How to Keep Mold From Ruining Your Paper Mache


Get a fast start on your next paper mache project or hand-made gift with Jonni’s easy downloadable patterns for masks, animal sculptures and faux trophy mounts. The patterns help you create a beautiful work of art, even if you’ve never sculpted anything before.


Today’s video is about mold, and how you can keep it from ruining your paper mache sculpture.

Here’s the short version: It’s all about the water! Mold can’t grow without water, so the way you can keep mold out of your paper mache is to:

  1. Use the fewest layers of paper and paste or the thinnest layer of paper mache clay that you can get away with. I use no more than three or four layers of paper and paste, and sometimes use less. When I use paper mache clay, I spread 1/8″ or less with a knife over the armature. (You can add more paper mache clay after the first layer dries, because it isn’t very absorbent).
  2. Put your sculpture where it can dry quickly – in front of a fan, over a furnace heating vent, or outside in the shade on a warm day. You can dry it in an oven if you need to, at around 200ΒΊ F.
  3. Never paint and seal paper mache if there’s any moisture left inside.
  4. When it is totally dry, seal it so it can’t absorb moisture from the air.
  5. Display the sculpture (or store it for next Halloween) in a dry place, the same sort of place where you’d display or store an original watercolor painting.

I have a house full of paper mache sculptures, and none of them have ever developed mold. I don’t do anything special to protect them, except for following the rules shown above.Β  Folks who live in the tropics may have to take different measures, but for the rest of us, drying the piece quickly and keeping it dry will help it last for a very long time.


Get a fast start on your next paper mache project or hand-made gift with Jonni’s easy downloadable patterns for masks, animal sculptures and faux trophy mounts. The patterns help you create a beautiful work of art, even if you’ve never sculpted anything before.


98 thoughts on “How to Keep Mold From Ruining Your Paper Mache”

  1. Hi, Jonni –
    Quite a while ago, I commented on one of your articles about a device that I’d devised to help dry pieces quickly. You enquired (not unreasonably) whether I could sketch what I’d described. So, at the risk of seeming slow to the point of sloth, I finally did it. Since this article is about mould (as it’s spelled on this side of the pond, although I’m sure it’s the same little blighter) I thought it would be pertinent to attach the image here, so that’s what I’ve done. The image is a PNG file made from a Visio sketch, so it should enlarge nicely for anyone who can’t read the text on it.
    As I said in my original comment, I tend to use only the fan heater’s airflow effect, with the heater element switched off. The amount of air moving over the piece seems to do the trick (though I’ve a feeling that humidity isn’t the problem here in NE Scotland that some of your readers might suffer).
    The idea came about because of my laziness (or forgetfulness) in not turning around a piece that was drying every couple of hours so that the air could blow on what had been the posterior, so to say. ‘Why not recycle the air flow onto the back’, I thought, thereby avoiding the need to remember things, and simultaneously halving (I hoped) the time taken to dry.
    It’s a bit ‘Heath Robinson’, perhaps, but simple enough to rig up, and I’d be interested to know if it proves to be of use to anyone else. I certainly hope so.

      • hey, what do u use in sealing ur work and how? this might be a silly question but I am having quite a hard time :)) thanks

        • I use matte acrylic varnish. You can also use the spray varnish – Krylon makes a clear coat that works, but it doesn’t smell so good in the house, so I avoid it. Acrylic varnish works well, so that’s what I almost always use.

            • I don’t usually seal the paper mache until after the paint is dry. The gesso might not stick if you use it over varnish.

  2. hi I work with marshmellows clay aka cold porcelain and the very best way to prevent mold is add mint peppermint extract it works fantastic

      • Hi jonni I still use your air clay I’m in the beginning if making the tinman when I’m done ill post him I’m teaching my grandson how to papermach again Ty for link πŸ™‚ cindy

  3. Hello Jonni

    I just love your work, and your website is a goldmine. I was just wondering,mcincerning the mold issue in papier mache, if you had ever considered using Essential Oil to help

    I am thinking of Tea Tree EO for example, that is antibiotic,my own to kill fungus etc. I am planning to do some work soon with your paste , and I will try to put a few drops in it to see if it helps. It should ! And it’s organic, not dangerous,many not clay altering…

    Maybe EO could also be used for example for those worms I have seen in one of the posts… I am not a EO specialist, but many bugs a repelled by lemongrass EO, lavender EO (remember our grand mother sheets !) etc

    By the way I have done a few years ago a goose that has hanged in my patron for years, even though in France near Paris the weather can be humid and cold. I painted it with paint spray can, and varnished it several time with marine varnish in spray can too… When I left france in March and left it to the buyers of my house, my goose was still proudly flying !!

    Here is a picture

    • Hi Sylvie. By pure coincidence I found a small bottle of tea tree oil this morning while moving stuff around in my studio, and I thought I should try it in some paper mache clay. Although I never actually have much problem with mold growing in my tub of clay, because I use it up within a day or two, and then make sure the sculpture dries quickly. I would like to know if anyone tries it in a humid climate, and to find out if it works or not.

      That’s amazing that your goose has survived so long outside. When I tried marine varnish, the sun cracked it within a month. Maybe the trick is to spray paint the item first?

  4. Hi jonni. I just had a quick question about paper maching over duct tape. Is it safe to do? Will it hold up? Thanks : )

  5. Hello Jonni
    I live in a region of Tennessee where the humidity can become almost tropical in the Summer. How much bleach would you recommend adding to the water for the PM clay? Also, if bleach is used and a varnish is used after it is dries, should there be any concern about insects with the use of flour? As a beginner working on my first papier mache project, I have been receiving advise from many different directions. I had a puppet maker friend warn me about mold/insects with flour based recipes and steered me to use a product called Zinsser Sure Grip All Purpose Adhesive. Are you familiar?
    thanks
    Michael

  6. If one were to use the flour/water paste with some vinegar and dry it according to your instructions, and the piece was painted and sealed with a mixture of 50% PVA glue & 50% water , would the piece be durable if kept indoors , and not subject to mold or insect attack ?

    I have made some miniature houses & scenery and on the off chance that maybe I might sell them one day , I would need to feel sure that the customer would get a quality product.
    The thought that moisture might be able to find its way in one day, makes me doubtful about proceeding .

    Many thanks for all the time, energy and inspiration you so generously share !!

    • Hi Jasper. If the piece is dried all the way through and then sealed, they should last at least 100 years. You can find pieces that old, and older, in antique shops. I can’t tell you, though, if the PVA glue is completely waterproof. Elmer’s doesn’t seem to be waterproof, because they make it to be easy to wash out of your clothes. If it says waterproof on the label, then it should work. I use a good quality matte acrylic varnish, myself, and I have never had a problem with mold with a piece that’s stored inside.

  7. Hi Jonni,

    Love your sculptures and I was totally inspired by them, to go back to this art form. There’s something wonderful about being able to put an idea into a 3D format isn’t there?

    I noticed a few people have asked about preventing mold. Well I found the solution and I’m happy to share it with you. When you mix up your ingredients, add 1/4 of salt to the bowl of ‘torn’ toilet paper,right at the beginning of the process and it will last for months and it seems that even if you make your layers quite thick, they dry without mold ever becoming an issue.

    I’ve been working on pieces with multiple components to each project and have never had mold develop on anything. The latest piece (shown on my blog under ‘Beautiful Things’) is a tribute to the giraffe that was known as Marius at the Danish zoo.

    Anyway, give the salt addition a try because I know you won’t be unhappy about doing so. You’ll never have to throw away an old batch of your paper clay again! And keep up the great blog and the great art! You’re a master and a master teacher.

  8. Jonni,
    I have acquired a antique dressmakers mannequin that is made out of paper/cardboard. some of the panels have completely fallen apart because of the age and probably because it has been in a moist environment. the whole thing inside and out has surface mold on it. I sprayed it down with an anti-mold product. do you think once it dries it will be ok to rebuild and strength the needed section without having to worry about further mold?
    thanks.

  9. Thank you Jonni for all that you do! I am a big fan πŸ™‚ I make sculptures with sculptamold and I am just about done with a sperm whale that will be able to hang up in a space. I am keeping the natural white of the sculptamold, not painting it, but would like to know what you would recommend to seal it with so it won’t tint it or add gloss (I’d like to retain the matte finish). Also if you have any recommendations on how I could outdoor proof it that would be SO helpful! Thank you!

    • Your whale is very nice, Elsbeth. I love the idea of having a whale ‘swimming’ in the air. A matte acrylic varnish shouldn’t affect the color or give you an unwanted shine. As for waterproofing, I’ve debated this with myself for years now, and the conclusion I keep coming to is this: The only way to waterproof paper mache is to completely encase it with some sort of plastic, like a waterproof varnish, and then re-coat it every month or so as the UV light from the sun damages and eventually destroys the plastic coating. Some people have used Marine varnish successfully, but my own experiment failed miserably. It wasn’t rain or water than killed the varnish, but the sun. A varnish with UV filters might work, if it was given another coat at least once a year. I wish I could be more optimistic, but… Since I’m skeptical by nature, maybe I’m not the right person to ask – I’d just hate for your wonderful whale to be damaged if I give you the wrong advice.

  10. Hi Jonni,
    I wanted to make a big batch to use for my summer camp class. What is the longest time you can store it? I don’t want to make a batch and have it harden.
    Thanks,
    Sherry

    • Sherry, do you mean you want to make a big batch of flour and water paste, or a big batch of the paper mache clay? I don’t recommend making the paste in large batches because wild yeast moves in very quickly and makes the paste smell bad. If you mean the paper mache clay, you can keep it indefinitely if it’s well-sealed and kept in a freezer, or for several weeks if you keep it well-sealed and in the fridge. I’ve left it out on a counter for at least a week, covered, of course, and it still works just fine. It won’t get hard until it has a chance to dry, and it can’t dry until it has access to the air.

      If you’re working with kids and you’re using the paper mache clay recipe, please use mineral oil instead of linseed oil, to avoid the chemicals.

        • I like to make small batches, and use it quickly. However, if you keep it completely covered in an air-tight container, perhaps refrigerated, it will last a week or so. If you want to make up big batches and keep them on hand, you’ll want to use the bleach in the paper soaking water, or add oil of clove to the mixture, because the biggest threats to the clay as it’s sitting in the bowl are air and mold.

          • Thanks so much! I am excited about using this recipe as commercial air dry clay is so expensive and in the schools we are always trying to save money!
            Sherry

    • Hi Sherry,

      I just noticed your comment to Jonni about ‘preserving’ your batch of paper mache, and I thought I’d jump in here and pass on what I figured out. If you add 1/4 cup of ordinary salt to her recipe, you’ll be able to keep it for months as long as it’s sealed. It works great and doesn’t affect the workability at all. Hope this helps. And have fun using it over the summer with your ‘kids’.

  11. I have just retired and having visited Venice a couple of times really want to try my hand at mask making.

    Having spent a lot of time researching on the internet – I can’t tell you how inspiring I found your videos and information links: thank you so much.

    I have been out today to source the materials you recommend and cannot wait to get started! Thank you and keep them coming!

    • I’m glad you enjoyed the videos and site, Pauline. Have fun making your masks – and be sure to let us see them when they’re done!

    • – first attempt not too bad. I learnt a lot from this one and know where to focus to improve.
      I also ordered your book from Amazon – as I know I am going to be spending a lot of time making more for the grandchildren (and their mother who works in kindergarten and is always looking for ways to inspire the little ones). Thank you for sharing what you have spent a long time learning! Kindest regards. Pauline

  12. I’ve always added a bit of bleach to my mixture, to prevent mold, & it works very well. I like the idea of using vinegar & am going to try it! The methods I use to determine if a piece (or section) is dry, is very hi-tech! If it feels cool-not done. If I can make or see a small indention, or mark, after lightly pressing with my fingernail-not done, also, I tap it it. It just sounds different when dry. I have used the oven, & setting outside in the sun to dry, but the best method I’ve found is setting up a drying area. I read about this a while back, & have worked out my own version, by converting a small closet, closing it off with a clear shower curtain (or fairly heavy plastic sheeting/drop cloth/tarp) wire shelving units, & a dehumidifier! Works wonderfully! Also a ‘safe’ area to keep pieces until ready to paint!

  13. Jonni, in Darwin they use vinegar in water to remove mold that currently is plaguing everyone. Could this be the solution to mold in papermache? I am currently not in a position to experiment, so perhaps someone else might try. Cheers.

    • Hi Beth. If Darwin is hot and humid, almost tropical, then I’m not an expert. I do know that mold and yeast hate vinegar, so that certainly does make sense, though. Also, for really humid areas, the Elmer’s Art Paste is a good substitute for the flour and water paste. The Elmer’s Art Paste doesn’t seem to get mold, although you’d still need to make sure the piece dried completely.

  14. I know you have preached about mold and mold prevention for years – that I know of; nevertheless, I really appreciate this video. And Big Bird is coming out of the bathroom, spend a little time in front of the heater, and then get sealed. Sometimes it’s not in the telling but in the hearing. You’ve done a great job here. I am always aware of mold potential, and now I can stop worrying about mold and concentrate on no water! Thanks so much. Hearing it all put together is helpful. Thanks.

    • Oh good – I was a little worried about Big Bird. Most kinds of art have a hard time in a bathroom where people take showers – but if he’s sealed and water never has a chance to sit on him, he should be fine.

      • Thank you. And Big Bird thanks you! I’m getting quite fond of him.

        I am pulling out the NO FEAR sign and am getting ready to put another and final coat of pm on Begging Dog. He’s been drying for a year now! I like that you do thin layers – that was great advice (more isn’t always better) – and it is a keen, sensible insight that every time one adds a layer of clay, one is putting water back into the project. Just a great insight. Sometimes the most obvious things are the most difficult to see.

        I took a photo of Begging Dog and wonder if you have any advice on what to do with him? I try every few months to do the texture again and never am satisfied with it. I can honestly say that doing the begging foot was the most difficult thing for me I’ve done in paper mache. (How silly is that?) ;>) I might need to buy two of your dog books whenever they come out!

        • Rex, I think you’ll be happy with the texture once it’s painted. He has a great personality, and looks like he’s about to do something, bark maybe, if he doesn’t get that treat soon. Go ahead and finish him – and then see what you think.

          • Thanks so much. I’m thinking what to do for a treat!

            By the way, I love the way your cat bosses you. Reminds me of my dog! This site is just the best.

  15. I love listening to your words of paper mache wisdom. Since I ordered both of your books, I seem to be applying several different layers to my paper mache. i.e. I covered the paper mache with the blue towels and plaster mix, then covered that with the paper clay. Is this going to result in a catastrophy????

    Please respond quickly since I’m making a giant flamingo for a production in 3 weeks!!
    Nancy

    • I do the same thing, and I haven’t had any catastrophes yet. You should be fine, as long as you give your pieces long enough to dry before you seal them.

  16. I really enjoyed this topic, sure would be a awful disappointment to have a piece ruined by mold.
    I do use my oven when I have thicker pieces to dry. I am impatient as well. I have also used a large pop corn tin that I put a light over it, it has a clip that I can use to hold it above the top and heats up well.
    I make dolls and use the clay in layers so far and I hope I never find any mold but haven’t found any.
    I hope I can add a photo of a Raggedy Ann and Andy that I made this past winter. I belong to the Maida group that Dixie S. Redmond has.

  17. Very good advice. Don’t always think about when you are in the excitement of creation. I have a large popcorn tin that I have put paper mache doll heads in and then have a light clip over it and it gets quite warm in there. I really do need to put a thermometer in there to check, but it seems to do well for me. I use the oven a lot too.
    Love you newsletter
    Artis Corwin

    • Thanks, Artis. It looks like you tried to upload a photo, and it didn’t work. Maybe it needs to be edited so it’s smaller?

      • Yes I was trying to show you a Raggedy Ann and Andy that I have made. It must be to large. The face sculpt is a thicker size so I do have to make sure it is dry.
        Thanks again
        Artis

  18. Hi Jonni
    Great advice. I also add a couple tablespoons of bleach to the water when I soak the toilet paper to make the clay.

  19. Can you speed up drying time using a hairdryer between layers? And how can you be assured its dry? I have made a few small pieces of art and I am always so impatient to see the finished result! Now I’m a bit worried I may have rushed the process. Time will tell…

    • Kim, I’m way too impatient to stand there and hold a hair dryer, so I can’t tell you how it would work. I’m sure it would if you stood there long enough, but each time you add a new layer of paper mache, like I said in the video, the dry layers will get wet again. I don’t bother to dry individual layers. Instead, I use as few layers as possible and then put the piece in front of a fan to dry. That pulls the moisture out of the piece quickly. You may need to turn it a few times to make sure it dries evenly.

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