For the past fifteen years ceramist Riccardo Gori has worked
on the development of crystalline glazes, which he uses in the
porcelain jewellery he makes with his wife, Silvia Ferraro.
Here, from his Tuscan workshop, he describes his methods:
The transparency and colours of my crystalline
glazes are well suited for use in jewellery. The
technique is such that it is not always possible to
obtain the same effect, which means that each piece is
completely unique. As I’ve worked on developing the
glazes, the biggest handicap has been the absence (in the
Italian ceramic tradition) of literature on them. Yet
I’ve managed to create a glaze suitable for my
needs. With proper firing and various devices I’ve found
that I can produce small objects that suit subsequent
mounting. The mounting is done with wires and metal
accessories and needs to be designed to ensure the jewel
is ‘portable’. All these are not minor problems. A ceramic
piece of jewellery must have many features to be a
beautiful object to wear, otherwise it will only appear
as a ‘tile’ attached to a wrist or sitting around a neck.
‘On a vertical surface, the low
viscosity of crystalline glazes is
a problem that, generally,
does not exist in traditional
pottery. To be fired the pieces
must be equipped with the
appropriate ‘catchers’, which
collect the flow of glaze’
For our jewellery designs we started with one constant:
the extreme fluidity of the crystalline glaze. It isn’t
possible to decorate the entire surface of an object,
otherwise the flow of the enamel will make it stick
to the floor of the kiln. Instead, we have created small
pieces or ‘tiles’ of porcelain that can be glazed only on
one surface and then fired horizontally. This, however,
caused constraints for our
design. Our solution was to use
more than one ‘tile’, which, in
turn, has made our jewellery
more interesting. To connect the
completed ‘tiles’ we use small
wires. These must pass through
holes formed within the body
of each one. This was another
technique that caused problems.
Firstly, we needed to orientate the
holes correctly so that, if for a
necklace, the ‘tiles’ would adjust
neatly around the neck. Secondly, the
holes can fill easily. Low viscosity
glaze, by capillarity, can easily
penetrate into them. Initially we made all the jewellery by
hand, but to solve these two problems the solution has
been to shape the ‘tiles’ with moulds for porcelain
casting. These moulds have to be made so that the ‘tiles’
come out of them with the holes already made, and so are
properly oriented. In this way the necklace is always well
composed, just as it was designed to be. If a piece breaks
or is ruined during firing, you can also easily shape
another. To reproduce a perfectly handmade piece is far
more difficult, due to shrinkage and the deformations that
occur during the drying and firing process.
The choice of porcelain as a material has also come
with challenges. There is the deformation of the porcelain
during the firing process; and the interaction of the
crystalline glazes with different kinds of porcelain.
The study of the
interaction with the glaze has required many tests. These
tests have also given me an opportunity to discover and
find nuances and different colour effects.
On a vertical surface, the low viscosity of crystalline
glazes is a problem that, generally, does not exist in
traditional pottery. To be fired the pieces must be
equipped with the appropriate (what we call) ‘catchers’,
which collect the flow of glaze onto the oven floor;
without those the pieces would be glued there. These
‘catchers’, which are placed on the bottom of the object,
are later removed. The best technique has been to fire
the ‘tiles’ horizontally. The chemical characteristics of
the enamel that I have developed make it relatively more
viscous and, for small surfaces, the superficial tension
of the glaze at the melting temperature restrains the flow
of the enamel, so it does not slide easily beyond the edge
of the workpiece. On small surfaces, such as our porcelain
‘tiles’, the glaze behaves like a water drop on the spout
of a teapot: it does not always fall away. For these reasons
the percentage of rejects, due to the gluing of the pieces
on the oven floor, is only about 3 percent. Finally, in some
examples, we have enriched individual tiles with an
application of gold – shiny or matt – by brush. The gold
is subsequently fixed with a firing at 800°C. On
completion, the piece glistens.
Ceramic Review | January/February 2016
