Menu Close

Kirschmann Coaxial Colour Wheel


A sturdy wooden box contains a rectangular steel instrument, a broken glass wheel, seven metal wheels, four square wooden spacers, two loops of cord, an additional length of cord, and several smaller loose parts (screws, nuts, and cardboard washers).

The instrument is a black anodized steel rectangle 25 cm x 10.4 cm. Its longer sides are bordered by walls of the same material which are 1.5 cm tall. The surface of the instrument features two rotating axles located towards opposite sides of the instrument, arranged on the centre line of the instrument’s face. The right axle supports two concentric circular pulleys of 5.8 cm in outside diameter. These may be spun using a handle attached to the topmost pulley. The left axle is set in a circular cut-out in the instruments face. This is a vertical spindle with a threaded inner hollow onto which may be placed a machined pulley/ spindle of approximately 1.5 cm in outside diameter. The glass coloured disc would have been placed on this pulley/ spindle in such a way that the pulley/ spindle and glass wheel would have been spun by the lowermost of the pulleys on the right axle using a loop of cord. One of the steel disks would have been mounted above the glass disc on the pulley spindle. The integrated pulley on the steel disk would have been attached to the upper pulley on the right axle by a second loop of cord. The two wheels mounted on the pulley/ spindle were secured by a screw in the threaded hole inside the vertical spindle.

The glass wheel (now shattered) originally consisted of two glass plates approximately 9.5 cm in outside diameter. Between these plates are sandwiched segments of transparent coloured gelatin sheet in such a way that they cover the entire inside surface of the glass plates. Each piece tapers from the edge to a central hole in such a way that it forms a pie segment and is about 4 mm on its outside edge, 1 mm on its inside edge. The pieces form a pattern of eight coloured segments that repeats five times over the surface of the wheel.

The seven metal wheels each contain cut out patters intended to mask a portion of the coloured wheel beneath it. Six of these are anodized black and have an integrated pulley soldered to the centre of its bottom surface. The seventh is of uncoated brass and appears to have been locally made given the marks scribed on its surface. It does not have a pulley. The black wheels are 8.8 cm in outside diameter. The brass wheel is 10 cm in outside diameter.

The square wooden spacers are used to separate and secure the metal wheels when stored in a compartment in the wooden case. Each has a hole in its centre to accommodate the pulley of the metal wheels.

The loops of cord are meant to connect the pulleys on either side to each other in such a way that by turning the concentric pulleys on the right side using the attached handle, the wheels on the left are set spinning.

Accession Number: 2015.psy.160

Alternative Name:

Color blending apparatus after Kirschmann

Primary Materials: Steel, Wood, Glass


The worn maker’s label screwed to the instrument’s face reads “E. Zimmermann; Leipzig; Emilienstrasse 21”

Dimensions (cm):

Height = 6.8, Width = 17.8, Length = 40.5.


This instrument was intended “for demonstrating the compositions of white light, the complementary colors of the laws of color mixtures, as well as some particularly intriguing phenomenon of continuous color change.” [Zimmermann 1903, 4-5]

Note: This instrument is not the same as the instrument described in the catalogue entry cited above, though they are similar.

The two concentric pulleys rotated a coloured wheel, and a metal disc anchored above it at nearly the same rate. Parts of the transparent coloured disc were visible through cutouts in the metal mask. Because both were rotating rapidly, the component colours visible on the wheel and the black metal disk combined to produce a homogeneous blend of colour. Because the disk and the mask rotated at different rates, the portion of the coloured disk visible through the cutout in the metal disc changed with time. The effect was a shifting blend of colour. Different metal discs featuring cut-outs of various shapes were used to demonstrate different phenomena.


Good: With the exception of the broken glass wheel, the instrument is in good condition.

Associated Instruments:

Manufacturer: E. Zimmermann

Date of Manufacture: c. 1900 – 1910


This instrument was most likely supplied to the University of Toronto psychological laboratory by the E. Zimmermann workshop during the tenure of Professor August Kirschmann between 1893 and 1908.

Additional Information and References:

1) E. Zimmermann, <i><a href=”″>Preis-Liste ├╝ber psychologische und physiologische Apparate. XVIII.</a></i>, 1903. Provided by the Virtual Laboratory of the Max Planck Institute and Dr. Rand Evans.

Historical Notes: