Hydrocal FGR-95

AVAILABLE IN 5, 25, AND 50LB OPTIONS IN THE DROPDOWN

• Mix Ratio Parts Water by Weight per 100 Parts Plaster: 30 by weight

USG Hydrocal® Brand FGR 95 Gypsum Cement is a high-strength gypsum cement specially
formulated for use with glass fiber for fabricating glass-reinforced architectural details. The alpha
hemihydrate gypsum-based material has low water requirements that results in high-strength,
high-density glass fiber-reinforced gypsum pieces. It is ideal for producing lightweight, thin-cast,
fire-resistant architectural casts.

With its superior fabrication flexibility – from simple cornices to ornate capitals and medallions
– USG Hydrocal FGR 95 Gypsum Cement effectively duplicates pieces formerly made of plaster,
wood, concrete and stone. USG Hydrocal FGR 95 Gypsum Cement overcomes building fire code
incompatibilities faced by many plastics – at roughly one-third the cost of filled polyesters.
Exceptionally quick setting (45 – 75 minutes), USG Hydrocal FGR 95 Gypsum Cement accepts
most coatings and finishes.

MIXING INSTRUCTIONS

Use potable water at temperatures between 70 °F (21 °C) and 100 °F (38 °C). Because variations in
slurry (USG Hydrocal FGR 95 Gypsum Cement and water mixture) temperature produce variations
in set time, it is important to keep both the USG Hydrocal FGR 95 Gypsum Cement 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 Hydrocal FGR 95 Gypsum Cement and the water prior to use for each mix.
The water-to-USG Hydrocal FGR 95 Gypsum Cement ratio is critical because it governs the
strength and the density of the final cast.

Sift or strew USG Hydrocal FGR 95 Gypsum Cement into the water slowly and evenly. Do not drop
large amounts of USG Hydrocal FGR 95 Gypsum Cement directly into the water as proper soaking
of the USG Hydrocal FGR 95 Gypsum Cement may not occur. USG Hydrocal FGR 95 Gypsum
Cement 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 Hydrocal FGR 95 Gypsum Cement slurry is one of the most important steps in
producing USG Hydrocal FGR 95 Gypsum Cement casts with maximum strength, absorption,
hardness and other important properties.

Mechanically mixed slurries develop uniform casts with optimal strengths. USG Hydrocal FGR 95
Gypsum Cement 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.

APPLICATION

USG Hydrocal FGR 95 Gypsum Cement slurry can be applied via hand lay-up, spray-up or solid casting
depending on the mold complexity, size and depth, desired surface finish and quantity needed.

The most common method to fabricate large and/or complicated open-mold architectural pieces
is to use the hand lay-up method. Using a brush, apply a thin face coat of USG Hydrocal FGR
95 Gypsum Cement slurry (without glass fibers) to the properly prepared mold to a maximum
thickness of 1/16 in. (1.6 mm). Take care to cover all surfaces with the face coat and as quickly as
possible. As the face coat starts to lose its gloss yet is still tacky (do not allow the face coat to be
hard and set), hand or brush apply a reinforcing coat of slurry with chopped glass fibers added,
or by alternating layers of slurry and glass fiber veil. The reinforcing coat slurry should be mixed
separately approximately 10 to 15 minutes after the face coat slurry. Use a brush to compact the
glass fibers into corners of the mold so no bridging occurs. Be careful not to push the glass fibers
through the face coat. The total thickness of reinforcing layers depends upon the targeted flexural
strength and weight of the finished cast part.

The spray-up method is best used for molds that are uncomplicated, or simplistic designs that
have high demand and need to be fabricated with higher daily volume output. Using a peristaltic
pump with a liquid accelerator pump and a spray gun mounted with a glass fiber roving chopper,
spray a thin face coat of USG Hydrocal FGR 95 Gypsum Cement slurry to a maximum thickness of
1/32 in. (0.8 mm), covering all faces of the mold. As the face coat starts to lose its gloss yet is still
tacky (do not allow the face coat to be hard and set), simultaneously apply a reinforcing coat of
slurry and chopped glass fibers. A roller or brush should be used to compact the USG Hydrocal
FGR 95 Gypsum Cement slurry and chopped glass fibers into corners and around any complicated
areas. The total thickness of the reinforcement coat depends upon the targeted flexural
strength and weight of the finished cast part. Follow all pump, hose and sprayer manufacturers’
recommendations for usage with water-based slurry and chopped glass fibers.

For molds of greater depths and simple design features without using glass fibers, the solid casting
technique can be used. Depending upon final weight, strength and installation considerations, it
is possible to mix USG Hydrocal FGR 95 Gypsum Cement slurry and pour directly into the mold
until the mold is completely full. Slight vibration just after pouring will help encourage air bubble
release. A brush can also be used to ‘puddle’ the slurry in the deeper parts of the mold to remove
air. This method rarely is used with chopped glass fibers already mixed in with the slurry as it is
difficult to achieve a fiber and air bubble-free face coat.

A second method of solid casting employs a displacement plug approach where a backside mold is
used to displace slurry in deeper parts of the mold. The result is similar to hand lay-up and spray-up
methods and tends to be a faster fabrication process than the previous methods with deep relief molds.

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 Hydrocal FGR 95 Gypsum Cement molds are safe from
calcination is 120 °F (49 °C). 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 Hydrocal FGR 95 Gypsum Cement 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 Hydrocal FGR 95 Gypsum
Cement should be used within six months of the manufacturing date located on the package.
Always follow handling and use directions and safety warnings on the package.

SDS