Modelling plaster, strong

Items cast out of gypsum absorb water and are therefore not suitable for constant water exposure, e.g. as flower vases or bird watering holes. A clear varnish (varnish spray, matt varnish or food-safe varnish) provides effective surface protection and makes it water-repellent. However, 100% waterproofing cannot be guaranteed, as these varnishes are applied by hand and cannot be baked in oven.

Processing temperature:

Cold powder or cold water extends the processing and curing time. This could impede the curing process, resulting possibly in a lower final strength. In order to avoid this, we recommend leaving the cold powder to stand overnight at ambient temperature (20°C). The optimum processing temperature for powder and water is between 18°C and 25°C.

Mixing procedure and casting:

1 part of water to 2,5 parts of gypsum.

Air bubbles may occur when stirring gypsum. To minimise their formation, we recommend pouring the ready-to-cast gypsum slowly into the mould (e.g. over the concave side of the spoon) so that from the outset only a light layer free of air bubbles emerges on the surface. The rest of gypsum can then be quickly poured in. After pouring in, tap gently on the mould to dislodge any air bubbles.

Please allow the casting compound to dry thoroyghly in the mould and also allow the cast object to harden fully in open air after demoulding. If the demoulded items remain slightly wet, they can discolour.

Tips for a neat finish of gypsum

• After drying, rub off any excess powder with a dry cloth.
• The non-smooth rear side of the cast item is more porous and has edges with minimal burrs. This issue can be resolved by sanding the rough surface with fine sandpaper.
• Please take into account that sanding hardened gypsum items - regardless of colour - causes so-called sanding dust, which can be wiped using a moist cloth and washing-up liquid.
• That's how it becomes colourful: put the pigment powder into the liquid casting compound or paint over while it has dried out
• For heavily structured shapes, bring some casting compound into the hollows by using a brush, so that air bubbles do not form, then fill it out with the rest of the mixture