Fiber Painting

Fiber Measurements
The paint thickness on the fibers should be between 10 and 20 microns. It takes practice to achieve a consistently good layer, as the measurements from several tests show.


 * Fiber Painting Measurements
 * Paint Thickness Histogram

Fiber Pictures

 * Painted Fibers

Procedure for Painting
Wear gloves and hold the fiber in one hand while spraying on the paint with the other. It is best to paint while sitting down at the painting table rather than holding the fiber and brush at waist level. If your eyes are lined up with the paintbrush you will be able to see where the paint stream is going. Spray a little, then pause and look at the fiber. If it appears speckled with clear points (when painting a waveguide), or green points (when painting a scintillating fiber), it needs more paint. If the paint layer is covering the intended area, it still may be too thin. If you can see through it too much, it needs more paint. The paint does not have to be completely opaque, but you should have to look hard to see anything other than white.

The distance of the brush from the fiber during painting is important. Holding the brush too close to the fiber causes the paint to bead up along the edges and be too thick there. Four inches from the fiber is a good distance for spraying the paint.

To paint a long fiber, paint one short section at a time, starting at one end and working your way to the other.

Cleaning the Tube for the Paint Jar
The spray paintbrush sometimes does not spray well because of clogging somewhere. The paint can even clog the tube used to draw paint up from the jar. To avoid a blocked tube, the tube should be rinsed after use with water at an adequate pressure: as much as possible without splashing water in your eyes.

Looking at the Fiber
What you see depends on how you hold the fiber. The fibers have a square cross-section. If your line of sight is perpendicular to a face of the fiber, you may see only the paint. But holding the fiber up to the light or rotating it can make the underlying color visible. If you rotate the fiber, you can see the color on the shaded underside. Gaining familiarity with the appearance of the fiber as it is rotated may help the worker to recognize a good paint coat.

Measuring the Paint Coat
Using a micrometer to measure the paint thickness can damage the paint on a fiber. The sharp edges of the spindle and the anvil can easily scrape off paint as the the fiber is placed between them and as the screw is tightened. Putting masking tape over these sharp edges may reduce damage to the paint. To avoid scraping the paint after recording a measurement, let the fiber fall rather than holding on to it as you are loosening the screw.