How to Use Plaster Molds with Paper Mache

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How to use a plaster mould for paper mache clayI got an email this week from Laurence Black, who shared the result of his experiments in using paper mache in a plaster mold. (Or mould, as they spell it across the pond.)

The sculpted portrait is beautiful, and if you aren’t British you may be shocked when you see what he intends to do with it when the entire figure is done.

He also answered a question that people have asked me before – can you use petroleum jelly as a release when using paper mache clay in a plaster mold? Be sure to read all the way through to see his answer!

I asked him to write up a guest post for us to show us how it was done, and he agreed. Thanks, Laurence!

POPER MACHE. Or how to make a paper mache Pope.

©2017 Laurence Black

Jonni has kindly let me share my experiments in using PM with a plaster of Paris mould.

As you probably know, in England we burn an effigy of Guy Fawkes, a 17th century terrorist, on Nov 5th. I thought I ‘d better up my game this year as last year’s Guy was particularly unimpressive and didn’t take long to burn. Yes, those are toilet rolls…

Guy Fawkes made with toilet paper rolls
Guy Fawkes made with toilet paper rolls.

This year I wanted to make my Guy as realistic as possible while still flammable. PM is the perfect medium.

I was disappointed to discover that there are no contemporary pictures of Guy Fawkes. Historically many people burned an effigy of the Pope. Luckily the Pope at the time (1605), Paul V, has about as good an image as it is possible to have as he was painted by Caravaggio and sculpted by Bernini. Nice! He was also the Pope that gave Galileo a hard time so I don’t feel too bad about burning him.

I started off by sculpting a clay head, using a Styrofoam head as a base to save weight, time and clay. I used pictures of the Bernini sculpture as a beautiful guide.

Clay sculpture of Pope Paul V
Clay sculpture of Pope Paul V

I made a clay wall and put it around the head from side to side around the back of the ears. I then smeared the head and wall with petroleum jelly as a release agent. I then covered the front of the mould with plaster of Paris. I did several layers, each strengthened with sacking, and made it over an inch thick. I marked the edge of mould with a sharpie so that I would be able to find the seam later.

When this was completely dry (24 hours), I removed the clay wall and cleaned the area of the plaster they clay wall had been against. I then smeared petroleum jelly around the edge then made the mould for the back of the head.

I left the mould to fully cure for 3 days then used a hammer and chisels to carefully break it open along the marked seam. I managed to save the clay face but nothing else. That’s okay, I could use the face later.

The two-part plaster mould
The two-part plaster mould.

I then washed out the mould with warm water and a washing up brush to remove the remnants of clay.

Plaster moulds for paper mache cleaned and ready.
Plaster moulds for paper mache cleaned and ready.

Now it was time for my first fail. I put petroleum jelly on the back of head mould (I knew this part was experimental and didn’t want to risk the face yet). I made Jonni’s PM clay and covered the back mould fairly thinly. It dried quickly and I was amazed at just how smooth and strong it was. Unfortunately the smear of petroleum jelly didn’t work as a release agent and I could not get the bugger out. I eventually had to spent an hour chipping it out with a hammer and chisel and repair the mould. Oh well.

I now smeared petroleum jelly on both halves then used cling film. The petroleum jelly was there to get the cling film to stick. I then did traditional PM using wallpaper paste on both the moulds and the clay face as an experimental positive mould.

Paper strips and paste inside plaster moulds and over clay model.
Paper strips and paste inside plaster moulds and over clay model.

I did approx 3 layers at a time and left to dry for 24 hours before doing another 3. Eventually there were at least a dozen layers and I also incorporated a layer of cheesecloth for added strength.

In this picture the blue face is the one from the plaster mould and the newspaper face is from the clay face. The positive one is okay and would be much less bother, but doesn’t have nearly so much detail.

Paper mache results, using both positive and negative molds.
Paper mache results, using both positive and negative molds.

I joined the 2 halves together roughly by putting some duct tape strips inside and flopping half down. I then carefully lined up one side and stuck it, then closed the shell and reached inside and smoothed the other strips.

Using duct tape to line up the two halves before putting them back together.
Using duct tape to line up the two halves before putting them back together.

I then used a small amount of hot glue to firmly attach the halves. Then I PM’d over the seams until they were gone.

The two halves of Pope Paul V back together.
The two halves of paper mache Pope Paul V back together.

Next I used some ‘Polyfilla’ to smooth out some of the texture. Polyfilla is a British building product that is made from cellulose from the timber industry. This was important as this is made to be burned and I need something that both burns readily and is not toxic.

Using Polyfilla over paper mache to smooth out details.
Using Polyfilla over paper mache to smooth out details.

I sanded, smoothed, reapplied and sanded until I was happy.

Using Polyfilla over paper mache to smooth out details.
Paper mache portrait after Polyfilla has been sanded.

I then painted it with a flesh coloured acrylic.

Acrylic paint over paper mache portrait.
Acrylic paint over paper mache portrait.

I then painted the rest with artist acrylics using the Caravaggio painting as a beautiful guide.

Paper Mache Pope Paul V Finished and Ready for Guy Fawkes Day.
Paper Mache Pope Paul V Finished and Ready for Guy Fawkes Day.

He does still have the rest of his body to go, but I have until November.

While I will be a bit sorry to lose him, I do have the moulds and the method so I can make one whenever I want.

Please let me know if you have any questions on the method in case I haven’t been clear.

27 thoughts on “How to Use Plaster Molds with Paper Mache”

  1. Hi, I am a few years late in finding this page and info.
    My question is about the plaster of Paris mold.
    Once it is set up on the clay and you are removing it, you said that you washed it in warm water,…?
    How come that did not harm the mold or reactivate the plaster of Paris and make it soft and lose the image?
    Thank you,

    • Tom, I don’t know if Laurence is still watching his post for comments, so I’ll jump in and try to help. The plaster of Paris should not soften when washed with water if it has had time to fully cure. It will usually be quite hard and dry in 24 hours. There are also some special plasters, called pottery plaster, that are harder than regular plaster of Paris, so they’re excellent for molds. You can find that type of plaster at pottery shops or online. If your molds will be used often, or if there are really fine details that you’re worried about breaking, you might want to search around for a local source of pottery plaster. I hope that helps. 🙂

      • Yes it will. It’s a big solid beast of a chair so will burn well. It is also made the traditional way so has no metal parts, which is a bonus. I know it seems a shame to burn a decent chair, but there is a glut of them at the charity shops here. Hence the £6 price tag.

  2. And here’s the progress so far…
    I bought a chair from a charity shop for £6.
    I made the legs from a cardboard roll from the inside of a carpet. Carpet shops are only too pleased to give these away.
    I took all the key measurements from myself sitting in the chair. Any errors in scale are the errors that nature gave me…
    The cross piece of timber is to signify the shoulder height and width. More frame and papier mache will follow once I’ve decided how best to achieve it.

    • Hi Laurence. Your imaged didn’t come through. They need to be under 250k for my system to accept them, so maybe you could try again? If your camera has a setting for “save for email” or “save for the web,” that might help.

  3. I experimented making some hands for my Guy/Pope. The one on the right was made by wearing a rubber glove, wrapping the glove in duct tape, cutting the tape and glove off and retaping. I then put lots of layers of PM on, 3 or so at a time. When it dried I pulled the glove and tape out. I then drew around my fingers and cut out the gaps.
    In the end I dumped this design. While I was quite pleased with the result, I couldn’t escape the nagging feeling that I was somehow cheating by moulding a hand.
    To make the, uh, winning pair of hands I made a palm shape out of cardboard, then made the knuckles from balls of PM and the fingers from rolled up cardboard from a cereal box. The thumbs are a little long in this photo, but I have since changed them.

    • Laurence, I don’t think there’s any such thing as “cheating” with paper mache. Anything goes, as far as I’m concerned. But I think your hand-sculpted hands are much nicer than the reject. Have you finished the body yet? Will it be paper mache, too?

      • I am intending the bulk of the body to be papier mache. I just need to figure out how to do it, bearing in mind that it has to burn. I may have to use chicken wire but can fill it with newspaper and wood. Any ideas would be warmly welcomed. I did think of making a basketry frame, but I think that is beyond my skill level

  4. You may find that olive (or any other veg.) oil is a good release-agent. Just brush it on and use a tissue for any pooling. The best though is a silicon spray such as a furniture-polish, “Mr.Sheen” used to be great but it has stopped putting in silicon so check ingredients. All u do is spray the inside completely and then brush off with clean paint-brush (a kind of polishing action),then give another spray-coat and it is ready

  5. Hello Laurence,
    you’ve made a wonderful job! The head is amazing. It’s a pity, it’s going to be burned.
    Could you tell me which kind of Polyfilla you are using, because they are so many different kinds. And like the smooth texture you have on the head.
    Thanks a lot and … happy Guy Fawkes in November! 🙂

    • Hi, I tried normal Polyfilla powder first and it was ok, then I went for ready mixed Polyfilla fine detail and it worked much better (in that it sanded smoother). I did use a very small amount of wood filler at the end as I had some to hand and wanted to experiment. This worked best of all and is what I would recommend if you don’t need to worry about burning it and creating fumes near your family…

  6. Laurence-gosh you are a brave soul to do all that beautiful work, just to have it burned!
    I wonder if the paper mache clay would have worked if applied onto the film or cling wrap? Then maybe all those layers of newspaper could be avoided. Did you fill the finished head with anything?
    Wonderful job and a great job sculpting and painting. Thanks

    • Hi, thanks for the comment. I think the PM clay would have worked perfectly if I had used the cling wrap. I do intend to try it out when I get a chance and will post the result.

    • Hi Joni, thanks for the comment. I don’t mind, partly because it is the actual process that I enjoy more than getting to keep the end product. It’s similar to making a Christmas cake or gingerbread house I suppose.

  7. Well, I am a little disturbed, also, that there are no images of Guy Fawkes. Such a famous character ought to have a portrait somewhere! (I’ve known about Guy for over 50 years, but never saw much more than burning images.)

    I love what you have done here. The head is amazing. I hope you will show us your work when you get it finished and, perhaps, burning.

    In my defense (which I know I don’t need), we have a television show here named, “Face Off.” It is artists sculpting 3-D images that are applied to models. I have seen this show for many years, and I think I have a mental block to understanding the process. They do the sculpture in clay, like you, and then they “pour” this stuff over the sculpture. Later — all I’ve ever seen — is them breaking open the mold, cussing that something or other is “torn.” So my question may be a silly one, but where is the negative image? I see them using a power washer to “clean out the mould,” but I still don’t understand the step between the clay and the mould that is destroyed. Simple, please?

    I do love what you have done.

    • Hi Rex, thanks for the comment. I’m on holiday at the moment so am typing on my phone, but will do my best.
      The clay model is exactly as you want the finished piece. You then cover it in plaster. The plaster hardens around the model and is now ‘the negative.’
      Now, when you remove the clay model you have the exact shape in the hollows. See the picture of my empty mould. The reason for cracking the mould open is to get the clay out.
      Now when you fill the hollows with PM or resin or fiberglass etc you get a copy of the ordinal model. If you are careful you can make many copies from the one mould.

      • Rex and Lauren, when I first saw your image of the two empty halves of the mold, my eyes deceived me, and I thought it was a positive image. I guess my brain doesn’t want me to see a face going ‘in’ instead of ‘out.’ This YouTube video shows how the two pieces of the mold are made and then pulled apart so something can be cast in them.

      • Thanks, Laurence. I appreciate your simple and clear answer to my question.

        As you well know, turnips for carving “pumpkins” is going out and America’s pumpkins are taking over. Maybe next year I need to do “turnip” holidays instead of “pumpkin” holiday projects! I must have seen a Guy Fawkes burning back in 1966, but I didn’t understand it at that time. Thanks, again.

  8. Thanks for sharing every step of your experience. The fails are valuable information as well as the successes! Look forward to seeing the entire project before his ultimate demise come November.

  9. Thank you for sharing your experience and knowledge. I enjoyed it immensely. Maybe next time, we could all learn more about you.

  10. This is fantastic! Thank you for sharing your process and through the “fails” what you came to in the end. Good luck in November!


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