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We’ve have been using this plaster based replacement powder over the last two years. The recipe is simpler and more available than our previous plaster recipe. It was developed over a period of about one year. It has ok damp strength, good green strength, and is quite strong after baking in the convection oven (with a temperature between warm and defrost). When finished, one might infiltrate with CA glue, or thin epoxy, or wax/paraffin.
DAP Plaster of Paris 1000 units
Powdered Sugar 250 units
Maltodextrin 250 units
If you can’t find Maltodextrin, then use Benefiber (it is no longer maltodextrin but rather a wheat dextrin). Also, you might try experimenting with replacing the sugar 1:1 with Polyvinyl Alcohol (PVA/PVoH). PVA is much more expensive than powdered sugar but there are some advantages.
PVA is a really vast array of products and modifications of base product. Contact a technical rep for a vendor near you to discuss your application.
There are a fair number of different kinds of plaster of paris – common plaster of paris, #1 Pottery Plaster, Drystone Plaster, Duramold Plaster, GardenCast Plaster, Hydrocal Plaster, Ultracal Plaster, and various Dental Plasters. Each plaster has different properties and each requires experimentation. We have been using DAP Plaster of Paris (especially because it is readily available for a reasonable cost).