It is fascinating to note that some of the techniques for shaping and colouring
glass were lost and rediscovered over the centuries. So that glass from Egyptian
or Roman times is more ornate and complex than early medieval glassware's.
Until the later part of the 20th. Century, glass making was a closely guarded
skill. To a certain extent, it still is. As we no longer have secret guilds to
apprentice into trial and error still seems to be the main stay of learning to
work in glass. In Slumping, the glass is laid into, or on top of a mold and heated
just to the point where it "Slumps" to fit the form of the mold. Once the glass
reaches the desired form it must be cooled quickly enough to stop the
movement that will result in cracking. Although these methods sound
simple, the objects created are quite often very intricate in their design,
and hours of painstaking labour may go into the arrangement of the glass.
In many examples the glass has been fused into a pattern and then slumped to
fit a particular form.
Another category of glass work which requires a kiln involves the more
elaborates use molds to form glass into more complex shapes. Virtually any
shape that can be formed in clay or wax can also be made in glass .These
more advanced kiln forming processes include kiln casting like melting glass
into a mold inside a kiln, called "Pate de Verre" or "Paste of glass" and glass
casting is a pouring molten glass into a mold.
These processes tend to be more complicated than basic fusing and slumping.
They require working knowledge of basic fusing and slumping techniques and
processes. The finished product has more than one colours and the difference
of them can be seen when the glass is viewed from different angles. Technically
there are three colours in the finished piece transmitted when light passes
through the clear glass, reflected the light that bounces off the glass and
reflects a second colour, with the third colour viewed by looking at the glass
from a 45 degree angle.
Adding different metal oxides to sand, soda and lime, the basic formula for
glass creates different colours. For example greens and aqua glasses usually
have iron, while amber and brown colours are produced by adding small
amounts of iron and sulphur. Light blues require copper, while dark blues
require very small quantities of cobalt.
Amethyst glass contains manganese. Opaque white can contain either tin or
calcium. Selenium is one metal oxide that is used to produce reddish colours,
Some reds and pinks even have a bit of gold in them and he soft purples and
violets that gave the nickel oxide. Slumping is nearly synonymous with
sagging, however, slumping usually implies a bending without noticeable
change in thickness of the cross section of the glass. But by keeping the
temperature as close as possible and high enough to allow downward
movement an avoid stretching.
Sagging is the downward sinking of glass caused by its own unsupported weight
as the glass softness when heated. Sagging as a process whereby the
thickness of the glass cross section changes noticeably due to stretching. The
edges that overhand a mold will turn up as the middle sinks down as the slum
progresses, the edges fall and the mold fills and this is the reason why vent
holes are necessary in all non-porous molds and should be placed in the
areas of the mold fill last, the center of the bottom always fill first, therefore
is not the proper place for venting air trapped between the glass and the mold.
More slumped forms require to use of more than one mold as a deep bowl for
example is just about impossible to slump in one firing using a single mold for
that reason a series of different molds are used in order to maintain control of
the glass. Always as a rule you must take notes of the different stages while
you are working also with your design of different colours because they absorb
heat at different rates.
I hope all this information is useful. I want to share my experiences which are
challenging the rewarding. I learn from my failures and continue to strive to
understand the properties of glass during the firing (heating). My own
observations have permitted me to develop personal techniques in glass forming
through fusing and slumping.
I gently enjoy this glass techniques as a way for artistic creativity.
glass were lost and rediscovered over the centuries. So that glass from Egyptian
or Roman times is more ornate and complex than early medieval glassware's.
Until the later part of the 20th. Century, glass making was a closely guarded
skill. To a certain extent, it still is. As we no longer have secret guilds to
apprentice into trial and error still seems to be the main stay of learning to
work in glass. In Slumping, the glass is laid into, or on top of a mold and heated
just to the point where it "Slumps" to fit the form of the mold. Once the glass
reaches the desired form it must be cooled quickly enough to stop the
movement that will result in cracking. Although these methods sound
simple, the objects created are quite often very intricate in their design,
and hours of painstaking labour may go into the arrangement of the glass.
In many examples the glass has been fused into a pattern and then slumped to
fit a particular form.
Another category of glass work which requires a kiln involves the more
elaborates use molds to form glass into more complex shapes. Virtually any
shape that can be formed in clay or wax can also be made in glass .These
more advanced kiln forming processes include kiln casting like melting glass
into a mold inside a kiln, called "Pate de Verre" or "Paste of glass" and glass
casting is a pouring molten glass into a mold.
These processes tend to be more complicated than basic fusing and slumping.
They require working knowledge of basic fusing and slumping techniques and
processes. The finished product has more than one colours and the difference
of them can be seen when the glass is viewed from different angles. Technically
there are three colours in the finished piece transmitted when light passes
through the clear glass, reflected the light that bounces off the glass and
reflects a second colour, with the third colour viewed by looking at the glass
from a 45 degree angle.
Adding different metal oxides to sand, soda and lime, the basic formula for
glass creates different colours. For example greens and aqua glasses usually
have iron, while amber and brown colours are produced by adding small
amounts of iron and sulphur. Light blues require copper, while dark blues
require very small quantities of cobalt.
Amethyst glass contains manganese. Opaque white can contain either tin or
calcium. Selenium is one metal oxide that is used to produce reddish colours,
Some reds and pinks even have a bit of gold in them and he soft purples and
violets that gave the nickel oxide. Slumping is nearly synonymous with
sagging, however, slumping usually implies a bending without noticeable
change in thickness of the cross section of the glass. But by keeping the
temperature as close as possible and high enough to allow downward
movement an avoid stretching.
Sagging is the downward sinking of glass caused by its own unsupported weight
as the glass softness when heated. Sagging as a process whereby the
thickness of the glass cross section changes noticeably due to stretching. The
edges that overhand a mold will turn up as the middle sinks down as the slum
progresses, the edges fall and the mold fills and this is the reason why vent
holes are necessary in all non-porous molds and should be placed in the
areas of the mold fill last, the center of the bottom always fill first, therefore
is not the proper place for venting air trapped between the glass and the mold.
More slumped forms require to use of more than one mold as a deep bowl for
example is just about impossible to slump in one firing using a single mold for
that reason a series of different molds are used in order to maintain control of
the glass. Always as a rule you must take notes of the different stages while
you are working also with your design of different colours because they absorb
heat at different rates.
I hope all this information is useful. I want to share my experiences which are
challenging the rewarding. I learn from my failures and continue to strive to
understand the properties of glass during the firing (heating). My own
observations have permitted me to develop personal techniques in glass forming
through fusing and slumping.
I gently enjoy this glass techniques as a way for artistic creativity.
Glass Technique Slumping
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Tools for Slumping