The addition of Plaster Polymer to plaster adds another dimension to the quality of  plaster casts – it makes the casts tougher, harder and unlike normal plaster casts, not as brittle. Adding Plaster Polymer is like adding a liquid plastic into plaster mixes. Whereas plasters tend to be brittle, however hard, the addition of polymer changes all this and opens up a wide range of new applications.
We recommend it is only used with alpha plasters (harder, high quality plasters), like Crystacal R Plaster. It will work with Beta plasters, like Fine Casting, however is not so effective.
The mix ratio of Plaster to Polymer will depend on the nature of the casting being carried out. For the best result use the Polymer neat and a mix ratio of 2.5:1 parts Plaster to Polymer by weight (so 2.5kg Plaster to 1kg Polymer).
However if using the Polymer neat is too expensive, we recommend a minimum of 10% addition of Polymer by weight to the gauging water before adding the Plaster. Higher concentration should be used for the best results – mechanised mixing is recommended for this. For best results use neat i.e., use Polymer instead of water.
The addition of this Polymer also means that pigments are dispersed a lot better, Jesmonite Pigments work very well, as will any water or acrylic base paint or pigment.
With a higher concentrated mix of Polymer to Plaster i.e., 2 parts Plaster to 1 part Polymer, you can also add fillers, such as stone dust and lightweight filler powders. These can be added at between 70 and 100%.