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Page Contents:
-What is enamelware
-What is graniteware
-What is agateware
-Making porcelain enamel
-Final coatings
-Enamelware and high heat
-Coating & metal thickness
-Enamel surface
-How to clean enamelware
-Enamelware and corrosion
-Enamelware as heat conductor
-Enamelware is recyclable
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Enamelware Guide
What is enamelware?
Enamelware is made with a base metal of steel, iron or aluminum that is
covered with a glass-like material called porcelain enamel. It is also
referred to as porcelain on steel, cast iron enamel, vitreous enamel,
agateware, and graniteware. The process is thousands of years old, found in
many cultures and of unknown origin. Mass production of enameled kitchen
utensils started in the latter part of the 19th century in the Americas.
What is graniteware?
Graniteware is a type of enamel, and is so named because its composition
also includes granite, from which it gets its particular coloration. This
process was started and patented by the Niedringhaus brothers in 1874, in
the city now known as Granite City, Illinois.
What is Agateware?
Agateware is indicative of the design, generally with variegated curved and
colored bands and other markings.
Making Porcelain Enamel
The process of making porcelain enamel begins with clays, electrolytes,
metal oxides and water, just as in making glass. The mixture includes
materials such as borax, feldspar, quartz and titanium dioxide, which are
liquefied at very high temperatures. Poured from a smelter, the mixture is
quenched between water-cooled rollers to form a quick-cooled ribbon of
glass, which is then shattered to form a particulate known as frit. Frit is
applied to metal using either a wet dipping or spraying, or a dry method,
generally in multiple coatings, then fired at very high temperatures
(932-1652° F). While in the furnace, the frit melts, bonding with the metal
to create an inseparable compound, resulting in a new, chemically unique
finish.
Final coatings
The final coatings of frit usually include color and determine appearance
(smooth, pebbly, stippled, matte or glossy). Pigments, primarily inorganic
compounds fused into the glass matrix, are extremely stable during aging.
While glossy, acid resistant porcelain enamels are not photosensitive,
matte-finish and some types of highly pigmented red and yellow porcelain
enamels may show some fading after several years of weathering, and alkali
resistant porcelain enamels are not necessarily acid resistant.
Enamelware and High Heat
Enamel can usually be safely subjected to high heat, and can generally take
abrupt temperature changes of 200-300° F without damage. Although very hard,
a thin coating (1-mil or less on steel or aluminum) can flex more with the
base metal as it expands and contracts with heat and cold. A thick coating
(125-mils or more) can be effectively used over iron and heavy gauge steel,
as its rate of expansion and contraction is much less than that of thinner
metals.
Coating and Metal Thickness
The thickness of both the metal and the coatings is one of the most
important determining factors in the longevity of porcelain enamel.
Generally, a thinner coating will have greater flexibility and a lesser
likelihood of fracturing. Porcelain enamel becomes as hard as the base
metal, and will not break unless the base metal fractures or becomes
deformed. Its hardness is generally measured from 3.5-6 Mohs (organic
finishes in the 2-3 range), and its compressive strength is in the range of
20,000 psi.
Enamel Surface
Enamel is usually quite even and smooth, very resistant to abrasion, does
not rust or burn, and retains its original gloss and color. It is completely
resistant to attack by common organic solvents, dyes, greases and oils, it
is non-porous, impervious to bacteria and most chemicals, and very easy to
clean. Its dense surface makes it the second most stick-resistant material,
next to fluoropolymers.
How to Clean Enamelware
Most cleaning can be performed using only water and a mild detergent.
Boiling water in the pan and letting it soak can usually loosen sticking
food, which can then be removed with a nylon scourer or wooden scraper. The
build-up of lime and calcium deposits from water may be removed by boiling a
solution of vinegar and water.
Boiling water with baking soda (2 tsp per quart) can be effective for tough
tasks. Cleaning stubborn sticking and stains can also be accomplished by
using 1 tbsp trisodium phosphate to 1 quart of hot water, or soak 2-3 hours
with a solution of 1 tsp of bleach per pint of water. Acetic and muriatic
acids are effective in removing certain stains, but they will also remove
part of the surface coating of the porcelain.
If you must use scouring powder it should be of the very finest grit, such
as Bon Ami or Bar Keeper's Friend. For heavy baked-on grease, or spills, you
can occasionally use a fine steel wool pad or scrape with a razor blade,
however do not scratch the enamel, or it will be harder to clean afterwards.
If you use chlorine or hydrogen peroxide bleach, do not use these full
strength or let them remain on the surface for more than a few seconds.
Rinse the surface thoroughly.
Enamelware and Corrosion
Enamel can corrode through repeated or prolonged contact with acidic
elements. Boiling water slowly damages enamels over a long period of time,
and soft water will corrode enamels faster than hard water. Enamel will
easily withstand repeated freezing and thawing of liquids, however over time
this will cause some lesser quality enamels to chip or splinter.
Special paints are available to repair enamel, however these should not be
used on cooking utensils.
The enamel finish on many appliances (refrigerators, the sides of stoves,
and other appliances that are not subjected to high heat) is usually
synthetic, or may be applied by an electrostatic process called powder
coating. Although very hard, its thinness does not have the same
scratch-resistant properties as regular baked-on enamel.
Enamelware as a Heat Conductor
Enamel is a relatively good heat conductor when applied in thin coats,
however it is not a thermal insulator or diffuser. Avoid over-heating and
pre-heating empty, and use a heat diffuser under enameled pans made of thin
steel and aluminum.
Enamelware is recyclable
Enamel does not hinder the recyclable nature of the material that it covers. |
