ASTM C1191-91

Designation: C 1191 – 91
AMERICAN SOCIETY FOR TESTING AND MATERIALS
100 Barr Harbor Dr., West Conshohocken, PA 19428
Reprinted from the Annual Book of ASTM Standards. Copyright ASTM
Standard Practice for
1
Safe Use and Handling of Ceramic Clays and Slips
This standard is issued under the fixed designation C 1191; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope which is well blended and deaired, is safer and more economi-
cal in the long run. Such a clay is ready to use; just wedge and
1.1 This practice describes a safe manner in which to handle
throw on the wheel or hand model.
ceramic clays and slips in order to minimize respiratory
3.6 Trimming Greenware:
exposure to dust.
3.6.1 It is best to trim greenware before it dries hard. Use a
1.2 This standard does not purport to address all of the
fettling knife and cut off the excess trim and seam line. Then
safety problems, if any, associated with its use. It is the
wipe smooth with a soft, wet sponge.
responsibility of the user of this standard to establish appro-
3.6.2 When it is necessary to trim dry greenware, first spray
priate safety and health practices and determine the applica-
the area that needs trimming with water (do not soak). Spray
bility of regulatory limitations prior to use.
lightly, let the water be absorbed into the clay, then spray again
2. Significance and Use
until it becomes fairly wet. When the clay is wet enough, cut
away the trimmings and smooth out with a wet sponge.
2.1 Crystalline silica, which occurs naturally in all ceramic-
3.7 Designs:
clay products, including slip, has been linked to possible
3.7.1 If working extensively on a piece, for example,
environmental health problems. These health problems may
engraving a low relief design, try to keep it wet as long as the
occur through long-term respiratory exposure to dust from the
work is in progress by spraying it with water every so often or
dry clay or dry slip mix, which may contain free silica.
by keeping it covered with a plastic bag during work breaks.
3. Procedure
3.7.2 Slip trailing is a safer alternative method for produc-
ing low relief designs. Take some slip in a jar or small
3.1 In order to use clay safely, dust producing procedures
container and add a small dash of thickener (for instance,
(dry mixing and sanding) should be avoided whenever mixing
plaster). When the slip becomes thicker, fill a slip-trailer bottle
or working with clays. This can be done very efficiently in
and use it to apply the low relief design on the piece.
either a small or large studio operation.
3.8 Reconstituting Trimmings:
3.2 Clay in the moist or slip form is considered nontoxic.
3.8.1 To safely reconstitute trimmings, avoid drying them
Always finish the work while the clay is still wet, using a wet
out. Collect them in a pail as they are produced, then cover
sponge; do not sand.
with water.
3.3 It is practically impossible to make slip from dry clay
3.8.1.1 Trimmings from Cast Pots or Engravings—These
without producing dust. For this reason, premixed slip is not
trimmings could be added to a new slip mix with a minor
only safer, but also better blended and quality controlled. Such
adjustment to viscosity.
a slip is ready to use; just shake or stir and pour into the mold.
3.8.1.2 Trimmings from Finished Pots on the Wheel or from
3.4 If it is necessary to mix slip from dry powder, make sure
Hand Modeling—When the pail is full of clay, empty contents
that the mixing tank is in a well ventilated area equipped with
on a plasterbat and let dry to throwing consistency.
a mechanical air-ventilation system. When dumping dry pow-
3.8.2 Small Operations—When working in a small opera-
der, use only a National Institute of Occupational Safety and
tion the easiest way to save the trimmings is to return them to
Health (NIOSH) approved particulate respirator for dust and
the plastic bag in which the clay was packaged. Depending on
replace it often. If the face side of the respirator gets dirty or
the dryness of the trimmings, a little water may be sprinkled
contaminated, replace it immediately. A safety equipment
2
into the bag and the clay may be wedged while in the bag. Seal
supply house is the best source of suitable equipment.
the bag and let it sit for a week or two, after which it is usually
3.5 Do not mix large quantities of clay from dry powder. It
ready for use. Take it out of the plastic bag and wedge
is very difficult not to produce dust. Commercial moist clay,
thoroughly; if it is too wet, wedge in some fresh clay until a
1 good throwing consistency is achieved. It is then ready to use
This practice is under the jurisdiction of ASTM Committee C-21 on Ceramic
Whitewares and Related Productsand is the direct responsibility of Subcommittee
...