| Orton Firing Tip: Making Foodware Safe |
Reprinted with the permission
of the Edward Orton Jr. Foundation
When making ware to contain food and beverages, it is very important
to be sure it is foodsafe. Some of important considerations for mugs,
serving pieces and dinnerware include:
- body composition
- design of the ware
- glaze selection
- decoration
- firing to maturity
- government regulations
What Type of Ware?
The design of some pieces of ware have inherent problems which make
them unsuitable to contain food and beverages.
Design-related cracks, rough areas, crevices and nooks and crannies
are difficult to clean and might trap bacteria. They can also be difficult
to thoroughly glaze. Pitchers with hollow handles can have the same
problems.
Ware also needs to be serviceable that is, it should be strong so
it won't fail or break during service.
Making Smart Glaze Choices
While glazes are extremely durable, most are not completely insoluable.
If attacked by acids in foods such as orange juice, vinegar and tomatoes,
small amounts of the glaze may dissolve and pose a health hazard.
Acid resistant glazes have passed rigorous tests and are labeled as
foodsafe. These should be selected for glazing food ware. Lead-free
glazes may not be acid-resistant and should not be used unless labeled
as foodsafe.
Homemade, altered, crackle, matte or specialty glazes also should
be avoided for surfaces of containers that will contact food and beverages.
How to Decorate
When glazing, be sure to completely glaze the ware to ensure the entire
body is sealed. Properly bisqued porcelain may be dry footed, but
only if the porcelain has been fired to vitrification. Label the ware
as foodsafe for future users.
China paints, decals and rim designs are a popular way to decorate
plates and mugs, but may not be safe for food surfaces. Specific regulations
exist for the location of rim decorations which must be followed.
Decals should be used on the outside of a piece where they will not
be in contact with food or beverages. Use china paints on decorative
items only.
Safe Firing
Proper glaze firing and the bisque firing are very important to insure
ware is foodsafe. If the bisque is underfired, it may create problems
with glaze and body fit that result in crazing of the glaze, or glaze
surface defects such as pinholes. These would not be acceptable for
ware used to contain food and beverages.
If the glaze is not properly matured, it will not meet the foodsafe
standards under which it was tested and may craze while in service.
Using pyrometric witness cones on the kiln shelf is the only way to
insure that a proper firing has occurred. For foodsafe ware, many
prefer to fire their bisque to an 03 witness cone just to be sure
it is fully mature. Read and follow the manufacturer's instructions
for glazes for the best and safest results.
Regulations
There are several very specific regulations for ware which will contain
or contact food and beverages. California has the most stringent rules
for dinnerware and new standards have been set by the FDA for rim
decorations. These rules are available from state and federal agencies.
If you are selling your dinnerware you may be subject to additional
regulation.
How to Test for Lead Release
Several easy to use products are available on the market to test for
lead release. These are primarily quantitative tests - that is, they
tell you yes or no if the surface has lead above a certain level.
The most commonly used kit is a thick cotton swab which turns pink
if lead levels are exceeded. This test does not harm ware so if it
tests too high in lead, the piece can still be used as decoration.
These tests are a simple, economical way to feel confident that your
ware is safe.
Want to learn more?
Read more about Making Foodware Safe in the Orton Firing Line and
Technical Tips publications. Each issue is packed full of articles
to help you learn more about firing. Members of the Orton Firing Institute
receive these publications at no charge. Single copies are available
to non-members at a per issue rate. Orton's 80 minute video, Key
Principles of Successful Firing, is also an excellent resource
on firing.
For information on Orton products, see your Orton dealer or distributor.
For information on the Firing Institute or publications, contact:
Orton Firing Institute
PO Box 460
Westerville, OH 43086
(614) 895-2663 |
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