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  #1 Moulding Plaster 50 Lbs.

U.S. Gypsum #1 MOULDING PLASTER 50 lbs. Bag
U.S. Gypsum #1 MOULDING PLASTER 50 lbs. Bag

U.S. Gypsum #1 MOULDING PLASTER 50 lbs. Bag
Our Price: $20.00

Product Code: RMMOUPLA50

U.S. Gypsum #1 MOULDING PLASTER 50 lbs. Bag


An ornamental plaster used for creating decorative trim or running cornices.

Designed for use where expansion control, hardness and strength are not primary considerations.

Often referred to as plaster of Paris or soft plaster, USG® No. 1 moulding plaster is used to create waste molds or temporary patterns where surface hardness and strength are not crucial. USG No. 1 moulding plaster:

  • Offers a controlled set that provides uniform workability
  • Has a fine grain – making it ideal for producing sharp detail when used neat for cast work
  • Complies with ASTM C28
  • Sets in 27-37 minutes after mixing
  • Requires 70 parts water by weight per 100 parts plaster
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Almost always one of the lowest cost solutions to your industrial product and process
problems or product development opportunities
▪ Simplify a variety of manufacturing
▪ Easy to use and handle
▪ Retain desirable physical properties

Plaster provides a controllable setting performance
few other materials can offer. By adding
accelerators or retarders, you can shorten or
lengthen its setting time and reproduce setting
time from batch to batch.

Controllable setting time . . .
▪ Gives you a broad choice of working times,
ranging from about 3 minutes to 20 hours
▪ Maximizes production rate
Note: Plaster sets with a sharp, definable, measurable
action. It sets fast—faster than typical portland
cements and other cementitious materials.

Controllable expansion
Only plaster among cementitious materials offers
controllable expansion—ranging from 0.0005 to
0.0156 in. per in. (or 3⁄16 per ft.). Plaster formulations
can come closer to zero expansion than
many other materials.
Controllable expansion . . .
▪ Ensures high dimensional accuracy
▪ Ensures duplication of fine detail
▪ Provides a positive mechanical key when
poured into a cavity.

Ease of Use:
Plaster can be fabricated or used in four main
1. Mixed as a fluid slurry, it can be cast or
2. Worked in a plastic state by screeding or template
3. Pressed between dies as a semi-wet powder
4. Carved or machined as a solid
In fluid slurry form, plaster pours easily into
flexible or rigid molds. Viscosity ranges from
nearly water to molasses. Plaster captures fine
detail and can be parted from any nonporous
surface. Properly formulated, it can be self-leveling
and pumpable.
In plastic mass form, plaster can be built up,
troweled, added to, scraped away, or sculpted as
easily as clay. Viscosity ranges from that of
butter to modeling clay, or plaster can be applied
as a plastic mass to virtually any contour—and
will set in place to produce a reverse contour.
In solid form, casts from plaster formulation can
be carved or machined using conventional tools
and equipment, including numerically controlled
milling equipment.

Only gypsum among commercial materials possesses
extreme ranges in strength, absorption,
and density. For example:
▪ Compressive strength (and hardness) can
range from that of weakest chalk to four times
greater than concrete
▪ Absorption can equal that of a rigid sponge or
an impervious surface that sheds water
▪ Density can vary from that of popcorn to stone

This great range occurs by selecting the
appropriate plaster formulation, then controlling
the amount of mixing water. The graph below
indicates how you can obtain this range through
predictable control of desired characteristics.

Only gypsum among casting materials is selfcleaning
in the mold—a basic requirement in the
ceramics industry. What gives gypsum this
advantage is its solubility (about two grams per
liter of distilled water).
Note: If reduced solubility is not required,
gypsum cements can be formulated to meet conditions—
it’s that versatile.

Industrial plasters and gypsum cements readily
blend with chemicals and aggregates to achieve
special properties. Both wet and dry blending
are done with various chemicals, powders, and
granular materials.
These include:
talc iron oxide kaolin
resins ball clay asphalt
perlite starches sand
dyes vermiculite pigments
wood fiber polymers foaming agents
powdered glue
set-time control additives
glass/polymer fibers

Compatibility with other chemicals, aggregates
Note: Except for special gypsum cement formulations,
do not use coarse aggregates (gravel, stone,
rip-rap, or any aggregate larger than 10 mesh) as
gypsum crystals do not readily bond to them.

Fire Resistance
Industrial plasters and gypsum cements are
noncombustible. With a coefficient of thermal
conductivity (k) of 0.25 to 4.0, depending on
density and additives, these materials provide a
high degree of fire resistance. When exposed to
heat, they do not exceed 212 °F until threequarters
of the chemically combined water is
driven off. At about 1800 °F the CaSO4 portion
dissociates into quicklime (CaO) and sulfur
trioxide (SO3). Dry gypsum is electrically
nonconductive and makes a good insulating

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