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Glass tiles are pieces of glass
cut shaped to a variety of sizes.
Their surface is more easily made water tight and does not harbor mildew
or mold. They can be handmade or factory
manufactured. Glass reflects light
and can be very bright and intense in color. This gives a designer or
homeowner an opportunity to use color in a very modern way that ceramics
don't convey.Glass tiles are cleanable with water or glass cleaners. Glass tile is a great addition for bathrooms and kitchens and
areas where a non-allergenic surface is important.
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There are a variety of ways to
make glass tiles but four are predominant---smalti, fused, slumped and
cast. Color is added to the top or bottom for a
translucent but color-tinted appearance.Smalti tiles are usually small in size and made from a paste of
silica, sodium or potassium carbonate, metals for stabilizing and oxides
for color. The mixture is rolled out flat, fired and then hand cut.
Fused tiles, largely a factory product, are flat, clear glass that is
cut into tiles and then fired. Slumped glass tile is a curved
shape achieved by melting plate glass into a relief-type mold and
firing it at a low temperature. When the glass cools its curved shape
takes form. The glass is then heated and the
pieces meld together to form a tile.Cast tiles are made by filling a mold with pieces of glass,
which allows for some artistic flare as the choice of colors can be
mixed to create a multi layered look.
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Making recycled glass
tiles uses less energy and the tiles can be made from old windshields,
bottles and scrap glass.New technologies are allowing
for glass tiles to be made of recycled glass. Heat transfer dyes are added in some instances
to the back of a sheet of glass tiles to re-create photographs and art
in a tile format. Tiles created on a
smaller scale can be formed and shaped to create a mosaic tile as well
as more traditional shapes. Handmade tiles are also quite popular and generated by
a variety of smaller manufacturers worldwide.
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Glass is rigid where ceramics
are less so and therefore glass breaks more easily.Installing glass tiles works a
little differently than installing ceramic tiles. This is due to the
nature of the glass versus clay materials. The installer must
know how to drill through glass to accommodate fixtures and electrical
outlets. Tiles can be produced singly or in sheets, like ceramic tiles,
which allow for a faster installation.
Ways of Making Glass Tiles
Production methods, combined with color, size and shape,
determine a tile's look and feel. For people buying for a surface
application, creating a mosaic, or generally curious about how things
are made, the main production methods are outlined below.
Below, we display slides made with different production methods, followed by some notes on each type of tile.
There are four main types of glass tile: smalti, fused, sintered,
and cast. In addition, there are two prominent glass surface treatments
for these tiles: slumping and etching.
Smalti Tile
Smalti tiles are typically colorful, textured, small format tiles – good building blocks for artistic mosaics.
“Smalti” is an Italian word, and refers to a glass paste or glaze
made up of silica melted with sodium or potassium carbonate. Metals are
added as stabilizing agents, as well as metal oxides ( for color). The
paste is fired at high temperatures, then rolled out into a pancake-like
slab that can be up to 6 inches thick. Once cooled, the slab is
traditionally hand-cut into small rectangular pieces of tile.
Fused Tile
In the fused manufacturing
method, flat glass (usually float glass, such as glass used on car
windshields) is cut into tiles shapes and then fired in a furnace. Fused glass tiles are often translucent
tiles, with a layer of opaque color visible through the tile.
As
glass is clear, it will show the tile underpay unless treated with
color, so this method usually involves the addition of color – by adding
it on top or under the glass.
Fused tiles
can come in virtually any size – from mosaics to large format.
Fused tiles are often treated with an etching or other coating,
for aethetic reasons, or to increase resistance to abrasion.
Sintered Tile
These tiles are often sold in
arrays of 1" × 1" squares, but can come in sizes up to 3" × 3".
Sintered glass tile is made by pressing glass powder into dies and
then heated until the particles fuse.
In this method, color is either added into the powder or added
topically after cooling. With their milky, scratch- resistant finish,
sintered tiles are known for their versatility.
Unlike smalti tiles, sintered tiles tend to
have a uniform look.
Cast Tile
Cast tile is made by inserting chunks of glass into a mold. The mold is
heated until the pieces melt into each other and become a coherent mass. Most recycled glass tile products are made
using this method.
The result is a layered look.
Terrazzo
glass tile is a cast method that combines an concrete amalgam with glass.
Slumped Tile
Slumped glass has been curved into a convex or concave shape during firing. On cooling, the glass assumes a distinctive curved or contoured shape.
Slumping is usually achieved by melting plate glass into relief
molds at relatively low firing temperatures.
Etched Glass Tile
Etched glass is a proccess of applying a thin, translucent layer on the surface of a tile. This
layer can be achieved through one of three methods:
By applying an additional, cloudy glass surface to the top of the tile.
Abrasion. Devices can include sandblasters or laser cutters.
By applying an acid etch, such as hydroflouric acid, to the surface.
Making tiles from recycled glass
Typical sources of glass for
recycled glass tile are
bottles, jars or window glass.
To make glass from recycled glass sources, the raw materials must be
free of contaminants (paper, dirt, wrappers, etc.) and must be of
uniform source and color.
Different types of glass have different composition and color;
waste glass should be carefully sorted before use. Different glass
sources have different coefficients of expansion. As a result, the glass
will not cool as a uniform mass. Different manufacturing techniques give rise to different results.The negative results during cooling
can range from cracking to explosion.
There are three common methods of making tiles from recycled glass:
Small mosaic tiles are usually made from glass that is brought to a molten state along with glass color, poured over an iron table and
pressed with a form (cookie cutter) to create the small mosaics.
The glass and color mixture is heated to a high temperature
until it achieves a molten state. Once cooled, the pieces are separated
and the tiles can be assembled into sheets that are easy to install.
This technique involves small batch sizes and labor-intensive process of tile sheet assembly.
This technique is well understood and is relatively easy to set up. The
final product consists of small mosaic tiles with some color variation.
This variation is not critical, and may even be desirable. One
ecological advantage of this technique is that the broken tiles and
production waste are kept to a minimum because of the small module of
the tile. However, one disadvantage is the high heat required to heat
the tile - approximately 1400 degrees C.
Large glass tiles (50mm x 50mm and larger) can be
manufactured using the same technique as above, with one added step.
Larger tile modules create more production waste, and require more
color control and quality control.
The glass must be annealed in an annealing oven (kept at 500 C over
several hours) to remove the stress created during the cooling process.
Glass tiles can also be made from cullet (glass that
has been crushed and sorted into uniform particles) and placed in
ceramic molds. The advantages include
lower firing temperatures and a faster production cycle. The
disadvantages are - the colors are dictatedby the color of glass cullet
available from the recycling stream, i.e. green, brown or clear bottle
glass.This technique involves heating the glass to relatively
low temperatures (800 C) followed by annealing.
About Fused Glass Tiles
The higher the temperature, the greater the physical change in the
glass.
Fused glass tiles are made from intact pieces of glass that are kiln
fired at high heat – temperatures ranging from 1100°F to 1500°F.
Most contemporary fusing methods involve stacking – layering thin
sheets of glass. Often different colored pieces are stacked to create
visually interesting patterns or simple images.
At the lower end of the firing scale, the glass will simply slump –
rounding at the edges. The middle temperature range (around 1250°F)
creates an effect called ‘tack fusing’, layers of glass that are
sandwiched together will marry together, but each piece retains its
individual character. Full fusing, at temperatures of 1350 to 1450°F,
results in glass sheets flowing together, creating an radically changed
look.
A popular method of fusing involves marries glass to a colored
(usually white) background. The color on the back helps reflect light
back through the tile, which can give reflected light and the illusion
of added space to a room.
Because these tile are derived from sheets of glass, and not glass
powders or shards, there is almost no limit to the sizing. Manufacturers
and artisans sometimes used most industrial recycled glass, or spoiled
sheets of glass to make this type of tile. However, as different sheets
of glass have different pigments and chemical composition, it is
impossible to standardize color using; recycled fused glass tile is
usually reserved for artisan tiles or ‘rustic’ sheets.
High heat leaves the surface glossy, but this is sometimes
modified using etched techniques.Glass is then
annealed – cooled and soaked over specific intervals and temperature
ranges.
Fusing involves a series of ‘ramps’ – rapid heating cycles, and
‘soaks’ – where the temperature is held at a constant level. The longer
the kiln is held at the maximum temperature the more thoroughly will the
stack fuse. Sustained high heats can devitrify glass, so once the
desired fuse is attained, the kiln temperature is lowered.
Terrazzo Glass Tiles
Glass terrazo is now available for any number of institutional
settings, and is also used as a residential floor surface.
Modern glass tile manufacturers have built on the traditional
terrazzo techniques to develop looks that make full use of glass' unique
ability to deepen color and reflect ligh
A decorative technique was developed, where wooden strips were laid
into the amalgam, and later removed, leaving channels for colorful
marble dust, and later, 3/4 inch colorful marble cubes, known as Mosaic
Tessarae.
Developed in the 15th Century, marble terrazzo made use of scraps of
marble by traditionally bonding them with clay, and sealing them with
goat's milk. The resulting flooring was then ground and polished smooth,
then finished with wax, linseed oil, and turpentine. Terrazzo flooring
was often used on outdoor terraces ( ‘terrassa’ in Italian), where this
technique got its name.
In the modern era, clay has been replaced by Portland cement. Coupled with
the development of industrial grinders, this flooring technique has become
more cost effective and commonplace. More recently, there has been new interest
in glass surfaces, and the development of modern epoxies, polyesters, latex
and acrylics have made it possible for manufacturers to introduce glass
into new surfaces. Now terrazzo is available using recycled glass, instead
of marble.
Smalti Tiles
Smalti tiles were originally developed to complement natural
marble and granite tile colors. Newer oxides have enabled smalti tile
makers to venture into nontraditional looks as well. As a glass tile,
Smalti tiles are also weather- and stain-resistant, and are relatively
easy to cut.
Smalti tiles are typically colorful, textured, small format tiles.
“Smalti” comes from Italian, and refers to a paste or glaze made
up of silica melted with sodium or potassium carbonate. Metals are added
as stabilizing agents, as well as metal oxides (for color). The paste
is fired at high temperatures, then rolled out into a pancake-like slab
that can be up to 6 inches thick. Once cooled, the slab is traditionally
hand-cut into small rectangular pieces of tile.
Artisans typically turn the resulting tiles (also called tessarae)
on their sides, as this exposes swirls or layers of colorful textures.
The modern “smalto” method has the smelted paste cast in a
capsule, rather than rolled out and cut. The capsules, which enable the
mass production identically-sized tiles usually produce tiles in the
3⁄4" × 3⁄4;" × 1⁄8" format (i.e. 20mm × 20mm × 3mm).
All these features have made the popularity of this type of
tile endure among modern mosaic artists and hobbyists as well.
Popular Variants
Translucent Smalti are lightly colored smalti
tiles that look like stained glass, except that the colors are uniform
throughout the smalti tile. Translucent smalti have glistening surfaces,
with the visual depth of translucent glass.
Gold Smalti are made by applying a gold leaf,
followed by a thin layer of blown glass, against a Smalti slab, and then
heating to sandwich the layers together. The tile is subsequently used
face up, as in Byzantine glass.
Gold leaf has been traditionally associated with transcendental
beauty and greatness; these tiles were often applied to religious
decorations and murals.
The gold leaf is typically either white gold (which looks silver when applied), 24K yellow gold, or platinum.
Byzantine Glass is made from thinner slabs of
glass, usually about 1⁄2 the thickness of a typical smalti slab. The
slab is cut roughly to squares, most pieces being somewhat irregular in
shape, about 10mm (3⁄8 inch) in size.
As it cools, the surface of a smalti slab undergoes more
unpredictable color changes than on the interior of the slab. This, for
better or worse, makes for more variations among Byzantine Glass pieces
than in other Smalti tiles.
Thickness also varies, 4-6mm
(3⁄16-1⁄4"). Note that the surface of the slab, not the side, is used as
the face of the tile.
Metallic Smalti describes when a swirl of a
copper-bearing mineral is added into the molten glass before it is
pressed. On drying the metal appears as a copper-colored streak running
through the body of the glass.
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