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Casting Product Index - Accessories Index
See also Gypsum Accelerator & Retarder

  HYDROCAL® Brand White Gypsum Cement

Hydrocal White

 

Click here for MSDS.
  • Setting expansion twice that of Moulding Plaster or Pottery Plaster.
  • High green strength for less breakage in process.
  • Ideal for both solid and hollow casting of lamp bases and figurines.
  • Good multi-purpose product.
  • Very white color
Technical Properties English Metric
Use Consistency (parts of water by weight per 100 parts plaster ) 45 45
1 Hr. Compressive Strength 1,000 psi 6.9 MN/m2
Dry Compressive Strength 5,000 psi 34.5 MN/m2
Maximum Setting Expansion 0.390% 0.390%
Density
Wet 110.0 lb/ft3 1.76 g/cm3
Dry 90.0 lb/ft3 1.44 g/cm3
Set Time (Machine Mix)* 25-35 min. 25-35 min.
*Other set times may also be available. Call your sales representative for more information.
 
General Directions and Guidelines

  Preparing the Mix Use potable water at temperatures between 70° and 100°F (21° and 38°C). Since variations in slurry (HYDROCAL® Brand White Gypsum Cement and water mixture) temperature produce variations in setting time, it is important to keep both HYROCAL Brand White Gypsum Cement and water in a stable temperature environment prior to use. The higher the temperature of the slurry, the shorter the set time. See the graph below.
 


 
  Measuring Weigh both HYDROCAL Brand White Gypsum Cement and water at the recommended use consistency for each mix (see Technical Properties above). The water-to-HYDROCAL Brand White Gypsum Cement ratio is critical because it governs all physical properties of the final cast piece.
 
  Soaking Sift or strew HYDROCAL Brand White Gypsum Cement into water slowly and evenly. Do not drop handfuls of HYDROCAL Brand White Gypsum Cement directly into the water. Allow soaking for 1-2 minutes. HYDROCAL Brand White Gypsum Cement should be fully dispersed in the water prior to mixing. Small batches require less soaking than large batches.
 
  Mixing

Mixing the HYDROCAL Brand White Gypsum Cement slurry is one of the most important steps in producing HYDROCAL Brand White Gyspum Cement casts with maximum strength, hardness, and other important properties.

Mechanically mixed slurries develop uniform casts with optimal strengths. HYDROCAL Brand White 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. Longer mixing times result in higher cast strength and shorter setting times. The relationship between mixing time and both compressive strength and setting time is shown below.

   
 
  Pouring

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

Pouring a large amount of slurry directly on the face of the mold may result in slight densification of the cast at the point where the slurry strikes the surface of the mold.

 
  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) 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 the efficiency of the drying because the air pulled into the room is incapable of picking up much moisture from the cast pieces.

The maximum temperature at which HYDROCAL Brand White Gypsum Cement casts are safe from calcination is 120°F (49°C). With substantial free water in the cast piece, higher drying temperatures can be used without difficulty. As drying progresses, the temperature must be reduced to prevent calcination. The safe drying zone is in the shaded area of graph (below, right). Before removing casts from the dryer, the temperature should approach that of the area around the dryer to prevent thermal shock.

   
 
  Storage Keep in a dry, stable environment indoors. Do not stack more than 2 pallets high. Keep from drafts. Rotate stock.
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Although we try to keep the most updated prices on our website, all prices are subject to change.
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