What Goes in a Kaleidoscope Object Cell: Brewster's Rules for Objects, Colour and Motion

5 days ago

7 min read

The mirrors of a kaleidoscope repeat whatever sits at their far end. They add symmetry and nothing else. Shape, colour and the way the pattern changes all come from the kaleidoscope object cell: the container holding the objects in front of the mirror system.

Chapter VIII of Brewster's book, "The Kaleidoscope: Its History, Theory, and Construction", is titled "On the selection of objects for the kaleidoscope, and on the mode of constructing the object-box". This article summarises that chapter, adds what Chapters III and VII say about motion, and then lists the object formats in use today. The text consulted is the second edition (London, John Murray, 1858). Brewster's term is "object-box"; the current term is object cell.

Why Brewster thought selection matters

Chapter VIII opens with a qualification. The instrument forms a symmetrical figure from any shapeless object, but some shapes and colours give far better results than others. Brewster states that its capability cannot be judged "unless the objects are judiciously selected".

His first rule links object size to mirror angle. When the inclination of the reflectors is large, the sector seen directly is wide, and the fragments should be larger. Small fragments in front of a wide aperture give a spotted pattern, because the outline of a fragment does not reach the mirror and so does not join its own inverted image. For the mirror geometry behind this, see how a kaleidoscope works.

Shape: which outlines work

Preferred: curved forms - circles, ellipses, looped curves like the figure 8, curves like the figure 3 and the letter S, and spirals.
Also usable: squares, rectangles and triangles.
How to make them: spun and twisted glass formed into those shapes.
Thickness: spun glass and coloured plates should be as thin as possible.

Material and transparency: what to include and what to reject

For a cell viewed against the light, Chapter VIII lists:

Spun and twisted glass in the shapes above.
Pieces of flat coloured glass.
Blue vitriol, native sulphur and yellow orpiment.
Coloured fluids, enclosed and moving inside small glass vessels.
Iron or brass wire, twisted into forms and hammered broader and flatter in places, mixed with a few small fragments of coloured glass.
Lace, and strings of beads on wire or thread.

He also lists what to keep out:

Fragments of opaque glass.
Dark colours that transmit little light.
Glass with cut and polished faces, which he calls "ill fitted for objects".

Opaque objects have a separate arrangement. Chapter VII describes a flat box with a bottom of mirror-glass, lit from the front. For that box Chapter VIII recommends adding opaquely coloured glass, brass wire, coloured foils and grains of spelter to the transparent fragments. The same object is therefore rejected in one cell and recommended in the other, depending on the direction of the light. See how to light, view and photograph a kaleidoscope.

Construction of the object-box

Gap between the two glass plates: as small as possible, not exceeding one-eighth of an inch (about 3.2 mm).
Outer plate: ground on its external surface. Its function is to stop outside lines, such as window bars or the outline of a flame, from entering the picture.
Inner plate, next to the reflectors: only thick enough not to break.
Brass rings holding the plates: the interior diameter must be large enough that no part of the rim comes opposite the angular point of the reflectors while the cell rotates. Otherwise the rim blocks the centre of the pattern.

What to check: look at the centre of the pattern while turning the cell. If a dark edge enters the centre at any point of the rotation, the rim of the cell overlaps the mirror junction.

How much freedom the objects need

The fill level is stated as a fraction: the box should be "nearly two-thirds filled" with the mixture of regular and irregular objects. Brewster gives two corrections:

Objects fall with difficulty: turn the screw of the box back two or three turns to widen the gap.
Objects fall too easily and pile up behind one another: reduce the gap by placing an additional glass inside the box, against the ground glass.

Loose, fixed and vibrating objects

Brewster describes several cells for one instrument, each with a different function.

Loose objects. The picture changes continuously. It cannot be held, and it cannot be shown to a second person.
Fixed objects. Pieces of spun and coloured glass are cemented with a transparent cement to the inner side of the glass. After a complete rotation of the cell the same patterns recur, so a pattern can be recalled and shown to others.
Vibrating object-plate. A plate of smaller diameter than the cell, containing loose objects. It vibrates on its lower edge when the horizontal tube is tapped.
Colourless box. Fragments of colourless glass, or an irregular surface of transparent varnish or hardened Canada balsam. Used alone it gives colourless figures. Placed between a coloured box and the mirrors, it softens the outlines of the coloured pieces by refraction.

Colour: fewer tints, chosen in pairs

On colour, Brewster's position is restrictive. He writes that the eye is satisfied by the symmetry of the outline and not by the number of tints.

His remedy is to admit only colours that harmonise, by which he means complementary pairs: two colours that form white when mixed. The chapter includes a table of such pairs. Two examples from the text are red with bluish green, and indigo with orange-yellow.

He then specifies a cell built on one pair. Four or five regular figures are made in indigo glass and the same number in orange-yellow glass, some drawn thinner to give a lighter tint. Colourless spun glass and flat fragments of both colours are added.

The last step goes further. Objects of a single colour in several shades, mixed with colourless spun glass, are in his words "perhaps even superior to the combination of two harmonic colours".

Motion: how the objects cross the aperture

Brewster discusses motion in Chapters III and VII. The points that concern the object cell:

Rotation with loose objects (Chapter VII). The fragments descend by gravity and cross the aperture in concentric circles. Brewster treats this as a defect: the changes are unlimited in number, but they always occur in a similar manner.
Sliding plates (Chapter VII). His correction is a rectangular object-plate moved through a groove in the cell, in the manner of a lantern slide. Fragments can then cross the aperture in any direction, and rotation and straight-line motion can be combined.
Fixed objects with rotating mirrors (Chapters III and VII). The picture divides into two sets of sectors. Sectors formed by an even number of reflections stay at rest; those formed by an odd number move.

Object formats today

This section is separate from Brewster's text and describes current formats in general terms only.

Dry cell. A closed cell holding loose objects and no liquid. The objects fall under gravity when the cell is turned. This is the arrangement of Brewster's object-box with loose objects.
Oil-filled cell. A sealed cell in which a liquid holds the objects in suspension. The Brewster Kaleidoscope Society names mineral oil, glycerin and silicone as the liquids in use. The objects drift, so the pattern continues to change after the hand stops. Brewster's chapter lists fluids sealed in small glass vessels as objects, not a cell filled with liquid. See oil-filled vs dry cell.
Object wheel. A disc mounted on an axle in front of the mirror system and turned by hand. The objects are fixed in the disc, so a given wheel position returns the same pattern. In function this is close to Brewster's fixed-object plate.

The formats are compared in types of kaleidoscopes, and the terms are defined in the kaleidoscope glossary.

Checklist: reading an object cell by Brewster's criteria

Are the outlines mostly curved, with some straight-sided pieces?
Do the fragments reach the mirror edges, or is the pattern spotted?
In a back-lit cell, do all the pieces transmit light?
Is the centre of the pattern clear through a full rotation?
Do loose objects fall freely without stacking behind one another?
How many colours are present, and do they form complementary pairs?

FAQ

What is a kaleidoscope object cell?

It is the container at the far end of the mirror system that holds the objects the mirrors repeat. Brewster calls it the object-box in Chapter VIII of his book and specifies two glass plates no more than one-eighth of an inch apart, the outer one ground to block outside lines from the picture.

What objects did Brewster recommend for a kaleidoscope?

Chapter VIII lists spun and twisted glass formed into circles, ellipses, figure-8 loops, S-curves and spirals, with flat coloured glass, blue vitriol, native sulphur, yellow orpiment and coloured fluids sealed in small glass vessels. He also mentions twisted and hammered iron or brass wire, lace and strings of beads.

Which objects did Brewster reject?

For a transparent cell he rejects fragments of opaque glass and dark colours that transmit little light, and he states that glass with cut and polished faces is "ill fitted for objects". Opaque pieces are assigned to a different arrangement: a flat box with a mirror-glass bottom, lit from the front.

How full should an object cell be?

Brewster specifies a box "nearly two-thirds filled" with a mixture of regular and irregular objects. If the objects fall with difficulty, the gap between the glass plates is widened by two or three turns of the screw. If they pile up behind one another, an additional glass is inserted to narrow it.

How many colours should an object cell contain?

Brewster argues for few. He recommends complementary pairs, such as indigo with orange-yellow or red with bluish green, and describes a cell built from one pair plus colourless spun glass. He adds that objects of a single colour in several shades may give a result superior to two harmonic colours.

What is the difference between loose and fixed objects?

Loose objects fall when the cell turns, so the picture changes continuously and cannot be repeated. Fixed objects are cemented to the glass of the plate; Brewster notes that after one complete rotation of the cell the same patterns recur, so a pattern can be recalled and shown to another person.

About Studio Yabaye

Studio Yabaye builds kaleidoscopes and teleidoscopes with front-surface mirror systems in a brass tube, cut, fitted and hand-finished in the studio. Each object wheel is poured and composed by hand, so no two pieces are alike. The studio is based in Israel and ships worldwide. See also what you see inside a handmade brass kaleidoscope. The current range is at all products, and questions can be sent through the contact page.