#18 Color overprinting magic

This is an esoteric design adventure never told until now.

I was printing a cheap but attention-getting packaging insert. One-color Pantone 485 on Wausau AstroBright Solar Yellow, 24lb wt. When I picked up the job, the red ink really popped. PMS 485 was a favorite color. I knew it well. I’d never seen it so bright when printed on white stock.

I asked Fred, the printer, “How come is this red so bright? Did you do a double hit?”

“Nope,” he said, “Red always does that when printed on yellow paper.”


“Press inks are transparent. The yellow underneath is giving it a boost.”

Pantone 485 spot color, when translated into CMYK, gives the following percentage values: C0, M100, Y91, K0. Magenta is 100% and Yellow is 91%. When you print 485
over a 100% yellow paper, it boosts the yellow from 91% to 100%.

This revealed a form of transparent color math that could be performed using CMYK.

So what would the results be if you excluded black and used 100% yellow paper (Astrobright)? Could you print a broad palette of colors with just varying percentages or tints of cyan and magenta inks? I had to try it.

Here’s the result:

Yellow overprint palette with Cyan and Magenta (2-colors only).

The first joyous discovery was that 90% Magenta and 90% Cyan printed on 100% yellow produced a warm black. I then sampled each of the colors in the grid and found out what their Pantone equivalent was.

I had built an HTML Reverse Thematic Color Lookup based on the 2,000 Pantone colors used in the paperback book, Pantone’s Guide to Communicating with Color by Leatrice Eisemann (2000).

The book is out of print but available used for $6.63 on Amazon. I looked up all the Pantone colors from the grid and found that 5 themes could be generated.

5 color themes from Cyan-Magenta overprint on Yellow paper.

Here is one of the sample sheets showing the dominant, subordinate, and accent colors for the Spicy theme:

Spicy themes from yellow paper.

I then convinced a pro bono job (free design) to let me print a donation form using CM over Yellow to see how it would work:

Donation Form for the Humane Society.

There are two colors you cannot print with this method: blue and white. But the palette would work great for say a Cinco de Mayo event, or a Mexican restaurant menu, etc. It needs to match the event theme. In my case, it didn’t but was still well received as a donation of labor.

With the advent and popularity of direct-to-plate full-color digital printing, the advantages of 2-color printing were soon lost.

So I put all of this info in the back of my mind and went my way designing full-color stuff for laser or digital output.

You’d think that would be the end of this overprinting story. But there’s more.

A client had a sensor that measured soil moisture. A competitor had reverse-engineered it and it looked identical. It was the standard green circuit board coated with a transparent green silkscreen solder-mask and white opaque ink text. They wanted to know if I could do anything creative to differentiate their product line starting with their new double-bladed sensor. The solder-mask had to be 100% coverage to prevent circuit corrosion.

Here’s the original sensor:

Original sensor design.

My research of solder-mask inks was dismal – almost all of the transparent colors were shades of green. Except for one blue, one red, and one yellow. In the opaque inks, there was black and white.

The transparent red was Pantone 485!

I asked the circuit board manufacturer if they had yellow substrates instead of green. He said it would be a special order but not a problem.

I did a mock up design in Photoshop for presentation.

Photoshop prototype mockup.

It went to committee. It took many months for approval. But this was the color strategy. Use a yellow substrate. Overprint 100% in transparent red 485 for a sealant. It would get a color boost from the yellow. Then spot overprint in opaque black. And then one more pass of color for opaque white lettering. They were frightened by how much it might cost to produce the product with so much silk-screening.

The selling price was estimated to be $150. Product costs were never revealed to me but I’d estimate them to be around $15 to $25. The extra silk-screening added $0.33 to the cost of each unit. They were delighted and realized they had done a brilliant job! I got paid but never thanked for that contribution. Lesson learned. Charge more if they don’t thank you!

Here’s the real-life final product photography:

Final product. Sold like hot cakes for $150 each.


Color by overprinting: A complete guidebook in the art and printing techniques employing transparent inks in multiple combinations.
Donald Edwin Cooke (Author)
used $394.06
Hardcover: 250 pages
Publisher: Winston; 1st edition (1955)