If the kaleidoscope is too dark, there is not enough light getting into the mirrors. Try replacing translucent pieces with transparent pieces, especially on the end of the kaleidoscope.
Rubbing cardboard along the edge of the table will make it softer and more pliable.
Narrower mirrors will create a greater kaleidoscopic effect. If you want to see the tessellation created, this is definitely better.
Experiment with different mirror systems. Create ones that have 30deg.-75deg.-75deg., 45deg.-67.5deg.-67.5deg., 90deg.-45deg.-45deg. mirror triangles, rather than just 60deg.-60deg.-60deg..
When using a canister of some type, float the stuff in colored water, vegetable oil or glycerin.
Vary the amount or the pattern of light entering the kaleidoscope.
Other Hints and Suggestions:
Simple steps to make your own kaleidoscope!
(1) Remove both ends of a Pringles potato chips can or find / buy a length of PVC pipe.

(2) Cut three pieces of mirror almost as long as your tube. The width of each mirror strip should be the same and must measure LESS than the tube's diameter. Tinker with this maybe make a cardboard model before you cut the mirror.

(3) Here is the correct pattern of overlap for mirror strips.

(4) Make a long, equilateral triangular tunnel of the mirror strips mirror surface facing the INSIDE of the tunnel. Secure the mirror tunnel by wrapping duct tape (or something similar) around the outside.

(5) Slip the mirror tunnel inside your tube. Gently pack it in place with foam rubber or something like it.

(6) Close the viewing end. Cover one end of your tube with a disc of cardboard with a viewing hole cut in the center. Secure this with glue.

(7) Now make your object chamber. Cut two disks of transparent material (glass, Lucite, Lexan, etc) to match the diameter of your tube.Next, cut a one-inch strip of lightweight cardboard a little longer than the circumference of your tube and curl it around, gluing the ends, to make a circle that matches the diameter of your tube.Let the glue set up. Now glue this to one of the transparent circles to make a little cup. Let that glue set up.

(8) Fill and close the object chamber. Find some colorful beads, bits of colored glass, costume jewelry "gems", marbles or whatever. These should be small, brightly colored and transparent.Put them in the cup (object chamber) but don't overfill.. There should be enough room for the objects to tumble around and form changing patterns. Glue the other transparent disk on top to close the chamber.

(9) When the glue has dried, attach the object chamber to the end of your tube and congratulations! You've made a kaleidoscope!
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