Seed Bead History and Production of TOHO Beads

What are beads?

Basically, the word bead means “a small ball with a hole”, but in fact there are a variety of shapes, sizes, and materials. In the modern age, the most common material is glass.


The origin of beads

Natural materials used for beads have included, among others, wood, shell, fruit, seeds, stone, animal teeth, fish vertebrae, ivory, coral, and ostrich eggshell. In ages when the sun and moon were recered as god, the wearing of round beads, with shapes echoing those of the sun and moon, seems to have held great importance for ancient people.

The origin of beads fashioned from natural materials is very old, dating to the dawn of humanity. Beads made from small shells have been found strata dated over 75,000 years of age.


Beads before glass

Around the 16th century BC, Mesopotamian craftsmen began making glass balls. Not long afterward, in the 15th century BC, such glass balls also began to be made in Egypt. These early balls were very simple. Over time, such techniques as lampworking gave rise to ever more beautiful and complex designs.


Cylinder beads

During the last decade, a new shape of Japanese seed bead, the cylinder bead, has become increasingly popular. Unlike the more rounded donut-shaped rocaille seed beads, cylinder beads are extremely uniform in shape and size and have large holes for their size. Their flattened ends mean that bead work created with cylinder beads has a flat, smooth texture. Rows and columns in weaving line up more uniformly, so detailed pattern work comes out more accurate and even. These beads are more expensive than round seed beads, although the reduced weight of the thin walled cylinder beads results in more beads per gram.

There are three versions of cylinder beads:

– Treasure by TOHO
– Aiko by TOHO
– Delica by Miyuki

The holes on Japanese TOHO cylinder beads are very large.  Consequently, they can accommodate many thread passes.

TOHO cylinder beads work well with most beading stitches, but in particular work well with square stitch, flat peyote stitch, and ladder stitch.  In addition, cylinder beads can be used to make beaded ropes. They can also be used in bead crochet.

TOHO cylinder beads are the preferred seed bead for people who do loom beading because it results in an even beadwork cloth. The large variety of bead colors means that pictures and artwork can be precisely rendered using Japanese cylinder beads.


Production Method of Glass Beads

There are 4 main methods of producing glass beads.

1. Lampwork Glass Beads (Mandrel wound beads)

In this method, molten glass is wound around a metal mandrel. This technique may have begun in ancient Mesopotamia or Egypt.

2. Drawing Glass Beads

By this method, molten glass is drawn to form a straw-like tube, then cut into small pieces that are reheated to make the cut surface rounded. Today, small round beads are made using this method.

3. Molded Glass Beads

In this method, heated glass canes are pressed between upper and lower wooden molds, then removed.

4. Blowing Glass Beads

In this method, beads are shaped by blowing air directly into molten glass.


Japanese Seed Beads

In Japan, seed beads were called Nanjin balls. They were imported from Germany around 1921, following by the beginning of Japanese manufacture. The industry was small, however, with only two to three factories including Aoki Wasaburo Factory in Tondenbayashi, Osaka and the Nakajima Glass Factory in Sakai, Osaka.

Today, Japanese seed beads are regarded as the best in the world. One of the 2 major Japanese bead manufacturers, TOHO Co. Ltd. Began manufacturing glass beads as “TOHO Glass Beads Factory” in Hiroshima City under the founder Ichiji Yamanaka in 1951, soon after the war. TOHO is continuously making forward strides, putting their technology in competition against the other major manufacturer (Miyuki) in Fukuyama City, Hiroshima.


How to Make TOHO Seed Beads

1. Glass Cane Making

1-1. Blending Materials

The glass used in making seed beads is called “ soda-lime glass”. This is the most common kind of glass, also used for window panes and glass bottles.

The main components of soda-lime glass are silica sand (SiO2), soda ash (Na2CO3) and lime stone (CACO3). Soda ash contains sodium (Na) which helps silica sand melts easily. The calcium (Ca) in lime stone prevent glass from dissolving in water.

Unlike making windowpanes or bottles, making seed beads requires various colors of glass. And to make clearer, purer colored glasses, you must use materials with few impurities. In particular contamination by iron must be avoided, since it can result in blue-green glass.

To color glass, various coloring agents are used. Table 1 shows the main coloring materials.

Scaling the powdered coloring materials and the main material  to the designated composition (constituents in their proper ratio) and mixing them is called “blending”.

Many kinds of seed beads show the same color, but differ in size and shape. Even if the color of beads looks the same, the blending composition of each is different. When shape and size are different, the bead’s thickness varies. Because of this, the brightness of the glass’s color must be adjusted by blending materials so that the beads’ colors appear identical even if the size and shape are different. Even if the glass itself is a fixed color, thicker glass will appear darker, while thinner glass will show a lighter hue.

3 types of glasses of different transparency are used for seed beads. Transparent glass is called “Transparent”, the semi-transparent glass is called “Ceylon”, and the non-transparent glass is called “Opaque”.

By making glass opaque, glass transparency can be adjusted. Usually, fluoride (a compound of fluorine and other atoms) is used as an opalizer. Opalization creates small crystals called cooloids (a state in which super fine grains, larger than molecules or ions, are dispersed in media such as liquid, gas, or solid substances) in the glass. The colloids scatter light, making the glass look opaque. The more and larger the colloids generated, the more opaque the glass becomes.

Trivia : Even when coloring materials are blended with the main material in the same way and at the same ratio, it doesn’t always create a uniform color. Experienced craftsmen monitor subtle changes in the glass’s condition and adjust the color. It’s especially difficult to maintain uniformity for colors in the red portion of the spectrum.


1-2. Melting

After heating the raw glass material, blended from main material, coloring materials and opalizers, to 1300 degree (Celcius) for about 20 hours, a candy-like soft glass will be made. This process is called “Melting”. The melted glass is called “molten glass”.

Pieces of waste glass of the same type (cullet), left over from each process, are added to the blended raw materials in a predetermined ratio during melting. Cullet is waste glass from each process. Recycling cullet in this way helps create more uniform melting.

2 kinds of furnaces are used to melt glass. One is the “Pot Furnace” used  to produce small batches of glass. So called “Tank Furnace” is used for larger scale production.

Trivia 1 : There are several kinds of pots. Currently, the one used most often to make seed beads is a jujube-shaped pot called a “Class Pot”. For comparison, the “Side Opening Crucible” is the most used pot for melting glass generally. In Japan, the Side Opening Crucible is called a “Cat Pot” because the shape resembles a sitting cat.

Trivia 2 : The pots are made of refractory (heat resistant) material, and must be heated gradually over a period of up to 3 days before being used. If the pot is heated too rapidly, it will crack. This process is called “Pre-Burning the Pot”.

Tank Furnace

Add glass raw materials to a large tank built from firebricks, and heat the material directly by electrifying a pair of electrodes. This tank is connected to the subsequent process site where glass canes are shaped. These furnaces can process a larger quantity of glass than pot furnaces. Once this furnace is heated, the same type of glass will be mass produced for several months or more. After raw materials are placed in the furnace, it takes about 3 days until they’re ready. At the end of the process, all molten glass is drained from the furnace, the brick is broken down, and a new furnace is constructed.

Trivia 1 : Glass doesn’t conduct electricity at normal temperatures. Molten glass, however, will conduct electricity. The tank furnace takes advantage of this property. At the beginning, though, glass cullet must be melted using another heat source (burner or equivalent).

Trivia 2 : The sensor of melting glass (such as sensor for detecting the level of molten glass) is made of platinum, which is resistant to high temperatures and corrosion. For the same reason, pots for making optical glass are made from platinum because optical glass must be as free from impurities as possible.


1-3. Drawing

Molten glass is shaped into a long thin tube with a hole in the center, called a cane.

When a pot furnace is used, the molten glass is scooped out and placed on a metal plate. Then it is folded several times until it cools to a temperature suitable for drawing the glass and is then places into a cane shaping pot.


When a tank furnace is used, the furnace and cane shaping pot are connected, allowing the molten glass to flow directly into the shaping pot. When the glass which has been transferred to the cane shaping pot cools down to 800-900 degrees (celcius), it is drawn out by a pulling machine, with compressed air blown into the cane’s center.

At the bottom of the cane shaping pot, there is a hole called the orifice. The shape of the orifice determines the outer shape of the cane. Orifices have many shapes, including circles, triangles, squares, hexagons.

When molten glass exits the orifice, air blown with a tube called the plunger forms a hole in the center of the cane. Most seed beads have round holes. However, for seed beads with a square hole, a square plunger is used.

The size of the hole can be adjusted by the air blown through the plunger. To check the size, randomly choose one cane and inserted a rod with the specified diameter into the cane. The hole’s position is also adjusted to the cane’s center by appropriate positioning of the plunger and orifice. However, for comma-shaped beads the hole is deliberately set off-center.

The molten glass, which exits the cane shaping pot, is pulled about 30 meters with a cane shaping machine. While it is pulled, the molten glass gradually cools, becoming harder and thinner. Depending on the speed with which the cane shaping machine draws the glass, the outer diameter of the cane can be adjusted. If the molten glass is pulled quickly, it becomes thinner. When pulled slowly, it becomes thicker.

The long tube pulled by the cane-shaping machine is cut into lengths of approximately 60 cm. Cut canes are placed in a wooden box and carried to the next process.


1-4. Filtering Canes

Raw canes are filtered through an inspection board with size-specified holes to check their diameter. The passed canes are bundled and tied at bottom and top. The canes which don’t meet the specified size are returned to the blending process and melted again as cullet.


2. First Processing (Cutting – Raw Beads Processing)

2-1. Cutting

Canes are cut with a special cutting machine, a disk blade rotates horizontally at high speed. When canes are inserted vertically into the machine, they’re cut from the bottom. The length of the cut cane is determined by the desired size of the finished beads. Therefore it’s important to cut the cane horizontally and at uniform lengths.

Trivia : Canes which have already been broken or shortened can have an adverse effect on cutting process. To prevent this, canes are sorted by hand prior to cutting and aligned with canes o f a similar length. This step is called length alignment.


2-2. Reheating

Cut beads and charcoal sand are mixed and heated in a rotating furnace at 700-750 degrees (Celcius). The cut edge meltes and tube shaped beads take on a round shape.

By mixing charcoal sand into beads, the softened beads will not stick together and the holes will not be damaged. This is called the Carbon Method.

Trivia : The surface of reheated beads is coated with charcoal sand. Therefore, the actual color of the glass is invisible. Careful control of both the quality of charcoal sand and temperature adjustment are the keys to making beautifully formed beads.


2-3. Rinsing

To remove the charcoal sand from the surface of the beads, fluorine, a chemical agent which can dissolve glass, is added during rinsing. This is also called First Rinsing. A large, tilted tub like a laundry machine tub rotates to rinse the beads. When the beads are completely rinsed, they are vacuumed through a hose by a vacuum pump and transferred to a centrifuge machine which acts as a dehydrator. Water is removed by dehydrating the beads for about 30 seconds.

Trivia : One of the reasons Hiroshima is home to many bead factories is because of the area’s clean water. By using clear water for rinsing, more beautiful beads can be made.


2-4. Finishing

The surfaces of the rinsed beads are lightly frosted. To make them shiny and beautiful, the beads’ surfaces are melted by heating them again in an electric furnace at 650-700 degrees (Celcius), which is a bit higher than the temperature at which glass softens. If the beads’ surfaces are uncoated, the beads are finished after this step.

Trivia : Depending on the kind of bead (color, shape, size), it shines differently. The temperature of the furnace is controlled carefully, but checking the quality of the beads’ shine requires human eyes.


2-5. Frosting

To remove the glaze of the beads completely, they pass through a frosting process. There are two methods. One is placing beads and an abrasive compound into a frosting machine to physically abrade the surface for pear-skin finish. The other method is chemical abrasion.


2-6. Filtering Beads

Finished beads are filtered according to their outer diameters. First, the beads pass through a screen with small holes to drop beads that are too small. Next, beads pass through a screen with specified hole sizes so the only beads of that size drop through the holes, eliminating oversized beads. Thus only beads of the specified size are sent to the next process. Other beads are sent back to the blending process and melted again as cullet.


3. Bead’s Surface Treatment

From the 3 kinds of glass, Transparent, Ceylon (semi-transparent) and Opaque, canes of various colors are made and formed into beads. In the second round of processing, further colors are created by applying different surface treatments including plating, inside color, surface coloring, metallic, luster, rainbow and glazing. Sometimes only one of these treatments is applied to the beads. But when several treatments are applied, various colors and surface textures can be created. For internal color, the whole bead is treated, and then abraded to remove the surface treatment, so the the color and treatment shows only inside the holes.


3-1. Plating

Plating covers the bead’s surface with a thin metal film. There are two main methods for plating beads, “Electroless Plating” and “Electroplating”.

In “Electroless Plating”, the metal is precipitated onto the surface by the chemical reaction of metal ions and a reductant in the plating solution. Even non-metal materials can be plated evenly. Place plating solution and beads in a container and mix them to plate the beads.

“Electroplating” is a method in which the plating metal is precipitated using electricity. The material to be plated must be electro-conductive. Glass doesn’t conduct electricity. Therefore glass must first be derivatized by electroless plating. Then elecroplating is applied to the electroless-plated beads. To plate the beads, they are placed in a barrel filled with plating solution, and then electrified.

The plating metals for decorative purposes are silver, nickel, tin, gold, copper, rhodium, palladium, etc. Generally, for gold electroless nickel plating is applied as a base coat and then electroplating is applied over that. Gold is a soft metal, so in some cases, a tiny amount of cobalt is added to gold. Also, to alter the color of gold, sometimes a small amount of copper (for pink gold) or silver (for lemon gold yellow) is added.

Some beads are plated over their whole surface. Others are plated only inside their holes. To plate inside the holes, first the entire bead is plated and then the surface plating is abraded. Beads with silver plating only in their holes are called “Silver Lined”.

Trivia : After silver and copper plating, a protective coating is applied for finishing. However if these beads come into contact with chlorine bleach or are oxidized over time, they may tarnish. You should take care when handling these beads. Plating with nickel, tin, rhodium and palladium may be worn away by friction. Be careful not to rub them.


3-2. Metallic/Luster/Rainbow

By applying metal-oxide vapor deposition to glass, bright glass and rainbow colors can be created. Vapor deposition is a method of creating thin film through chemical reaction including oxidation or resolution onto a highly-heated surface by vaporized metallic compounds. For beads, oxidized material of titanium or tin is vapor-deposited.

As the film grows thicker, the color changes to glossy white>brown>navy>green>purple. “Luster” (glossy white), “Metallic” (color created by thickening a film on a black opaque bead’s surface), “Rainbow” (glossy rainbow color, which shines in various colors, by making the film thickness uneven).

The principle of this color-forming treatment is an interference phenomenon of light like the iridescence on soap bubbles. Interference phenomena occur when two light-waves effect each other, sometimes being strengthened or sometimes weakened from time to time. With these beads, light is reflected or refracted both on and behind this thin film, causing a multipath reflection. That’s why the beads shine with a rainbow color.


3-3. Coloring

By mixing different types of dyes and pigments, coloring liquid for beads is made. Beads are put in a coarse textured bag and the bag is soaked in a bowl filled with dyes or pigments. Afterwards, the beads are dried in the bag, shaken so that the beads won’t stick together. This also works to evenly color the inside of beads’ holes, necessary for beads with internal color.

There are 2 types of coating. One is Surface Color, which colors the outside of the beads. The other is Inside Color, which colors only inside the holes. For Inside Color beads, first the entire bead is colored, and then polished to remove only the surface color of the beads. Seen through glass beads of various colors, internal color can appear to change. Combination with other coatings, such as luster or rainbow, expands the possible range of colors for beads.


Beads which have been silver-plated overall and then treated with surface coloring are called Galvanized beads.Dyed-Silver Lined beads are those beads whose holes are silver-plated before a surface color treatment is applied. Depending on the type of coating material to be applied inside the holes, the names of beads vary. Those with pearl-toned metallic coating in the holes are called Pearl beads. Beads with neon-like, vivid fluorescent coating in their holes are called Luminous Color beads.


3-4. Luster Coating

Apply gold luster or other luster coating material to the surface of bead, and then fire it on a belt conveyer. To prevent the coating material from entering the holes, TOHO’s professional craftsmen have developed their own techniques to judge the perfect timing for application of their own, originally developed coating material. Beads which begin as black before gold luster is applied to the surface are called Bronze beads.Transparent or opaque colored beads, after gold luster has been applied to their surfaces, are called Transparent/Opaque Gold Luster.

By applying gold luster followed by additional luster coatings, a variety of colors can be produced. For example, when gold luster is applied to the surface of black opaque beads and then additional luster coating is applied, the beads will be called Higher Metallic beads.


Trivia : Even when some gold luster is applied, finished beads will appear different according to their original type. For example, black opaque beads with gold luster coating look gold. White transparent beads with gold luster are translucent purple. White opaque beads with gold luster look pink.