Metering Rods
can be purchased from Diversified Enterprises.
A better method than swabbing or using a metering rod, is to use a printer
that has a black cartridge. Set the printer for black only printing. Then load a virgin empty cart with
the black ink you are testing. Print a one inch square using 720 dpi or high settings. Wait for the square
to dry, then measure the density with a Densitometer or Spectrophotometer. We use an X-Rite SwatchBook
Spectrophotometer (cost $1000 apporx). This is a much better method than swabbing and scanning. But not
all of us can afford the time and the cost of the density measuring device. The
GretagMacbeth Eye-One is the most popular instrument for making curves and profiles.
We hope this helps you get started. The process is a learning experience. We will be glad to
post anything you learn that you would like to share with others. Just drop us an email.
You will be surprised at the results you can achieve in a short period of time. Good Luck
on creating the perfect black ink set.
Below we offer the clear Base Stock for Blending Black & White inks. Do not use Eboni as the Black
Ink for blending. Original Archival Black, 7600 Light Black, or 7600 Photo Black are the acceptable black inks
for blending. Visit the Pigment Inks page to purchase a black ink or a color ink
for toning.
If you think this is a daunting project, you are probably right. Paul Roark has spent thousands of hours doing
this type of work. His ink blends are the best. There really is no need to recreate his work, he has done
a fantastic job of blending black & white inksets. Try our EZN, UT, UT2, UT7, UTFS and UTFSN inksets. You will be amazed
at the results you can get. Find your printer and inkset in the charts on the Black & White page.
This gives you all the products, papers, and workflows needed to product Gallery quality prints.
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