im Glas-Ofen La Fornace
Glass of a yellow-brownish color, translucid, in
which copper metal microcrystals are dispersed to
reflect a gold color, formed by devetrification
(separation from the molten mass during the cooling
step). It is prepared by melting the mixture of
transparent corlorless glass with the addition of
cuprous oxide and iron and lead oxides. Melting
takes place in a reducing chamber and the molten
mass should be cooled very slowly. Traditionally,
to obtain the best quality, once the mass is molten,
the oven is switched off and left to cool on its
own for several days. Once room temperature is reached
the crucible is smashed and the avventurina is found
under a layer of colorless oxidized glass.
Calcedonio Glass with multicolored hues, translucid
with opaque veins, obtained by adding to the molten
mass, say colorless transparent glass, a pigmented
mixture based on different oxides (generally copper,
iron, cobalt and tin) and metallic silver that also
contains a reducing component (carbon or whatever);
the mixture is partially blended with the molten
mass and the whole is then mixed after some time.
The coloring effect is given both by the dissolution
of the metallic oxides in the glass and by the formation
of small colloidal particles of metallic silver
and copper, smaller than the micro crystals.
One of the fundamental process of Muranese glassworks.
A very large number of types of applications can
be found for this, both functional and decorative.
The extreme viscosity of the molten glass allows
it to be drawn out a certain temperature, starting
from the end of the blower's pipe in long, narrows
pipes. When al layer of colored glass is superimposed
over a base of opaque glass it is possible to obtain
numberless variants of color and thickness in relation
to how the molten glass is drawn out. Suitably heated
rods are used in decorations of vases and figures.
All Murano glass factories have always used them
extensively with artistic results.
Glass whose surface is irregular to the touch due
to the use of chemical agents. Technically an "acid"
process is caused by the corrosion of the surface
of the glass that determines the disgregation of
the glass lattice with the formation of a rough
layer on the surface. This non-uniform layer causes
an effect of partial diffusion and reflection of
light. For its execution solutions of hydrofluoric
acid and ammonium fluoride in water are commonly
used. By varying temperature, time in the bath and
composition of the same it is possible to obtain
very varied effects. The parts of the glass surface
to be kept bright are coated with wax or some other
organic protective agent.
Decoration obtained by applying threads of lattimo
glass or vitreous paste round the body of the item
in a festoon-like wavy pattern, obtained by means
of a kind of metal comb called "maneretta" passed
uniformly over the surface. This technique goes
back to the ancient Egyptians and the Phoenicians
to decorate flacons and ampoules.
One of the oldest traditional processes already
in use in the XVI century. It is done by applying
under heat on the surface of an item a homogeneous
series of transparent colorless glass rods, with
the core of colored glass. The rods are previously
arranged on a metal plate, they are heated to the
melting point and a cylindrical item is then made
to roll over them so that they adhere to it. The
item is then finished as desired.
This is a glass consisting of two superimposed layers
of lattimo glass and of colored transparent glass
on occasion with the submersion of gold and silver
leaf so as to obtain an opaque effect. This is a
much simpler execution than that of vitreous paste
that involves more complex technical problems, and
began to be used during the 20s at almost all the
most important factories in Murano.
This is an ancient glass-making technique to make
objects consisting of distinct parts joined under
heat. Two or more elements of different colors are
prepared by modeling them into the overall shape.
They are then joined together very accurately and
finished as desired.
This is a white milky-like glass in which the opacity
is provided by the presence of micro crystals dispersed
in the in the matrix separated out when the molten
glass is cooled down. The microcrystals do not absorb
the light beams but reflect them, and thus determine
both the opacity and the white coloring. In the
Murano area they consist of calcium and sodium fluorides
and they are obtained by adding fluorine compounds
such as cryolite or fluorine spar, as well as zinc
oxide and alumina, to the glassy mixture. The lattimo
was introduced in the XVI century for items decorated
with multicolored enamels, especially refined and
rare. It was later used as a complement to other
types of process, such as the "reticello ". It fell
into disuse in the early Novecento
but it was given a new lease on life in the late
20s on the part of the better names of Murano glass
factories, such as Barovier & C., Venini & C. and
MVM Cappellin & C. The latter was the first to use
it without the addition of other colors for a series
of geometric vases exhibited at the 1927 Intentional
Exhibition of Decorative Arts in Monza. Later, during
the 50s, lattimo glass was adopted by almost all
the glass furnaces on the island and attained excellent
results in figures as well, as was the case of the
famous "Commedia dell'Arte" figures by Fulvio Bianconi
for Venini & C.
Full, not blown, glass, processed under heat by
modeling a block of glassy mass applied over the
tip of a metal rod. This process appears in Murano
for the first time in the late 20s on the part of
Flavio Poli at the I.V.A.M. furnace of Libero Vitali's
where he designed the first figures in full or "massello"
This kind of glass is obtained melting glass pipes
(=canna) of different color: a set of pipes is prepared
on a metal plate according to a given design, heating
them up they melt each other. The result is a multicolored
plate that can be used for different complemets.
This is one of the oldest processes known to man
the first examples go back to Roman times. Items
made in this way were already existed in the XVI
century. Making a murrina consists essentially in
preparing a sheaf of multicolored glass rods, arranged
so that its cross-section is according to a predetermined
design. It is then heated and when the melting point
is reached it is drawn out until the de-sired diameter
is obtained. After cooling, the rod obtained in
this way is cut up into small disks of variable
thickness, ranging from just a few millimeters to
a couple of centimeters, whose section has the previously
made design. They are now ready to be used in several
ways. Their use in the production of several kinds
of objects is done in two different ways: The first
consists in preparing on a metal plate a set of
murrine according to a given design, heating them
up and then making them adhere by rotation on the
surface of an item with a cylindrical shape, still
connected to the blower's pipe. After this the item
is finished as usual, on occasion coating it with
a layer of transparent colorless glass. The second
more suitable for the execution of dishes and bowls,
has the murrine arranged inside a die in refractory
material, trying to fill in the empty spaces with
glass powder so as to get a homogeneous mass. The
whole is then heated as appropriate so that the
murrine are welded together to form a single object.
After cooling it is finished with the grinding wheel
to remove any irregularities that may be due to
This is a colored opaque glass whose preparation
is based on the same principle as the lattimo glass.
In this case, however, white microcrystals are dispersed
in a colored vitreous phase. Others, differently,
are obtained with colored micro-crystals dispersed
in either a colorless or a colored vitreous phase.
In the first case lattimo is used (microcrystals
of calcium and sodium fluoride) or white enamel
(amore intense white completely opaque even in a
thin layer, generally obtained with micro-crystals
of arsenic and lead) dispersed in a transparent
colored glass. The white microcrystals, in addition
to making the glass opaque, soften the color of
the glass in which they are inserted, that must
contain a high percentage of coloring agents. In
the second case "cores" are used: these are semi-finished
crystalline structures based on lead antimonate
or stannate that are yellow or red. These are added
to the molten mass just before processing because
they are compounds that dissolve easily.
Pezzato (lavorazione a tessere)
This glass is like a patchwork with elements of
different colors and is obtained as follows: on
a metal plate a series of segments of flat rods,
according to a given design are arranged. The plate
is heated to take the segments back up to the melting
point: at this stage the set of molten fragments
is made adhere by rotation to the outer surface
of the vase still on the tip of the blower's pipe.
After the pieces have been joined together, they
are finished by appropriate smoothing over and modeling.
Glass with a spongy appearance, with a great many
air bubbles, to the point that it is almost opaque.
The homogeneous and refined molten mass (with no
air bubbles or impurities) is vigorously mixed in
with salts (generally sodium carbonate or bicarbonate)
that decompose due to the heat and liberate gases
(carbon dioxide) dispersed in the form of bubbles
of varying diameters.
This is a variant of the "filigrana" already known
in Murano in the XVI. It is obtained by joining
two conical vases under heat, covered externally
with thin colored rods, one arranged clockwise and
the other anticlockwise. A network is thus formed
with a rhomboid-like mesh. The rods with different
thickness, within each quadrangle, cause the characteristic
This is a process to get the same results as the
"acid" process without, however, the latter's negative
aspects, linked with the use of toxic substances.
Sand or alumina powder is sprayed onto the glassware
with a compressed air device. The impact of the
granules on the surface causes microfractures that
make it opaque. Sanding is marked to a greater or
lesser extent by an appropriate adjustment of both
air pressure and granule size. Used mostly on flat
panes, this technique has also found application
in the preparation of some drawings by masking some
of its parts.
This is a glass that imitates the effect caused
by long periods spent underground, typical of glass
objects found during archaeological diggings. During
manufacture, a mixture of several powders is dispersed
on the surface of the object at a temperature of
about 800 C. These adhere irreversibly and give
the special effect of opaqueness and coloring. To
improve adhesion the piece is heated again. The
powder mixture contains melting components (carbonates
or nitrates that decompose under heat and act as
binders; inert opaqueness (talcum, silica, etc.)
other coloring agents. This technique was introduced
in the early 50s.
This is a glass invented in the early 50s. The procedure
for its preparation was as follows: a large concentric-ring
murrina was made with two alternating colors; it
was then heated again and applied while hot to the
item being processed. After a first finishing step,
and after cooling, the item still with an irregular
shape was modeled and polished at the grinding wheel
with an extremely long and delicate operation. With
this complex and laborious technique, a limited
number of items was made, very rare and refined,
that for their essential shape and decor represent
the very best Muranese production, with a level
of quality that compares well with that of northern
Enamels wide spread in Murano since ancient time.
While up to the mid-nineteenth century every craftsman
made his own on the basis of very particular and
jealously kept recipes, it later became fashionable
to adopt vitreous enamels produced on an industrial
scale. They must have the following features: applied
cold to the item during manufacture, they must fuse
at a temperature lower than that of the glass, their
colors should not fade at high temperatures and
they should Ave a coefficient of expansion as close
as possible to that of glass to prevent breakages
during the cooling stage. Once the decoration is
finished, the item is placed in a small "muffola"
oven where it reaches a temperature of some 550/600
C to allow the enamel to fuse without deforming
the item. In the Novecento this technique was used
to make copies of ancient models, but a few exceptions.
This is a glass coated with a thick layer of colourless
transparent glass, or with a glass which has a colour
different from the one of the backing. It consists
of a layer of colored glass with the inclusion of
air bubbles and gold leaf, more rarely with the
subsequent application of rods in pulegoso glass,
coated with a colorless transparent layer about
one inch thick. Many Muranese glass factories extensively
took up this technique with very considerable results.
A glass invented during the late 30s it is based
on the traditional filigrana, technique with particularly
thin rods used in this case, joined one to the other
with especially refined alternating colors. On occasion
to enhance the surface even further, it was lightly
"battuto" at the grinding wheel.
This is a glass rod executed with the same procedure
as the "murrine". A sheaf of rods of different colors
is prepared with a given design, it is heated to
the melting point; two metal rods are then attached
at the ends of the molten mass while two maestros
draw it out and impart a movement of rotation. The
fluidity of the material is such that it can be
twisted at will to assume its characteristic spiral-like
shape inside. This type of object was already known
in Murano in the XVI century with the name of "a
retortoli " glass. The current name of "zanfirico"
is taken from the Venetian nineteenth century dealer
Antonio Sanquirico who proposed this process anew.