USG Superfine Casting

USG Superfine Casting Plaster is a high purity general purpose plaster that can be used in a
wide variety of applications including architectural ornamentation and dental use. The physical
properties can be varied depending upon the desired end use, while the use consistency can vary
from a practical range of 45 lbs. water/100 lbs. of plaster (20 kg water/45 kg plaster) to as high
as 100 lbs. water/ 100 lbs. of plaster (45 kg water/45 kg plaster).

USG Superfine Casting Plaster is noncombustible. With a coefficient of thermal conductivity (k)
of 0.25 to 4.0 depending on density and additives, USG Superfine Casting Plaster can help to
provide a high degree of fire resistance. When dry, USG Superfine Casting Plaster is electrically
nonconductive and makes a good insulating medium.

MIXING INSTRUCTIONS

Use potable water at temperatures between 70 °F (21 °C) and 100 °F (38 °C). Because variations
in slurry (USG Superfine Casting Plaster and water mixture) temperature produce variations in
set time, it is important to keep both the USG Superfine Casting Plaster and water in a stable
temperature environment prior to use. The higher the temperature of the slurry, the shorter the set
time. Conversely, the lower the temperature of the slurry, the longer the set time.

Weigh both the USG Superfine Casting Plaster and the water prior to use for each mix. The waterto-
USG Superfine Casting Plaster ratio is critical because it governs the strength and the density
of the final cast.

Sift or strew USG Superfine Casting Plaster into the water slowly and evenly. Do not drop large
amounts of USG Superfine Casting Plaster directly into the water as proper soaking of the USG
Superfine Casting Plaster may not occur. USG Superfine Casting Plaster should be fully dispersed
in the water prior to mixing. Small batches require less soaking time than large batches. See USG

IG503 Plaster Mixing Procedures for specific soaking instructions.
Mixing USG Superfine Casting Plaster slurry is one of the most important steps in producing USG
Superfine Casting Plaster casts with maximum strength, absorption, hardness and other important
properties.

Mechanically mixed slurries develop uniform casts with optimal strengths. USG Superfine Casting
Plaster can be mechanically mixed through both batch and continuous processes. Proper blade
and bucket dimensions are important for obtaining the best batch mix (see USG IG503 Plaster
Mixing Procedures for details).

Longer mixing times result in higher mold strength and shorter set times.

POURING

To prevent air entrainment and provide a uniform, smooth surface, careful pouring of USG
Superfine Casting Plaster slurry is necessary. Agitation/vibration of the filled mold is a further step
used to prevent air at or near the mold surface. Whenever possible, USG Superfine Casting Plaster
slurry should be poured carefully in the deepest area so that the slurry flows evenly across the
surface of the case mold.

Pouring a large amount of slurry directly on the face of the case mold may result in slight
densification of the USG Superfine Casting Plaster mold at the point where it strikes the surface of
the case. This produces a hard spot, giving uneven absorption.

DRYING

All casts should be dried as quickly as is safely possible after manufacture so that maximum
physical properties can develop. Dry to a constant weight.

The best drying rooms or ovens provide 1) uniform and rapid circulation (minimum of 15-30 fps
(4.6-9.1 mps)) of air with no “dead spots” having little or no air movement, 2) equal temperatures
throughout the entire area, and 3) provisions for exhausting a portion of the air while replacing
it with fresh air. High humidity surrounding the drying room or oven inhibits drying efficiency
because the air pulled into the room is incapable of picking up much moisture from the molds.

The maximum temperature at which USG Superfine Casting Plaster molds are safe from calcination
is 120 °F (49 °C). With substantial free water in the mold, a higher drying temperature can be used
without difficulty. As drying progresses, the temperature must be reduced to prevent calcination.
Before removing molds from the dryer, the temperature should approach that of the area around
the dryer to prevent thermal shock. See IG502 Drying Plaster Casts for additional information.

STORAGE AND USE

When properly used, USG Superfine Casting Plaster is easy to work with and complies with the
federal Labeling of Hazardous Art Materials Act, 12 U.S.C. Section 1277 and ASTM D4236. Keep
indoors at temperatures between 65 °F - 75 °F (18 °C - 24 °C) and 45% - 55% RH. Do not stack
more than two pallets high. Keep from drafts. Rotate stock. USG Superfine Casting Plaster should
be used within 6 months of the manufacturing date located on the package. Always follow
handling and use directions and safety warnings on the package.

SDS

TDS