A Oil Painting wheel
In oil painting, making very fine lines is difficult. This is why comic books are made with water colors; ink may be applied with a pen very finely over watercolors. Pens can create very fine lines. You cannot apply ink to oil color; ink is water-based and oil paint is oil based, and they don't mix. (There may be more exotic inks, such as alcohol based, which bridge this gap.)
Generally fine lines in oil painting are made with very fine brushes, with well-thinned paint.
I found in a form a person named "The Baron" who suggested using a pizza cutter.
I have experimented with this and found that it does in fact, make maginficiently thin lines. However, it is very hard to keep the blade loaded with paint. In my experiment, I split a drinking straw with a razor blade and filled it with paint. By running the cutter repeatedly in this artificial trough, I could load it efficiently, and get about 18" or line of paint on the canvas.
You can use a palette knife to draw a sharp line; but drawing a curved line with a straight palette knife is unworkable. I curved knife might allow a curved line; but loading the curved knife is quite difficult.
Even more interesting, by holding a cotton ball loaded with paint against the back part of the wheel, I could create an even finer line.
I prpose a simple invention: A holder, like a pizza cutter, with a smaller wheel, into which a cotton ball held by manual pressure (though not with the naked hand), re-loads the wheel as it rolls, allowing a fine line to be drawn.
This would be a relatively easy to device to manufacture.
Additionally, something is needed---a mixing/loading tablet. This is probably best done as a set of grooves (one for each color to mixed) that are narrow and shallow, ending in a broader hollow for mixing. The grooves should have a length slightly longer than the circumference of the wheel. If someone wants to use a CNC machine to manufacture this for us, that would be wonderful; please contact me!
The Medium Article
To promote this project, I wrote a Medium Article which includes pictures of some paintings I made with this technique.
Here is the painting:
Here's the cutting wheel:
In response to this Article Annalee Flower Horne proposed a simple design for a "loading board" by cutting grooves and reservoirs into wood or arcylic, like this:
Annalee provided these files in Adobe illustrator format so they can be edited:
Annalee also points out that it might be easier to just use "ice stick trays" like this: https://www.amazon.com/Silicone-Ice-Cube-Sticks-Tray/dp/B01KB0XALO