Whether you’re making your own lawn sculptures or simply want to make a model that can withstand the elements, it’s important to remember that waterproofing paper mache has been called a “holy grail” of paper mache artists. It isn’t impossible, by any means, but it can be difficult if you try traditional methods.
The three key things you need to make a paper mache sculpture waterproof are waterproof glue, a thin set mortar-mache and exterior house paint.
Paper mache, by nature, is made of paper and paste, neither one of these things hold up against rain very well. If you want your paper mache to do something non-traditional, you’ll need to make it out of non-traditional materials.
This isn’t to say you can’t branch out when making your sculptures. Some artists use craft foam on the inside, or shop towels, or anything that gets their sculpture to hold its shape.
What is important is to make a protective shell that will keep out moisture from the rain, snow, or flooding. Be mindful of your climate, as a sculpture made in Arizona’s desert heat will hold up against moisture better than one made in Georgia.
Make Your Base Sculpture
Before adding in any of your bonding materials, make your sculpture’s frame and shape. You can do this like any paper mache project, with newspapers and cardboard before adding in your paste and bonds.
Having a solid foundation will make it easier to waterproof your sculpture, and naturally, you want it to look good!
There is a suggestion of using sculpting foam for your sculpture and coating it with the water proof mixture here, and the crafter suggests using acetone to melt the foam out afterward as to mitigate the moisture that may accrue inside, but this is optional and not always suggested as acetone can be dangerous.
Layer of Wood Glue and Water
After the first layer has dried, you can move on to your second.
Use a waterproof wood glue and mix it with water for your paste. It can be a one-to-one mixture, but as it dries it will get thicker, so add water to keep it at your desired paste thickness.
One way to apply this mixture to your newspaper strips is to coat them in the mixture with a brush and place them strategically on your sculpture. You can guarantee a good coating this way, which is essential.
Another option is to apply your paste directly to your sculpture, apply your strips, and then add another dollop of the mix to saturate your newspaper. This method could be quicker for you, and you would be adding more of the mixture to your sculpture.
Just be sure that your waterproof mix has coated your sculpture with your newspaper mache. This will make sure no water from rain or snow will get to the sculpture underneath.
Double-check the bottom of your sculpture as well, and all the creases or where the mache bends. These will be the places that water is more likely to seep into or moisture is more likely to get trapped. Letting your sculpture dry completely between layers can eliminate the threat of trapped moisture as well.
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Layer of Waterproof Glue and Exterior Latex Paint
Next, mix a layer of your waterproof glue and exterior paint. The color can be whatever you choose, but it’s vital that you coat the entire sculpture with this mixture just as you did the last. Try not to add too many layers of additional paper until the next step.
This will seal the mix beneath it and prime the sculpture for the next layer of mache.
KILZ Exterior Paint
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Layer of Thin-set Mortar Mache
Make a layer of paper mache like the first one, only instead of wood glue and water, use a readily available thin-set mortar instead of glue or paste. A good mixture has been using 2 parts mortar to one part water. Add more water as it dries to ensure you’ve got the right consistency.
Dip your strips of newspaper in the thin-set mortar like you would with any other paste, and shape your sculpture with them. You can use either of the two methods as the first layer, whichever works better for you.
After you’re finished and this layer dries, coat the sculpture with one more layer of the thin-set mortar for maximum protection. Don’t add anymore paper from this step on, make sure it’s the shape you want it to be in.
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Your final layer will be your layer of exterior house paint. It can be whatever colors you want or need it to be, as long as it is the kind that is meant to be used outside. This will make it more durable against the elements.
An optional final layer is a coating of polyurethane to seal your paint, but if you want to maintain the integrity of your coloring, this can only be applied for one coat. Multiple coats of polyurethane can outshine the color of your sculpture.
Along with the right materials, be sure to put your sculpture somewhere it’s least likely to get into prolonged contact with the rain or sun. A waterproofed sculpture isn’t as resistant to being sun-scorched as it is to the rain, and sun-damage can destroy all your hard work. Even houses get leaks, so protect your sculpture by putting in the right place (and not in the path of your storm drains).
Making your paper sculptures waterproof and weather resistant is possible, you just need to use the right materials to protect your creations from the rain and snow.
Using a waterproof wood glue, thin-set mortar, and exterior house paint have done wonders for keeping sculptures and other paper mache objects around for the long haul outside.