07 Mar Fun with Venetian Plaster: March 2, 2013
Fun with Venetian Plaster, with Sandra Duran Wilson!
Demo in Review
No, it’s not surgery at Artisans, it’s just marble dust and plaster. What a great Demo Sandra put on at Artisan, and she put the demo in a nutshell for us, and here it is. Thanks, Sandra!!
Plaster types
There are three main types of plasters: lime plaster, gypsum plaster and cement plasters
Gypsum plaster is almost pH neutral, and that makes it pretty safe to work with and less reactive with many additives and coatings; whereas, lime has high pH or alkalinity. It is more hazardous to work with and only natural mineral tints are compatible. For this reason I choose to work with gypsum plaster. Gypsum plaster is used in construction and Plaster of Paris can be poured into molds. We will deal only with gypsum plasters in this demo.
Differences within gypsum plaster: Plaster of Paris, Venetian Plaster and plaster gauze or modroc.
Plaster of Paris can be poured into molds or cast over an armature. It can also be applied like Venetian plaster, but thicker. It dries relatively fast. When Plaster of Paris is mixed with water, a chemical reaction begins that cannot be stopped. There are 3 levels: wet, set and cured. Plaster of Paris is very dense and hard once cured.
Venetian Plaster is an acrylic and gypsum product that accepts acrylic paints very well. It must be built up in thin layers. When using acrylic paints, dilute them with water so they are more readily absorbed into the plaster. You may burnish the plaster to a beautiful sheen. It is softer than Plaster of Paris and must be protected with a sealant.
Plaster Gauze or Modroc is plaster infused gauze that can be wrapped around an armature or even used on cardboard, and combined with Venetian plaster or Plaster of Paris to get some wonderful surfaces.
Substrates: Plywood or cradled wood panels. No flexible substrates will work unless adhered to a rigid surface.
Application Tools: Spatulas, trowels, color shapers, Bondo tools and old credit cards are great spreading tools.
Paints: Craft paint or watered down artist acrylics work well. I also use powdered pigments and even mix marble dust into the paints. NEVER use a thick layer of acrylic. It will not bond with the plaster and will simply peel off.
Layers: The first layer should be a thin layer, the second a texture layer that is knocked down with a trowel or other tool, and the final layer is a skim layer. I like to put a new layer of plaster over a painted and sealed plaster layer and then go back and remove some of the plaster on top.
Sealing: When I have a layer that I have painted and like, I will seal it with a watered down acrylic polymer, let dry and continue layering plaster and paint.
Removing: I use green scrubbies and sandpaper to remove layers of plaster to reveal embedded objects.
Carving: When wet, it is easy to make marks into the plaster and once dry you may still carve into it.
Embedding: You can embed thin flat objects in between layers of plaster and once dry unearth parts of them. This is lots of fun and you get some unexpected images and textures..
Transfers: Lots of ways to do transfers into plaster. Today I will demonstrate using inkjet prints.
Burnishing: Very fine grit sandpaper like 400-600 are good for burnishing. I even use a smooth stone or brown craft paper for the final burnish.
Alternative Finishes: Once the plaster is dry and cured you may seal it with a diluted acrylic finish or even wax.
IMPORTANT: Never put plaster products down the drain, this includes cleaning your tools.