| Keyword |
Explanation |
| A |
|
| Air side |
The side of float glass that was up, facing air
in the making of float glass. See also Tin
side |
| Alkali |
Sodium and potassium are alkali metals. In glass making sodium or
potassium carbonate is used as flux, to dissolve
silica. |
| Alumina |
Aluminum oxide. |
| Aluminum oxide |
A hard mineral used as an abrasive in sandblasting and grinding.
Usually found in powder or grain form or bonded to an abrasive wheel,
disk, pad, or bit. Chemical name is Al2O3. |
| Anhydrated |
see Calcinated |
| Annealing |
The process by which the stress in the glass is relieved and the
molecules in the glass are allowed to cool and arrange themselves into a
solid, stable form. Successful annealing is the key to creating
glasswork that will remain stable once it cools to room temperature. Click
here for a more detailed discussion of Annealing. |
| Annealing point |
A temperature in the annealing range with a specific viscosity of 10
to the power of 13 poises. (Poise is a measure of viscosity.) |
| Annealing temperature |
The specific temperature at which annealing occurs most quickly.
It's generally closer to the upper annealing point than to the strain
point. (Note that the annealing point,
a theoretical temperature that corresponds to a particular viscosity of
the glass, is not necessarily the same temperature as the annealing
temperature.) |
| Annealing range (or zone) |
A temperature zone where the molecules in the glass make their final
transition from liquid to solid. There are three critical
temperatures within this range: the upper
annealing point, the annealing
temperature, and the strain point. For
many common glasses, the size of the annealing range is is approximately
150F/83C, but the range can be as great as 200F/111C or as small as
100F/56C. |
| Archives |
The warm glass board archives all postings. These are kept in
one of two different databases. Posts from March 2000 to March
2003 are kept in the Old
Archives, which can be accessed using the "Old Archive"
button on the Bulletin
Board. Posts after March 2003 can be searched using the
"Search" button on the Bulletin
Board. The two archives are in different formats, but together
they contain extensive and valuable information and discussions on
kiln-forming. |
| Aventurine |
Translucent glass with sparkling inclusions of gold, copper or chromic
oxide. The name derives from the mineral aventurine, which is a quartz with mica particles. |
| Aussie Roll-Up |
See roll-up. |
| B |
|
| Bail |
Used in making jewelry: a loop or something that allows a pendant to
be hung on a chain. |
| Baffle |
A wall made of fiberboard, kiln bricks or other refractory material
that shadows off some of the direct radiation of nearby elements. The
purpose is to prevent overheating the edges of the glass, which can lead
to devitrification. A well
constructed baffle also improves evenivity. |
| Bat |
1. A slab of plaster or similar material
2. British term for Kiln shelf |
| Bat wash |
British term for Kiln wash. |
| Base |
1. A piece of sheet glass on top of which another piece is fused.
2. Chemistry: the opposite of acid. When working with
hydrofluoric acid, a proper base must be readily available to
neutralize. |
| BE |
short for Bullseye glass Click
here to visit Bullseye's website. |
| Bead |
1. From jewelry:
A stone, piece of glass, etc. that has a hole in it, so that it can be
strung on silk, wire, leather, etc.
2. Also using in fusing
to refer to a chad of glass used to prop up a top
layer of glass to allow air to escape.
|
| Bentonite |
A type of clay which has the capacity to absorb water, causing it to
swell when wet. Can be used as a suspension agent or mixed with sand for
sand casting. |
| Bevel |
A slanted edge ground into glass. A bevel shapes the edge of the glass
to form an angle that is not a right angle. |
| Bezel |
Jewelry: The metal that is used around a cabochon
to hold it in place. The bezel is bent slightly around the cabochon,
which is what holds the cabochon in place |
| Billet |
These are performed slabs of transparent glass which are often used
for casting into a mold. Size can vary by manufacturer, but they
tend to be around 5" x 10" x 3/4 " and weigh
approx. 3.5 pounds each. |
| Binder |
1. A medium used in glass painting to fix the color before firing.
2. An added ingredient in refractory materials like fiber boards, fiber
paper, etc. Usually burnt out before use by heating the material in the
kiln. |
| Bisque firing |
An initial firing of ceramic ware that hardens the item. In
ceramics, a bisque firing often takes place prior to glazing the piece
and refiring. |
| Bisque ware |
Fired, unglazed ceramic ware. Often used by glass
artists for slumping molds. |
| Blank |
A half fabricated annealed piece intended for further working. In
fusing a homogenous base plate is often called blank. |
| Blisters |
UK English: usually unintended bubbles under
the surface of the glass |
| Bloom |
A whitish discoloration on the tin side of
float glass. Often, these appear as stretch marks, with small gaps
between frosted areas. Bloom is sometimes mistaken for devitrification. |
| Borax |
Boron oxide in powder form. It is dissolved to water and used as an overspray.
Matures (melts into glass) at 741 C. Further reading: http://www.warmglass.com/making_your_own.htm#devitspray |
| Borosilicate |
A glass of very low COE used for laboratory glass
and cooking ware. Not so common in kiln working. It is extensively used
in lampworking. |
| Brilliant Cut Glass |
Glass decorated with wheel cut linear patterns. The cuts have a
prismatic effect that adds brilliance. |
| Bubbles |
Air trapped inside the glass. In UK also called Seeds. see Bulges |
| Bulges |
Air trapped under the glass which expands and distorts the
form. These are also called bubbles. |
| Bullseye |
A glass company that manufactures tested compatible glass for
kiln-forming. Click
here to visit Bullseye's website. |
| Burner |
A device to produce the flame for lampworking.
The fuel is mixed in the burner with air or oxygen to improve burning or
increase the temperature of the flame. |
| Burning Out |
1. Heating to evaporate
and drive off free and chemically bound
water from a mold.
2. Heating to melt out wax residues in the lost
wax casting process.
|
| C |
|
| Cab |
See cabochon |
| Cabochon |
A stone with a rounded surface, rather than with facets. Glass
cabochons are often used in making glass jewelry. |
| Calcinated |
Material where the water bound to crystal structure has been
removed. Also anhydride. |
| Calcium carbonate |
A white, insoluble mineral made from calcium, carbon, and
oxygen. Extremely abundant in nature in limestone, marble, chalk,
oyster shells, and related substances. Also known as
whiting. The chemical forumula is CaCO3. |
| Calcium oxide |
CaO, Lime |
| Cap |
To place a single continuous layer of glass (usually clear) on top of
a piece to be fused. Capping helps reduce the probability of devitrification. |
| Came |
A strip of lead with a H-section to joint
panels in traditional stained glass works. Sometimes spelled cane. |
| Cane |
A round, solid piece of glass that's approximately 4 to 10 mm
thick. Most often used in lampworking, rods are approximately the
size of a drinking straw or pencil. Also called a rod. |
| Casting |
in kiln casting the glass is treated in so high temperature that it
flows to the form of the mould, and the top surface levels out. Compare
to slumping where a glass sheet follows the mould form with both lower
and upper surface. See Frit Casting and Pot
casting |
| Catch |
Jewelry: a fastening device on a chain, so that the wearer can open it
and close around the neck or wrist. |
| Catcher |
Jewelry: the metal fixture behind a pin. |
| Cathedral Glass |
Colored translucent or transparent hand
or machine
rolled sheet glass with surface texture. |
| Cerium oxide |
A widely used polishing compound, most frequently used for final
polishing. |
| Chad |
A little blob or shard of glass. Put under the edge to initially
separate fusing pieces so that air can escape as the melting glass will
touch in the center first. |
| Chamotte |
European term for grog |
| Check |
Crack, usually from improper annealing. |
| China Clay |
see Kaolin |
| Cire Perdue |
see lost wax
casting |
| Cloisonné |
A type of enameling in which enamel (powdered
glass) is placed and fired between strips (Cloisons) that form
borderlines. |
| CMC |
Methyl cellulose, used as glue or binder. Available through pottery
shops. |
| COE |
Coefficient of expansion. A measure of how much a material contracts
when it heats and expands when it cools. Most glass that
kiln-forming artists use has a COE in the range from 84 to 104.
When fusing or casting, it is necessary to use glass with similar
coefficients of expansion. Click
here for a detailed discussion of COE and glass compatibility. |
| Combing |
A process where glass is manipulated at high temperatures in the kiln
by raking or drawing a tool across the surface of the glass.
Combing usually takes place at 1650 to 1700F. Lines are often drawn through multicolored glass when it is
in liquid state, producing a combed or feathered appearance. Click
here to read more about combing. |
| Cold working |
A collective term for techniques used to alter, decorate, or create a
texture or pattern in glass. Cold working takes place at room
temperature. Techniques including grinding, polishing, engraving,
and cutting. |
| Colloidal |
A mixture in which particles remain in suspension in a surround
medium. |
| Color reaction |
Many red and yellow colors react chemically when in contact with blues
and greens. As a result a brown or black border is formed. A color may
react also to impurities of glass or in kiln atmosphere. |
| Compatibility |
A measure of how well two different glasses "fit"
together. Compatible glasses can be fused together without
cracking or breaking when they cool. Click
here for a detailed discussion of COE and glass compatibility. |
| Compatibility test |
A test to ensure that two or more different glasses are compatible and
can be fused together. A polariscope is
used in most compatibility testing. Click
here to read more on compatibility testing. |
| CTE |
Coefficient of thermal expansion. See COE |
| Cones |
A temperature indicator. Cones are made for different temperatures.
The cone bends when that temperature is achieved. Because of its
mass, it takes some thermal work to bend a cone. In a fast ramp up a
cone may react later than in a slow ramp. Useful for testing evenivity. |
| Confetti |
Small thin shards of colored glass used as decorative element in
fusing. |
| Controller |
A programmable device that regulates the heating and cooling of the
kiln. The program consists of segments that
determine the stages |
| Crash, or crash cool |
To open (or vent) the kiln in order to allow it
to cool quickly from a fusing or slumping temperature to the annealing
temperature. |
| Crystal |
1. Glass: Glass which is very clear and refracts light. A crystal
glass contains 35 per cent or more lead and is not suitable for food
bearing surfaces. There are modern crystal like glasses that are free of
lead. See Lead Glass.
2. Chemistry: A solid form of material where atoms are ordered in
regular lattices. |
| Cullet |
1. Chunks of glass larger than frit. Often used
for casting
2. Pieces of scrap glass intended for recycling. |
| D |
|
| Devit |
See devitrification. |
| Devitrification |
A scummy, generally unattractive surface appearance that is difficult,
if not impossible, to reverse. Devitrification occurs when glass
molecules start to crystallize as they cool. It
usually takes the appearance of a whitish scum on the top edge of the
glass being fired. Most glass artists consider it to be a nuisance to be
avoided, but some like the effect and use it in their glass projects. It
is most likely to occur at above 1300 degrees F; for this reason, it’s
a good idea to minimize the time glass spends above that temperature. |
| Diatomaceous Earth |
A mold refractory material sometimes used
for molds. Diatomaceous earth is
fossilized diatoms that are ground up. Sold for swimming pool filters. |
| Dichro |
Shorthand form of dichroic. |
| Dichroic |
A type of glass in which a multi layer coating is placed on glass
using a process called vacuum deposition. Dichroic glass, which
can be coated with up to 30 layers of crystals and metal oxides, is
unique in hat it has a transmitted color and a completely different
reflective color. The colors can shift depending on angle of
view. Click here to learn
more. |
| Draping |
See slumping |
| Dremel |
A brand of handheld mini drill. Click
here to visit Dremel's website. |
| Drip casting |
see pot casting |
| Drop Ring |
A mold that has a large hole in the middle (like a donut). The glass is slumped through the ring until it
reaches the kiln self. |
| Dwell |
UK English term for soak |
| Dye |
A coloring agent that is in liquid form. See Pigment. |
| E |
|
| Elements |
Wires or tubes in kiln where the electric energy is turned to heat. |
| Elmers |
A brand name for PVA glue. (Also known as white glue.) |
| Enamel |
A mixture of flux, often finely ground glass and metallic oxides, when
mixed with a binder and medium, becomes applicable as surface coat to
glass, metal or ceramic. Click
here to read more. |
| Engraving |
A type of cold working which involves grinding or sandblasting
onto the glass surface. Engraving generally cuts deeper into the
glass than etching. |
| Enclosure |
Glass blowing term: A glass form of different color is surrounded by
clear glass. Can be done in kiln casting, too. |
| Etching |
A technique for cutting into the surface of glass.
Traditionally, etching was done with hydrofloric acid, but less
hazardous materials are available today. Etching can also be done
by sandblasting. |
| Evenivity |
A term that refers to the degree of uniformity of temperature inside the
kiln. In general, an even temperature through the kiln is
preferable to hot and cold spots. The term was coined by artist
Brian Blanthorn of Great Britain. |
| F |
|
| Fiber Board |
1/4"-1" stiff board made of mineral fibers. Used as
insulation in kilns but also to carve molds. |
| Fiber paper |
Heat resistant paper or cardboard-like material made of ceramic
fibers. It is used to prevent glass from sticking to kiln shelf. |
| Finding |
Jewelry: A fixture to attach a piece of jewelry to clothes or person. |
| Fine silver |
Jewelry: 99.9% pure silver; generally not used for large pieces in
jewelry because it is very soft; many jewelers use fine silver bezel
wire for setting stones in silver pieces See
sterling silver |
| Fire Polishing |
Shining the surface of glass by heating it until it smoothes out, the
edges round, and a shiny surface results. Fire polishing takes
place in a kiln at 1250 to 1350F (670 to 730C), depending on the type of
glass. |
| Flashing |
A ridge formed onto a cast piece due to mold seams or cracks.
Usually undesirable. |
| Flashed glass |
A multi-layered glass, usually with one or more colored glasses
applied over top of a clear or colored base glass. Click
here for more about flashed glass. |
| Flask |
Casting: a reservoir made in the mold above the model. Connected to
the model with a sprue. |
| Flat bed grinder |
A grinding machine with a horizontal rotating plate. The plate may be
metal and used with abrasive, or a diamond impregnated disk. See
lap wheel |
| Flint |
Silicon dioxide, SiO2. A white mineral commonly used as a
refractory in mold-making. The term flint is commonly used in
Europe and Australia, in the US the term silica tends to be used
instead. |
| Flint Glass |
Old name for window glass (soda lime glass). |
| Float glass |
Window glass. It is made by casting a length of glass on molten metal,
usually tin. This has an effect that some tin oxide remains on one side
of the glass and affects some enamels. The tin side is prone to
"bloom", a discoloration similar to devitrification. |
| Floral former |
A narrow, tall mold used for draping .
The floral former is shaped similar to a stainless steel mixing
cup. Click
here to read more about using a floral former. |
| Flux |
1. Glass: When glass is formed, soda melts first forming a flux
that dissolves the crystals of the other ingredients. Fluxes reduce the
melting point of glass. Lead and borax are strong fluxes. Fluxes may
react with mould or kiln wash causing sticking in subsequent firings.
Some fluxes also evaporate slightly corroding the kiln elements,
especially in casting where hot glass is kept in a kiln over prolonged
time. The term is also used for overglaze.
Flux can be used between glasses to assist melting in a lower
temperature. Used also to lower melting temperature of colorant
body stains and glazes.
2. Soldering: A paste or liquid applied to the surfaces to remove
oxidation that could affect the strength of the joint and by wetting the
surface allows the solder to flow. |
| Frit |
1. Glass that has been crushed to small grains or powders.
Click here
for suggestions on ways to make your own frit.
2. Ceramics: a composite powder used in glazing. Some toxic or
otherwise difficult ingredients are entered into the glaze mix as frit.
A fritted composite does not release gasses in use. |
| Frit Casting |
A type of casting in which a mold is filled with frit, then heated to
full fuse to allow the glass particles to flow into the crevices of the
mold. |
| Frit wafer |
See powder wafer. Frit wafer is
generally considered to be an incorrect term. |
| Full fuse |
When the fusing has continued so long that the surface of the work has
leveled out. |
| Fusing |
Joining pieces of glass by partial or total melting.. |
| G |
|
| Glass types |
No exhaustive list can be given. In kiln working Soda
Lime Glass is most common. Lead Glass,
often called Leaded Crystal, is also suitable and often used for
casting, but it is very expensive. Borosilicate
glass is more common in lampworking. Click
here for a discussion of glass types used in kiln-forming. |
| Green ware |
A clay or ceramic object that is dried but not bisque
fired. |
| Grog |
Fired clay that is ground to a powder. In Europe called Chamotte. |
| Grozing pliers |
Specialized tool made for breaking off glass outside a cut line. |
| Gypsum |
A white mineral which is the main ingredient of plaster of Paris and
gypsum board. Its chemical name is hydrous calcium sulfate
(CaSO4)(2H2O). In Europe used as synonym for
plaster |
| H |
|
| Hand rolled |
A glass sheet made by rolling molten glass over a marver (flat table) with a heavy
metal rolling pin. Characterized by somewhat textured or wavy surface. |
| Heat work |
The speed of kiln processes depends of temperature and time. Often the
same effect can be achieved by a lower temp and longer time. |
| I |
|
| Inclusion |
Piece of material other than glass that is imbedded in the glass
during fusing or casting. Typical inclusions are metals such as
copper or gold, mica or other minerals, air bubbles, or found items such
as fiberglass strands or twigs. Click
here to read more about inclusions. |
| Infinite Switch |
A switch used to regulate a kiln which allows the user to set the
temperature at any point from off to high. Most household oven
switches are infinite switches. Compare to controller |
| Investment |
Generic term for the mold material used in casting. |
| Infrared |
A kind of radiation that is not visible to the naked eye, but which is
given off by any hot object. Infrared radiation is radiated from
glass when it is heated in the kiln. Excessive exposure to
infrared radiation may harm your eyes by causing cataracts or by
irritating the cornea. It's a good idea to protect your eyes when
peeking in a hot kiln by wearing glasses with infrared absorbing lenses
(such as welder's glasses, shade 2.0 to 3.0). The effect of
infrared exposure is cumulative over years. |
| IR |
Short for infrared radiation |
| Irid |
Shorthand term for iridescent. Iridescent glass, where the glass surface has thin metallic coating
that gives luster or colored reflections on the surface. See also Dichro |
| Iridescent glass |
Glass that has been coated with a thin metallic coating. The
iridescent coating for tested compatible glass (such as that made by
Bullseye or for System 96) is made to withstand
fusing temperatures, but some non-tested coatings will burn off when
fired above 1100F. |
| J |
|
| |
|
| K |
|
| Kanthal |
A special metal wire used in kiln elements.
Kanthal contains aluminum, and during the first firing a protective
aluminum oxide coating is formed. |
| Kaolin |
Ceramic: White high temperature clay that does not react with glass in
slumping and low fusing temperatures. Used in kiln
wash and mould mixtures. |
| Kiln |
An oven to fire glass and/or ceramics. A kiln may be top loading
coffin, front loading, or bell jar type. The requirements of glass and
ceramics are somewhat different but may kiln types can be used
successfully for both. A glass kiln works in lower temperatures but the
uniformity of heating and cooling are more important. A slumping kiln is
preferably wide, with top elements. A casting kiln must be higher and
benefits of both top and side elements. A ceramic kiln must go to
temperatures 1200-1400 C and are usually lined with bricks. |
| Kiln carving |
A slumping or casting process where the mould is not built over a
model but directly carved or built up. |
| Kiln casting |
Casting glass into a mold in a kiln. either by filling the mold with
frit or by dripping the glass from a flowerpot suspended above the mold. |
| Kiln sitter |
A safety device. It cuts off the power when a certain temperature is
achieved. |
| Kiln wash |
A paint like material used on kiln shelves and moulds to prevent the
glass sticking. See Separator. |
| Klyr-fire |
A brand of medium for enamels, which may be used as glue for
glass. It will fire off in fusing. Klyr-fire is manufactured by
Thompson Enamels. |
| L |
|
| Laminated |
1. Safety glass where a sheet of polycarbonate is bonded between two
sheet of glass. Used in car windshields, tabletops and buildings. The
polycarbonate laminate is strong and if the glass is broken, keeps the
pieces and shards in place. Fused or slumped glass can be laminated with
epoxy.
2. Window glass stacked and glued with UV glue. By stacking differently
cut pieces three-dimensional sculptural objects can be formed.
Essentially a cold working process. |
| lampworking |
A method of jewelry and bead making where the glass is melted not in
kiln but in open flame of a burner. |
| Lap grinder |
A lapwheel |
| Lapwheel |
Horizontal flat bed grinder. Some models have metal surface and used
with abrasive slug. Lapwheels may also have a diamond impregnated
surface. |
| Lead |
Pb. A heavy, soft metal. Poisonous even in trace amounts. Used in lead
glass. Lead oxides are also used as fluxes. |
| Lead glass |
Leaded glass. Heavy, fairly soft glass with a long working range.
Sometimes called Crystal Glass. |
| Leveling shelves |
In flat fusing air that is trapped under the glass tends to form
bulges into the glass. One of the main reasons is that if the shelf is
not perfectly level an air trap is formed. One can grind the shelves
level. Read further: Charlie's post @ http://www.warmglass.com/phpBB/viewtopic.php?t=4946 |
| Lime |
Calcium Oxide |
| Lost Wax |
A casting method where the mould is made over a wax original. The wax
is then melted and burned out leaving a mold chamber of the desired
shape. Lost wax molds allow for more complicated shapes than can be made
with many other mold types. Click
here for more about the lost wax casting process. |
| Ludo |
See luto. |
| Luto |
A plaster based mold mix that has been fired once and then ground
fine. Can be used as a refractory in a mold mix. |
| Lustre |
Ceramic: term for an oily or metallic gloss glaze. Compare to Irid |
| M |
|
| Machine rolled |
Machine rolling produces sheets by drawing molten glass between two
steel rollers. Smoother than hand rolled, may include some bubbles. |
| Magless |
A refrigerator magnet without the magnet. The Warm Glass website
has an annual "Magless Exchange" in which members exchange
small glass refrigerator magnets. Click
here for more about the Exchange. |
| Mandrel |
Jewelry: A steel pin around which glass beads are made. |
| Mask |
A coating that is painted, glued, or taped to the glass. Masking is used to
protect areas during sandblasting and etching. |
| Medium |
A liquid that carries enamel or paint pigment |
| Millefiori |
Italian: 1000 flowers. Millefiori are small glass pieces which have
been sliced from multicolored canes. They're often fused
together. The term mosaic glass is also used
to refer to these canes. |
| Molochite |
very fine ground Grog made of kaolin |
| Mosaic Glass |
Glass decorated by repetitive use of small multicolored pieces. |
| Mould |
Alternative spelling for mold, generally used in Europe and Australia. |
| Muller |
A handheld tool for grinding and mixing enamels. It consists of a flat
pad of glass with a handle. |
| Mummy Wrap |
A mold making technique, where small patches glass or mineral fiber
are wetted in plaster and pressed over a splash
layer to produce a thin and durable mould. |
| Muriatic Acid |
Diluted hydrochloric acid, available from hardware stores. |
| N |
|
| NiChrome |
A metal alloy used in kiln elements. Somewhat cheaper than kanthal. |
| Nucleation Point |
1. In devit: When crystals form from a liquid, the process begins from
some impurity that serves as nucleation point for the growing crystal.
Devit is crystallization of glass and grows from nucleation point. It
may be dirt, fingerprint, scratch or something crystalline.
2. In casting: The hardening of plaster is a crystallization process. In
mold mix old hardened plaster, grog, or luto particles serve as
nucleation points speeding up the setting process. |
| O |
|
| O |
Oxygen |
| Opal |
Glass that is opaque or milky. See transparent
and translucent. Some opals have crystals
within the glass and may strike or devitrify
when
reheated. |
| Open face mold |
A mold where the cast or slumped piece can be lifted off without
breaking the mould. |
| Overspray |
A flux that is sprayed or painted on a glass to prevent devitrification. |
| P |
|
| Pate de Verre |
A French term meaning "paste of glass." In the pate de verre
process glass powder is mixed with a binder to form a paste. This paste is pressed onto
the surface of a mold and fired until the grains of glass fuse
together. The term pate de verre is sometimes also used as a
generic term for casting. The term frit casting is sometimes used
to refer to work made with a similar process that uses glass frit
instead of powder. Click
here to read a more detailed description of the basic pate de verre
process. |
| Pattern bar |
A bundle of lengths of colored glass fused together. When sliced the
pieces can be used as repetitive elements. |
| Pb |
Cemistry: sign for lead. |
| Peeking |
Visually monitoring the process in the kiln through a peep hole
without opening the door. |
| Peep hole |
A small opening in kiln wall to look through |
| Photo resist |
Photosensitive material that can be used to mask images that are then sandblasted
or etched into the glass. Used also in silk
screen printing enamels on glass |
| Pigment |
A colorant that is solid particles and not liquid like dyes. |
| Plaster |
Calcinated gypsum. It sets hard when water
is added. Used as mold material Dry plaster powder can be used as
separator. |
| Plaster of Paris |
CaO4.1/2H2O. A hard form of plaster used for sculpture and mould
making. |
| polariscope |
An apparatus to visualize stress in glass. The piece to examine is
placed between two polarizing filters and illuminated from behind. When
light passes through this setup, stress areas are seen as bands of color
or intensity. One filter sheet and a pair of polarized sunglasses serve
as a polariscope. |
| Polishing |
Smoothing the surface to a gloss by using abrasives, fire polishing or
acid polishing. |
| Potash |
Potassium carbonate. |
| Pot casting |
The glass is placed into a flowerpot over a mould and pot
melted to fill the mould. |
| Pot melting |
Heating glass in a flowerpot until it flows through the hole and forms
a sheet on the kiln shelf. Further reading http://24.209.173.166:8080/magless/untitled1.html |
| Powder wafer |
A thin decorative element that is made by tack
fusing layers of powder that have been sifted onto the kiln
shelf. After fusing, powder wafers can be used as decorative
elements in other fused and slumped pieces. |
| Pyrex |
DuPont's brand name for heat tolerant borosilicate
glass used for kitchenware |
| Pyrometer |
A device for measuring the temperature inside a kiln. Most
pyrometers are based on the thermocouple principle. |
| Q |
|
| Quartz inversion |
A process that occurs in many mold materials when they are heated or
cooled. At approximately 573C/1063F, the silica molecules in the
material change form, causing rapid
expansion or contraction and introducing stress that can break the
mold. Some clays are especially susceptible to this process.
The detrimental effects of quartz inversion can be minimized by heating
more slowing through the inversion temperature range. |
| Quenching |
Rapidly immersing hot or molten glass into water. The thermal
shock that results breaks the glass into pieces. This process
is frequently used to make frit. |
| R |
|
| Raku clay |
Ceramics. Raku involves rapid cooling and the raku clay is very
resistant against thermal shock. Useful mould material when bisque
fired. |
| Ramp |
The rate at which temperature is raised or lowered in kiln, usually expressed
as degrees per hour |
| Reactive colors |
see color reaction |
¨ |
| Refractory |
Any material that can tolerate high temperature without burning.
Examples are fiber board, ground silica, and kiln brick. |
| Relief |
A flat sculptural form. Glass reliefs can be made by slumping
or casting. Casting glass provides a particular method of back relief,
where the image is on the back surface of a transparent glass. |
| Rigidizer |
A binder used to harden or rigidize forms made of soft ceramic fiber
material. Colloidal silica SiO2 and colloidal alumina are two common
rigidizers.. |
| Rod |
A round, solid piece of glass that's approximately 4 to 10 mm
thick. Most often used in lampworking, rods are approximately the
size of a drinking straw or pencil. Also called a cane. |
| Roll-Up |
A method that combines kiln-forming and glassblowing techniques. The glass
is first fused in kiln and then picked up ("rolled up") while hot and worked with
glass blowing techniques. Because the technique was first
popularized by Australian glass artists, this is sometimes called an
"Aussie roll-up". |
| S |
|
| Safety |
Avoiding risks of cuts, burning, electric shock, toxic fumes and
harmful dusts. Read further: http://www.gregorieglass.com/HS_C.htm |
| Safety Switch |
A switch that cuts off the power before or when the kiln is opened.
Mandatory in Europe. |
¨ |
| Sagging |
See slumping |
| Sand |
The main ingredient in glass making. The source of silica in the melt.
In principle it could be collected from the beach, but in practice
better quality is wanted with fewer impurities. Glass-making sand is
from selected deposits, and throughoutly washed, heated to burn off
organic impurities and screened for grain uniformity. |
| Sandblasting |
A process where an abrasive material is blown by pressurized
air. For glass, sandblasting is used to carve, etch, or clean the
glass. The most common abrasives used by glassworkers are aluminum
oxide and silicon carbide. In most cases, the air for sandblasting
is blown using a compressor. Click
here to go to a website with more information on sandblasting. |
| Segment |
A phase of controller program. Some controllers include in one segment
both a ramp and a soak time. Many controllers handle
these as separate segments. |
| Separator |
A compound that prevents the glass sticking to a mould or kiln shelf.
Kiln wash is a separator, as are talcum or unfired plaster. |
| Shard |
An irregularly shaped splinter of glass. |
| Sheet glass |
Glass purchased as flat sheets. It may be hand
rolled, machine rolled or float
glass. |
| Si |
Chemical sign for silicon |
| Silica |
Silicon dioxide, SiO2. A white mineral commonly used as a
refractory in mold-making. The term flint is commonly used in
Europe and Australia, in the US the term silica tends to be used
instead. |
| Silicon |
1. Si, an element that like carbon is capable of forming complicated
molecules.
2. A common name for a variety of silicon based materials. |
| Silicosis |
A lung disease caused by inhaling silica dust. A proper breathing mask
or respirator must be used when grinding glass, handling clay or fiber dust
etc. Read here for
more safety information. |
| Single thickness |
one layer of 3 mm (1/4") glass. |
| SLG |
See SLS |
| Slip |
Ceramic term, refers to watery clay that is casted into a
plaster mould |
| SLS |
Soda Lime Silicate glass. Most art glass, such as that made by
Bullseye, Spectrum, and Uroboros, is soda lime glass. |
| Slumping |
Heat-softened glass sheet bent by gravity into mould shape. Draping is
slumping over a mold, sagging is slumping into a mold. |
| Soak |
To hold the temperature of the kiln constant to ensure even heat
distribution within the glass. Soaking is also needed to give the glass
time to slump or fuse. |
| Soda lime glass |
Soda lime silicate glass. Most art glass, such as that made by
Bullseye, Spectrum, and Uroboros, is soda lime glass. |
| Spectrum |
Glass company known for System 96 tested
compatible fusing glass. |
| Splash layer |
Casting: In mould making some fine mold material is splashed over the
model to provide a fine and bubble free inside lining before the bulk of
mold material is added. |
| Sprue |
Casting: A duct in a mold to conduct glass into the mold chamber
and/or air and gasses out. |
| Sterling silver |
a mixture of 92.5% silver and 7.5% other material (usually copper).
Sterling is generally used for larger jewelry because of the hardness
that the copper adds to it. See fine silver |
| Strain point |
The lower end of the annealing range.
This is the place where the molecules in the glass finally
solidify. Below this temperature strain cannot be introduced into
the glass. |
| Stressometer |
See polariscope |
| Striking |
A process in which the color or transparency of a particular glass
changes after being fired in the kiln. In some cases this is
desirable, sometimes the effect
is not wanted. Red glass tends to strike more often than other
glasses. Click here for a
brief discussion of striking. |
| Stringer |
A long, thin strand of glass, roughly spaghetti shaped, and ranging
from 1-3 mm thick. |
| Sugar acid |
The basic ingredients are distilled water, very fine sugar, and
ammonium hydrogen difluoride. Used to etch
glass. Extremely dangerous |
| System 96 |
A line of glass for fusing marketed by Spectrum Glass and manufactured
by either Spectrum or Uroboros. Click
here to visit the System 96 website. |
| T |
|
| Tack fuse |
light fusing where the pieces are joined but the shape not changed.
See deep fuse. |
| Tempered |
A kind of safety glass, where tightly controlled stress is introduced,
having the effect that the interior of the
glass is under constant compression. If the glass is broken, the stress
is relieved making small shards that lack sharp edges.
Tempering is industrially done by blowing cold air over both sides
of a heated sheet. Chemical tempering is done by impregnating the
surfaces with a low COE flux. Borax Overspray has some effect in
this direction. See laminated glass. |
| Thermal shock |
A tendency of glass to break due to uneven heating/cooling. In thick
or large pieces the risk for thermal shock is greater and heating or
cooling must happen much more slowly. |
| Thermocouple |
Temperature sensing electronic component. The data given by a
thermocouple is displayed by the controller. |
| Thinfire |
Bullseye's brand name for very thin fiber paper. Most thinfire
paper is about the thickness of a sheet of writing paper. |
| Tile saw |
A cutting machine with a diamond wheel. |
| Tin bloom |
See bloom. |
| Tin side |
The side of float glass that in manufacture was
in contact with molten tin. The tin side can be detected with a special
ultraviolet
light. Click
here to read more about detecting the tin side. |
| Tinted |
A glass with slight coloring. |
| Translucent |
Glass that is slightly opalescent, letting the light pass through but not
fully transparent |
| Transparent |
Glass - clear or colored - that you can see through. See Opal |
| U |
|
| Undercut |
A protrusion in the mold wall that prevents lifting the cast out without
breaking the mold. |
| Upper annealing point |
The upper end of the annealing range.
This is where the molecules in the glass begins to soften when heating
or begins to return to solid form when cooling. |
| Uroboros |
Glass company which makes both System 96
glass and tested compatible COE 90 glass. |
| V |
|
| Venting |
Slightly opening the kiln, either to allow organics to escape while
heating (such as fumes from glue or from fiber products) or to cool the
kiln more quickly. For more effective venting some kilns have fans or stainless steel
cooling ducts. Click
here for more information about kiln venting systems. |
| Viscosity |
The resistance of liquid to flow. In glass, often used to refer
to the degree to which glass flows when heated. Molasses has a
high viscosity, water has a low viscosity. Viscosity is related to
temperature. |
| Vitrigraph |
A particular kind of kiln where pot melted glass can flow out through a hole
in the floor. It is used to make stringers and other forms when the
glass thread hardens in the air. |
| Volume control |
Controlling the time and temperature in the kiln in order to ensure
that the glass spreads out to the desired thickness. Achieving
proper volume control relies on understanding the tendency of glass in a
kiln to equalize thickness at 6 mm (1/4"). |
| |
|
| W |
|
| Wasser |
A brand of tested compatible glass manufactured for fusing and
slumping. Wasser Glass is made by Diamond Tech
International. Click here to
visit Diamond Tech's website. |
| WBS |
See Wet belt sander |
| Wet belt sander |
A tool used for grinding and polishing the edges of a piece of
glass. Both table top and floor models are available. |
| WG |
Abbreviation for Warm glass, refers sometimes to the process, sometimes to
the discussion board and sometimes to the Warm Glass website. |
| Whiting |
see Calcium
carbonate. |
| X |
| Y |
|
| Z |
|
