After drying this mortar mache and styrofoam combination is already water resistant but all exterior sculptures should also get at least two heavy coats of a exterior high gloss enamel paint.
Above is a sample test piece which was hollowed out by using the acetone method. We then ran water on the shell for over an hour and no moisture entered the paper mache interior.
Its very important not to use rolled up paper, cardboard or anything else that would absorb water as the fill for these sculptures.
Weather Resistant Paper Mache
Foam can be glued to the hardiebacker with a hot glue gun. It can then easily be shaped and carved using a serrated kitchen knife.
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How to easily make outdoor weather resistant paper mache for crafting outdoor sculptures and art. Our method to make outdoor weather resistant paper mache art is unique and inexpensive. Check out our short how to videos which detail every aspect of construction and see just how easy it is. This is a great craft material for all types of backyard art.
Check out our short how to videos which detail how easy it is to create beautiful waterproof backyard sculptures.
Hardiebacker is also very useful for creating thin strong parts of any sculpture. We used it to craft the fins on this fish. During the paper mache process the hardiebacker is covered just like the foam with mortar mix and paper.
Use construction styrofoam insulation as the backing. This foam can be carved easily into almost any shape. Then apply at least two layers of the mortar paper mache mix directly to the foam. This forms a hard exterior shell.
The basic concept was to use a variety of easily available products and use them together to create waterproof outdoor sculptures. Our easy outdoor paper mache recipe starts with Flexbond mortar. This is usually used for ceramic tile work and can be found in the tile section of Home Depot.
Some exterior art needs to be hollow. For example when crafting a bird house. For these type of art projects the construction is the same but leave a hole and a couple drainage holes in the sculpture. Then before painting and in a well ventilated outdoor area pour some acetone into the piece. The acetone will melt the foam into a liquid which can then be poured out any of the holes. This will leave the hard exterior paper mache intact. If you do find any weak of thin spots just apply another layer of the mortar mache mix.
For some projects like the Sea Turtle shaped bird house a hard back board is required. For these situations use a cement board like hardiebacker. Hardiebacker will not get soft or break down even if soaked with water. Hardie backer can be cut with a variety of tools. Check out our short video on cutting the product.
Two examples of backyard art crafted from outdoor paper mache, foam and hardiebacker. Fish and Sea Turtle shown are before final paint.