Waterproof “Paper Mache” Technique

Note: Dan Berg, the creator of this video, suggests using acetone to make a foam sculpture hollow. Read the comments below to see why using acetone for anything is very dangerous, and should only be used by people who are very aware of everything that can go wrong. I personally recommend not using it at all!

If you’ve been watching my blog for any length of time, you know one of the most common questions we ask is “how can I make my paper mache sculptures waterproof?”

I’ve experimented with several different methods and products for waterproofing paper mache, and all my experiments have been miserable failures. I know people say that marine varnish will work, but it didn’t work for me.

That’s why I was so excited when I got an email from a reader yesterday with a link to the video on this post. It was made by Dan Berg, of DIYeasycrafts.com. I haven’t tried this yet, but I watched the whole thing and I can’t find any reason why it wouldn’t work. Here’s why:

  1. The inside of the sculpture is foam, not crumpled paper or any other organic material. That means that even if there’s a pinhole in the outside ‘skin,’ water leaking inside won’t cause any damage.
  2. The ‘paper mache’ uses mortar mix with the paper strips, instead of paste. Ants, crickets, and mice should have no interest in chewing holes in the skin of the sculpture. (Do wear gloves. The mortar will dry out your skin.)
  3. The mortar mix is covered with exterior paint.
  4. The fellow who made the video actually did some tests, and he proved that the mortar mache is waterproof. It even holds its shape when he removes the foam and leaves the sculpture completely hollow.
  5. The mortar mix is much cheaper than the commercial foam coatings that I’ve seen. The cost of the coatings is why I haven’t tried sculpting with foam until now.

The man in the video is using a particular brand of mortar, called Flexbond. You can find it at a Home Depot near you. And it looks like he’s using the blue rigid foam insulation sheets, which you can also find at a building supply store. The sheets would need to be glued together to make a piece big enough for a sculpture, and you’ll need special glue for that. The guy at the store should point you in the right direction.

You can use a bread knife to cut foam, but it leaves little nubbins of foam all over everything, and static causes the pieces to stick to your clothes, and they end up all over the house. I think I’ll grab a foam cutting knife before I start my project, to avoid some of the mess.

I really hope to try this soon. The hard part will be sculpting the foam. I like sculpting by addition, adding bits of clay or paper until I like what I see. Foam requires “subtraction,” taking away the excess material until you get the shape you want, like stone carvers do. Maybe if you take off more than you wanted to, you could repair the boo-boo with expanding foam.

I found some interesting sculpted foam projects out on Pinterest. If you try this, please let us know how your project turned out.

54 thoughts on “Waterproof “Paper Mache” Technique”

  1. Interesting technique, and thanks for all your tips on paper maché!

    As others have mentioned, use good ventilation and an organic vapor mask, not a dust mask, when working with acetone. You can find activated charcoal masks, reusable and disposable, and they are the best value if you use acetone occasionally. They work for other types of paint fumes also. If you are making several small sculptures, you can pour the excess from the first into the second, to get started melting that foam and use all the acetone’s chemical power.

    I’d suggest oil based enamel for outdoor projects. It isn’t as easy to clean up as latex paint, but it hardens better and doesn’t chalk— outdoor paints dust off their outer layer to keep the paint looking fresh (called chalking), and the residue can stain whatever is in the path of the water flow. You sometimes see this on houses with painted siding above a brick wall. Paints aren’t generally labeled as oil based any more, but ones that are marketed as enamel for metal are actually oil based. Top of the line would be One Shot signpainters enamel, which is beastly expensive but has colors designed to blend well without graying out.

    Finally, be careful when cutting foam with a hot knife! The smoke contains cyanide gas and is highly toxic. Make sure you have plenty of ventilation, you don’t want it staying in the house.

  2. Hi Jonni! I’m an art artist living in France, and I used the recipe in this video make a large waterproof clam sculpture for an outdoor sculpture park in the village of Liffré. I had to tweak the recipe a bit, since we don’t have all the same brands available at the hardware store. I used polysterene sheets, glued together with polysterene glue around a metal structure that I had treated with an anti-rust spray. The glue didn’t actually work that well, as there wasn’t enough air circulating between the sheets, and I ended up having to stick the interior of the sculpture back together using metal rods and expanding insulation foam. After that I did about 6 or 7 layers of paper maché using strips of newspaper and a flex mortar to which I added a resin product for mortar (used for building things like pools) and a powder used to make mortar water-resistant. Then I used two coats waterproof outdoor housing paint (white, which I was able to tint using acrylic paint tints) and finished it off with two layers of clear sealant. The piece has been installed outdoors since the middle of September and I am happy to report that so far it has withstood the windy, rainy, humid climate of Brittany very well! I’ll post back with updates on it after a few months to see how it holds up in the long run. Anyway, thank you so much for your post! Here’s a picture of Le Clam installed at Hubhug Sculpture project (it’s the blue cartoony thing with eyes and the big smile 🙂 )

  3. Thanks so much for the info! I’ve been pondering water proof paper mache for some time. I don’t mean to offend you, please understand I have only good intentions here. Please don’t let the water just run in your sink. The thoughts of it running for the two hour test makes me sad. . Our water is precious. Please use it wisely. Thank you for your time.

  4. I have been working with paper mache over the years. THE BEST product that has maintained the integrity of my outdoor seasonal pieces is that rubber coating spray for the outside(it’s paintable) and in the interior for added strength, I use a spray foam. It keeps thing light, but solid. Previously, I had used varnish, sprays, etc. Nothing waterproofed as good as rubber coating. If you check out my website, you’ll see what fails and what I nailed over the years. Search keywords like Jack Skellington, Sleepy Hollow Pumpkin.

    • Very true. I think the container is covered with warnings – if not, it should be. Some nail polish removers are made with acetone, and I hope people who use that product are careful, too.

      • A friend just had all the hair burned off of his face and arms from cleaning a couple of things in his kitchen with Acetone. No open flames around, it was just static electricity from a dry miracle fiber wash cloth he was using to wipe down with. I would never EVER use Acetone for anything. It’s extremely dangerous !

        • Good lord! I knew there was a reason to stay away from that stuff! I just added a huge warning notice right below the video. Thanks for letting us know. I hope your friend recovered from his mishap!

  5. I love the pink styrofoam insulation sheeting. I have used it in three dimensional paintings that I’ve done where I cut the foam with a very sharp utility knife blade and fit pieces together to create the images I want. I’ve been doing this for many years and love it. I sand the sharp angular edges with a fine sandpaper and yes the foam actually has a grain of sorts, and will come off in chunks if I go the wrong way. I paint it with a white paint and then add color and details in acrylic paint. I’m anxious to try it as the “armature” to outdoor paper mache sculpture. Thanks for the inspiration

  6. Rather than coating the cement with exterior paint, I wonder if it would work to make your own I step coloured coating compound by mixing the cement with paint instead of water. I’m sipper I saw that on a Halloween blog somewhere.

    • You might be thinking of the Monster Mud, which is used a lot in Halloween displays. It’s a mixture of 5 gallons of pre-mixed drywall joint compound and one gallon of latex paint. Do a google search for Monster Mud, and you’ll see a lot of examples – but I don’t think I’ve ever seen them use it with paper. They usually dip fabric into the goo, and drape it over their forms. It could work layered, though – it would be worth a try.

  7. Have you ever heard of or used Paverpol? I saw it mentioned in an off hand way when I was searching for a durable product that could add strength and weatherproofing to paper and fabric. I just found out dickblick carries the entire line and Paverpol has several videos explaining the versatility of their products and how to use them. It is a non toxic line of products used for sculpting with fabric and paper among other things. There is paverplast powder that is mixed with a textile hardener but either can be used by themselves.It is waterproof and can be used for outdoor projects. They have a few other products that I have not done research on but I am chomping at the bit to play with the textile hardener and the powder. I’m currently working on an experimental method of paper and fabric mache and sculpting a halloween witch – (not a theme I work with- just a lack of any other idea at the moment-) that I would like to hang outside and how I came across this thread. I appreciate artists and designers that freely and openly exchange information and hearing about the varied experiments and results that others have tried- or failed! Thank you for that.

    • I have not tried it, but if Dan Reeder says it will work, I’m sure he’s right. Maybe I’ll give it a try one of these days. If you try it, please let us know how it worked out.

  8. Regarding the plastic foam/acetone slurry from melting out the foam board armature…we have used this mixture to seal different items that were destined to be left outdoors. The slurry was either poured or brushed onto the item being sealed. When the solvent has evaporated the plastic hardened. Worked very well.

  9. I have been working over the winter to create two (2) life size pieces for 2016 Christmas, a snowman with twinkling lights around the hat band, and a five foot Goofy skiing (with arm and head motion. The armature(s) were made out of Chicken Wire, foam board and plywood (still very very light). I covered the armature with Masking Tape and several coats of Paper Mache. When the weather breaks (Midwest Weather) I am going to cover them with “Polyester Resin and Chopped Fiber Glass” (Outdoors). I will then spray the final product with “Gelcoat” before applying primer and painting. “Should be” water proof and “Strong” for winter display. Will send photo(s0 if I ever finish and succeed.

  10. Hi! I have a question I want to make a garden angel. I have a chicken wire base which I’m thinking about making the above water base paper mache then I would like her to look like she has a ribbon shirt so I was wondering if duck tape would stick to this? There are so many pretty duck tape I thought it would look like ribbon. The duck tape won’t stick directly to the chicken wire. Then I’m thinking for her hair to use yarn and ribbon then clear coat them with some
    like maybe crylon? Unless you have any suggestions? I’ve never done anything like this before

  11. Dan, what are the mixing instructions for the FlexBond as you use it in these projects? I am thinking you might add more water than the instructions on the package call for because it seems like the Flexbond mix would be thicker than what you show in the video. It looks to be more like a runny paste rather than a thick thinset that could be used with a trowel.


  12. I work with cement over polystyrene. I join the pieces together with long nails or PVA glue. It only needs to hold together long enough for the cement to set. If I make a mistake I just glue or nail a new bit on! The nails do need to be made of galvanised steel though so they don’t rust or cause a reaction with the cement. Although it is very messy I like the polystyrene that has a sort of fluffy texture. I can use my thunbs to change its shape rather like working with clay. The polystyrene used to pack large kitchen appliances tends to be very rigid and hard to cut and impossible to break up by rubbing with fingers. I scan skips and bins when I am out in search of free polystyrene or buy the insulation sheets if I have to.

  13. That looks like a fun technique to try. Ibet you could make some really stunning ‘outdoor’sculptures. I wonder whether it would be safer to cover them with a plastic sheet in the winter. It gets really wet here in the UK.

    • Thanks, Dan! And thanks for giving us your name – I didn’t have it when I posted your video. I’ll add it to the post, so you get full credit. It’s still a little cold for outdoor projects here in Minnesota, but I’m going to try your method as soon as it warms up.

    • This is a great idea! Your water running for 2 hours test certainly gives me confidence! I’m really curious how it will hold up over a few cold winters. The flexbond says it has crack-prevention so it seems like a good bet. Thank you for sharing your process Dan.

        • Good to know, Dan. By the way, I just watched your video again, and I’m still amazed by how thin the mortar ‘skin’ is on your sculptures. I can’t wait to try your method.

            • I have not tried Dan Reeder’s idea of using outdoor wood glue for paste, and dipping the final fabric skin in wood glue. He does have a dragon hanging in a tree outside his house (in Seattle) and he claims it’s holding up well. I don’t know how well it would hold up in our Minnesota winters. I did try concrete water-proofer, and it failed miserably.

              I need to make something for outdoors – a pet memorial stone, unfortunately – but I’ll be using concrete. I have given up on using paper mache outside except for very short holiday displays. If you try that product, please let us know if it works.

            • I’ve seen some of those. Some websites claim the material doesn’t hold up well when used to make houses, but it probably wouldn’t affect smaller sculptures. I’d also like to try using hemp hurds with concrete. It’s supposed to make the concrete much stronger. I have ordered some ShapeCrete from Home Depot, and it should be here next week. I’ll make something with it, and post a video.

          • hemp hurds — I had to look that up, never heard of it. Thanks for telling me about it. I will read up on it and hempcrete. Looking forward to seeing your projects made with hemp and ShapeCrete. Please add me to your enewsletter list. Thanks!

            • Joni, as a followup on the ShapeCrete – I ordered some and just now finished playing with a small sample. I was concerned because they say it can be used like clay, but none of their videos show them using it the way a clay sculptor would use clay. They were using it the way my dad uses concrete. Not a bad thing, except that a bag of 50# ready-mix concrete costs about 7 bucks. So, I tried a small portrait with the ShapeCrete over a plaster-cloth skull mold, and here’s what I found:

              You need far less water than the instructions call for. You have less than 15 minutes to work, not the 30 to 60 minutes on the label. And it works just like concrete – except that it has sand instead of gravel, so it might work better in a detailed mold. It also has short pieces of fiberglass that might help reduce cracking. I was not able to get any fine details, my little man’s nose slumped (I used too much water) and it got hard before I could add the eyes, even though I was working really fast. I don’t think I got my $30 worth, and it definitely does not work like clay.

              The formula I used for my garden face (see it here, with a link to the formula) was much easier to use, it’s finer, and it can actually be shaped into fine details. There’s a reason why all the videos on the ShapeCrete site show people making slabs, or using the product in a mold. I was disappointed, to say the least.

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