Keradur

The recommended plaster to water ratio is between 2.80:1 and 3.00:1.Preparation of the matrix:The preparation of the matrix is key. Air Network must be well fixed to the frame. The space between each air tubes should be constant (~ 2 cm between each). The air network should be place at ~ 2cm of the working surface of the mould.Plaster PreparationThe temperature of both the plaster and water should be as close as possible during processing, within the range 15 – 20°C, as plaster and water temperatures affect setting behaviour.Sprinkle evenly over the entire surface of the water and allow to soak for approx. 2 minutes.Depending on the intensity of the mixer and the quantity, the recommended mixing time is 6 – 12 minutes. Mixing can start since the beginning of the soaking. To avoid air entrainment, it is advisable to mix under vacuum. The temperature of the mix should be taken at the end of the mixing. The best is to control the pressure increase according the temperature increase.After pouring, a thermometer is placed in the mould. Once the temperature has increased by 6 to 8°C, the purging process can be started. The pressure should be increased by 0.5 bar from every half a minute to every minutes. After reaching 5 bar, purge until the mould is dry, for minium half an hour. The purging process can be stopped when dry areas can be seen on the surface (2 hours).The mould should be allowed to harden for at least 12 hours.