A ruling pen is a special pen that resembles a pair of tweezers, with a tapered tip and a thumbscrew. Graphic artists and draftsmen use ruling pens to draw fine lines in ink. You can mount a ruling pen in a bow compass to draw precise circles. Although computers now do most of the drawing for drafting and graphic design, many artists still find satisfaction in using hand tools such as bow compasses and ruling pens.
Prepare your tools. A ruling pen works by capillary action. As the tip of the pen touches the paper, the ink will start to flow, creating a fine, precise line. Make sure all surfaces, including your hands, are dry and free from oils. India ink requires a clean, smooth surface such as tracing paper, acetate, hot-pressed watercolour paper or illustration board.
Tape your paper securely to your drawing board. Some artists prefer a hard drawing surface, while others like to add resiliency by using a vinyl drawing board cover or a few sheets of softer paper under the drawing paper. Angle the drawing board comfortably so that you can move your arm freely over the surface without scuffing or cramping.
Practice freehand drawing. Use the dropper in the ink bottle to place a small drop of ink between the blades of the ruling pen. Hold the ruling pen upright, and practice making a few freehand lines on a piece of scrap paper. Tighten or loosen the thumbscrew in small steps to adjust the line width. Practice your lines until you can draw smoothly and steadily, with just enough pressure to release the ink without blotting or scoring the paper.
Practice compass drawing. Attach the ruling pen to the compass, and adjust the compass to the radius of the circles you will be drawing. On scrap paper, practice a few circles using the technique you learnt in the previous step.
Use the hard drafting pencil to make a light sketch on your drawing paper as a guide for your design. As with the ruling pen, avoid scoring the paper with excessive pressure, and take care not to leave fingerprints.
Clean and reload your ruling pen, and begin drawing your circles. Allow enough time for the ink to dry before going back over any lines, and take care not to smudge your drawing. You can fix some smudges by carefully scraping the dried ink away with a razor knife, but it's better to avoid blots and smudges in the first place. After your drawing is completely dry, carefully erase the pencil lines.
Do not dip the ruling pen into the ink bottle, or the ink will run out and spoil your drawing. A slow, steady hand creates the best lines. India ink works best when fresh. Discard ink that has thickened or separated. Experiment with other liquid media, such as liquid acrylics, well-thinned gouache or other drawing and writing inks. If the ink blots or runs too fast, clean and dry your pen thoroughly, and try again. Use opaque white ink or gouache and an extra-fine paintbrush to cover mistakes. Some art supply dealers sell correction fluid that is tinted to match popular brands of watercolour paper.
India ink can permanently stain clothing, furniture and floors. Take care to avoid spills, and clean up messes quickly. Never let the ink dry up in the pen. Rough cleansers can ruin the pen tip.