[Garth Herrick]

Hi Allan,

What a clever and well crafted proportional mixing device you have made. It should work well for your purposes.

I used a similar method last year to mix up 50 shades of gray (adding pure white and pure black to the grays makes a total of 52 value levels). After much experimentation with every brand of paint, and several different white pigments, I chose to use only Old Holland Titanium White, and Old Holland Ivory Black. Old Holland apparently makes the only commercial Titanium White that has nothing else (like Zinc) added to dilute it. This I found to be very important for my purposes of scientific control. Marvin Mattelson has pointed out that the cool gray mixes that I get with just black and white are not useful for his purposes of having warm grays to mix with his colors. He is absolutely right, but this was not my purpose. What I am doing is simply having a gray value index that is virtually calibrated with corresponding values within Photoshop, as a tool for rendering correct values from a computer reference image. These gray values make up a scale that is archived in tubes of paint fo give me consistent results even in the years ahead in the studio.

I found the old Holland Titanium White and Ivory Black to be of roughly equal tinting strength, which was very useful for formulating relationships in pigment proportions. I tried flake white, which yields a more pleasant warmer gray, but I found that I had to multiply the white proportion by a factor of seven (!) with Flake White to equal the tinting strength of Titanium White. So choose your whites carefully.

Another thing I discovered is that there is not a linear relationship in pigment proportions when mixing to match values in photoshop. One must empirically find the right warp in the proportions, especially as one approaches the outer ends of the value scale. This you may need to discover for yourself, Allan. You may find yourself favoring slightly off number relationships like 1.35:36, 1.83:35, etc. But you can do this with care with your device.

You are probably curious how I mixed 50 gray values with great control. It was basically the same method and technique you are proposing. I had a plastic pastel tray, with individual slots measuring 12mm, by 12mm, by 100mm in length. I had a palette knife with a rectangular blade 12mm wide and a flat end. I used one slot for the black and another for the white, and they were separated a bit just to keep things neat and tidy. I had all the formulations calculated out and pre-measured in a list on a piece of paper. My proportional formulas are too complex to share here. Using a ruled scale, I determined where to place the palette knife as a stop, just like your method. When all was measured, I scooped all the paint out and mixed it thoroughly on a glass plate.

I used the small 12 ml tubes. To fill them, I used a palette knife to place the paint within the tubes, periodically tapping the tubes against a hard surface to allow the paint scoops to settle within the tubes and displace the air pockets. This takes much practice, but eventually the tubed paint is neatly produced.

I hope this helps! Good luck with your investigative color scales project.

Garth