ARMCHAIR POTTING.
FRITS.
Why are they so many different frits in the ceramic supply shops?
This question one hears a hundred times over and over again. The answer is
quite simple each frit is designed for a specific application. It may be for
Ceramic glazes (clear, opaque coloured etc.) metal enamelling and also "fritted
porcelain". Some frits are designed to provide flux in the manufacturing
of vitrified grinding wheels.
In the old days many ceramic manufacturers made their
own frits - designed for their specific purpose i.e. firing range and temperature,
colour tolerance to metallic oxides, thermal expansion characteristics etc.
All the freight formulas but kept in a safe so no stranger could get his hands
on it!
Since the end of the second world war things changed. Large ceramic supplies
offered to produce frits for any occasion at prices which were very attractive
and therefore difficult to resist. Some of the manufacturer's traded world-wide
establishing their branches also in Australia. I remember Ferro Corporation
in 1950 starting in Sydney and I believe Blythe established a place in Melbourne.
At the same time Cesco an Australian company started by Russell Gowen in Hornsby
Sydney producing many Frits as well as clay bodies, casting slips and refractories.
Ferro frits are probably the most popular ones among Australian Potter's.
We only wish they would stop changing the numbers as soon as we remember them
they change them again!
| KGF 4064 | A lead frit useful for clear earthenware glazes |
| KGF 4101 | A frit for metal enamelling and also very popular for raku glazes |
| KGF 4108 | A soft frit for raku glazes |
| KGF 4110 | A high sodium frit for manganese purple and copper blue |
| KGF 9102 | A zircon frit for maiolica decoration |
| KGF 4112 | A calcium borate frit which replaces the mineral colemanite |
Of course we can make our own frits for special occasions. During the war the German industry was short of "borax flux" used during soldering in the electrical production of all types of instruments . To overcome the shortage they developed a flux (frit) based on equal molecular parts of Soda Ash ( Dehydrated, double strength - available in supermarkets), Titanium Dioxide and Silica.
| Recipe | ||
|
|
Sodium Oxide (to be supplied by sodium carbonate) |
43.1% |
| Titanium dioxide | 24.4% | |
| Silica 200 | 32.5% | |
| 100% |
Mix all the ingredients dry, place the mixture into a crucible (fired) made from raku body, and fire it in a raku kiln to 700-800oC. Pour the resulting melt into a metal bucket full of water. Crush the frit in a mortar and pestle and weigh up an experimental glaze using the following suggestions:
| Glaze | To this glaze add metallic oxides of |
| Frit |
100
|
Copper
|
2 - 5% or |
| Bentonite |
5
|
Cobalt
|
.5 - 2% or |
|
Chrome
|
.5 - 3% or | ||
|
Manganese
|
2 - 6% or | ||
|
Iron
|
4 - 8% etc. |
Fire the samples in a raku kiln to approximately 700oC or higher until you see that the glaze has matured. I the frit has been properly prepared you could fire as low as 650oC.
Cheerio for now
Mike