Duropress plaster for press molds, 25 kg bag

Duropress plaster is a semi-hydrate plaster (CaSO4. 1/2 H2O) produced from natural gypsum mineral. Color: white

Application: This product is used in the ceramics industry for manufacturing high-hardness molds for hydraulic presses.

Specifications:
"Vicat" fluidity at a plaster: water ratio of 100: 35                   20-25 cm
Standard casting time at a plaster: water ratio of 100: 35         21 - 26 min.

Hardness at a plaster: water ratio of 100: 35:
Flexural strength 10,1 MN / m2
Compressive strength 31,5 MN / m2
Brinell hardness 106 MN / m2

Pore volume: 24,0%
Residue on a 200 µ sieve max. 0,04%

The above plaster / water ratio refers to standard formula tests. However, it may not be the same as the mixing ratio used in practice. The exact consistency must be set individually. Changing the plaster: water mixing ratio affects the product, especially the setting time and strength. The plaster / water mixing ratio used in practice is between 2,7: 1 and 2,86: 1. The recommended mixing time is 2 to 4 minutes, depending on dosage. The temperature of the plaster and the water should be as equal as possible (15 - 20 C), as their temperature has a direct effect on setting. The plaster must be spread evenly over the surface of the water and left to soak (approx. 2 minutes). The recommended mixing time depends on the mixer and the batch quantity and can be 6 to 12 minutes. Working under vacuum is recommended to avoid air inclusions. After mixing is complete, the liquid temperature must be measured. After casting, a thermometer must be attached to the mold. When the temperature has increased by 7-8 C after mixing is complete, mold ventilation can begin. The pressure can be increased by ½ bar every half minute. After reaching 5 bar, ventilate until the mold is dry, but for at least half an hour. Mold ventilation can be completed if dry areas can be detected on the surface. The mold should then dry for at least 12 hours. The use of plaster products is not recommended outdoors, in places exposed to weather or excessive humidity. When stored dry, the product can be stored for 6 months from the manufacturing date on the packaging. Moisture absorption can change the physical properties, including a decrease in strength and an increase in setting time. To protect the product, opened or torn packaging must be covered and carefully sealed.