Casting a Mask in Paper Mache
After many years of experimentation with thermoplastics, casting resins, 'non toxic' fiberglass and such, I have settled on this somewhat more traditional method of casting masks in paper mache. While it is enormously time consuming, taking me anywhere from ten to fourteen hours just to cast a large mask, it results in the lightest, strongest and most detailed mask of any method I've tried. The materials are also inexpensive and easily available, so there is no need for me to be as dependent on one or two companies or manufacturers the way I would have to be for, say, Aqua Resin or Sculpt and Coat. And because the method is so old and there are so many people who use it, there are many places to turn for information, discussion and advice.
So here is a summary of what I've learned so far. My hope is that the time I have spent learning it will be more worthwhile if I share it with others.
Materials and Equipment
The Mold and Mold Preparation
The molds I use are flexible polyurethane rubber molds with plaster mother molds. Most of my molds have two or three parts. Unfortunately I don't know of a way to make this method work with inflexible plaster molds, which I realize are more traditional for paper mache. I make sure my mold is clean and free of any residue from previous castings, but I don't use a release agent of any kind. In the method I'm going to describe, a r elease agent could actually cause lumps and divots in the cast.
Because I use a rubber mold, I allow each layer to dry as completely as possible before proceeding. Obviously a rubber mold can't pull moisture out of a cast the way a more traditional plaster mold can. If the layers build up too thickly before they have a chance to dry, moisture will become trapped in the deeper parts of the cast and will not be able to escape until the cast is pulled from the mold. This would make the cast more vulnerable to warping.
Polyfilla is a cellulose reinforced, gypsum based filler that is used primarily for patching cracks and holes in walls. It comes as a white powder in a box and is mixed with water to whatever thickness the user requires, from a thin brushable slip to a thick paste which can nearly be modeled like clay. Used as described here, it can also help make a very smooth and detailed papier mache cast. On the flip side, it will make a slightly heavier and not quite as strong of a cast as one made strictly of paper. It is necessary that mixing tools and containers be completely free of old dried Polyfilla, as it can cause the new Polyfilla mix to set up too quickly. I use disposable paper cups and bowls to mix Polyfilla for this reason. I think, but I am not sure, that gesso and/or plaster may have been used somewhat in the manner that I use Polyfilla here, and I hope to investigate this more in the future.
I'm currently using kraft paper, but I've been told many kinds of paper will work well, depending on the needs of the project at hand. Experimentation is useful. I've been told office paper can work well for an initial layer, and paper towels— preferably the blue kind that are sold in hardware stores—are good for picking up fine level of detail.
Kraft paper can come sealed or unsealed. Sealed is stronger and so is preferable. It may not be possible to tell which is which except through experimentation— sealed kraft paper will remain intact and relatively light in color if left to soak in water over a few days, while unsealed paper will turn dark and fall apart easily. Virgin paper is stronger than recycled paper, as it has longer fibers. It is possible to buy acid-free kraft paper. I prepare the paper by tearing it into dinner plate sized pieces and ripping off all the machine cut edges. The resulting feathered edge will make for a much smoother, stronger, cast. Since it has fewer machine cut edges that need to be removed, kraft paper that comes on a roll, as opposed to kraft paper that comes in a pad, is easier to use.
I currently use Weldbond, outdoor grade wood glue, and plain old Elmer's for glue. Weldbond is a kind of PVA glue on steroids, the strongest available that I know of. It supposedly can glue just about any kind of material together. I only use Weldbond for the detail coat, perhaps the cheesecloth coat, and at the very end as a sealer, as I have found it is so strong that it can make the cast almost impossible to trim and finish if the Weldbond builds up to any thickness. I use outdoor wood glue for most of the casting. In spite of any claims on the tube, I have found the glue is water resistant, not waterproof, but I figure it gives my masks a little extra protection against rain and damp. I use Elmer's to fasten down any edges I'll later have to trim on the mask. No point in using a super strong glue for parts I know I'll have to cut away! In general, I have been told most any kind of PVA glue will work for casting, with the exception of craft glue. I have been warned the bond craft glue makes may loosen over time.
The Detail Coat
The first coat is a detail coat made of Polyfilla and Weldbond. It picks up the finest level of detail from the mold, hence the name. I mix just enough water into the Polyfilla to make it workable, being sure to mix out all the lumps, then I add just enough Weldbond to make the mixture brushable. I only mix about as much as I think I will need, as the mixture will harden and become unusable in about an hour. I then paint a thin layer of this mixture into the rubber mold with a flat paintbrush. The mixture should be only slightly textured and should stick easily to vertical mold surfaces. If the mixture is too heavily textured—if it resembles beaten egg whites or the brush marks are sharply raised— it could make the application of subsequent layers more difficult than necessary and could possibly cause air pockets in the finished cast. In this case, I add a little glue. On the other hand, if the mixture does not stick to the mold and starts to run or pull away from the rubber, there is too much glue and not enough Polyfilla. If this happens, I wipe all the mixture out of the mold with a tissue, add a little more Polyfilla to the mix, and try again until the mix sticks the way it is supposed to. The thinner this initial detail coat is the better. There is no problem if the detail coat is looks spotty or streaky when it is dry, or even if it has small holes and gaps, as subsequent layers will fill these in. However, if the detail coat is too thick, it is more prone to air bubbles and other flaws, and the surface of the cast will be more prone to chipping and cracking. After I finish brushing in the mix, I clean any drips off any mold surfaces that will later join together, and I allow the detail coat to dry completely before proceeding.
The Cheesecloth Layer
The next layer is made of cheesecloth and more of the glue/Polyfilla mix. It helps the detail coat adhere to the subsequent layers of paper, making it less likely to chip and separate from the rest of the cast later. If this layer is well done, the surface of the mask will be practically flawless when it is pulled from the mold, and very fine detail, right down to tiny scratches from the original sculpture, will be reproduced. For the mix, I might use more Weldbond or perhaps a less expensive kind of PVA glue, usually outdoor wood glue, in roughly a ratio of one part Polyfilla to two parts glue. I only mix as much as I think I can use in about an hour, as the mix will set up and become unusable in this time. I cut off all machined or folded edges of the cheesecloth, and then cut the cheesecloth into smallish squares. Exactly how small is a matter for experimentation. I brush the mix (not too thick!) into the mold with the round bristle brushes, then lay the cheesecloth into it, pressing it into place with the round brushes and the stencil brushes, working up from the deepest areas. It is crucial this step is done with great care, making sure the cheesecloth is flat and tight against the mold. It is important that the pieces of cheesecloth overlap a little but do not build up to any more thickness than is necessary, as this can prevent subsequent layers of mix from penetrating all the way through to the mold and leave many pits and holes in the surface of the mask that will later need to be filled.
I overlap the cheesecloth slightly— no more than ¼" if I can help it— over all the edges of the mold, the outside edges and the seam edges alike, and press it down neatly and tightly with the help of a little Elmer's or craft glue. Oddly enough, it will not interfere with the mold assembly later on if it is done well. This will allow for neat edges when it is trimmed later, and will also help keep the layers from separating at the edges. It also provides a surface to help join the seams together when the mold is assembled later on. I then allow this layer to dry before proceeding.
The First Paper Layer
The next coat is the first layer of paper, adhered to the cheesecloth with more of the glue/Polyfilla mix. At this point I am definitely using the wood glue, not the Weldbond, to make sure the finished cast won't be so tough I can't work it later. Again I only mix as much as I think I can use in an hour. I soak the paper pieces in a bucket of water for a few minutes, wring them out thoroughly, flatten them out, and stack them on the dinner plate. They should be slightly damp, not drippy. Damp paper conforms to the shape of the mold much more easily than dry paper, but dripping wet paper is more difficult to handle, will take forever to dry and is more likely to result in a warped cast. Then I brush the glue/Polyfilla mix into the mold, tear the paper into the sizes I need, press it down tightly into the mold with the brushes and brush a little more glue mix over it. Exactly how big should I tear the paper? This is a matter of experimentation, but I have found in general it's better to err on the side of too small than too big. Small pieces fit into mold details more easily and are less likely to warp and pull out of the mold while they're drying. I overlap the paper very slightly over the outside edges and over any edges of seams I won't be able to reach when the mold is closed, and press them down neatly and tightly with the help of a little Elmer's. I don't overlap the paper over the edges of any seams I will be able to reach, I just get the paper reasonably close to the edges and then close the seams when I assemble the mold.
Subsequent Paper Layers
These are the layers that will give the mask its strength and toughness How many? Small masks need fewer layers than larger masks, masks with more detail and surface texture (hair, wrinkles, gumlines, bone and muscle structure, etc) need fewer layers than very smooth ones. The edges of masks can be vulnerable and may require extra layers as well, unless they are already reinforced by the design. For instance, the first mask above (horse) has a flat edge that needs reinforcement. The second (eye mask) has a turned-up edge that is naturally strong. In general, I use two layers for small masks and detailed areas of large masks, and up to eight to ten layers for flat edges and smooth areas of large masks. I will also use four to ten layers for long, thin projecting parts on a mask. A mask with enough layers will have only a slight amount of flex when it is demolded. If a finished mask becomes limp and rubbery and then warps when sealer is applied to it later, it needed more layers.
As I did with the first paper layer, I soak and wring out the paper, then tear it into whatever size pieces I need. As before, I brush the glue into the mold, press the paper down into it with the brushes, and then brush more glue over it. For subsequent layers I only overlap the outside edges, not the seam edges, with a little bit of paper. In my experience, outside edges need this reinforcement but seams are usually fairly sturdy, and the excess paper would only make them more difficult to clean later. I no longer use Polyfilla at this point, only the wood glue diluted with just enough water to make it brushable. The Polyfilla will have done its job at this point and hopefully given the cast a nice smooth surface, and now the paper is needed to give the cast strength.
I give the cast a day or two to dry by itself, with no air or heat applied to it. If it dries too fast, it is more likely to warp and pull out of the mold. If the cast is still damp after this time I'll put it in front of a fan on a low setting.
After the cast is dry and before the mold is assembled, I seal the inside with a mix of water and Weldbond, using only enough water to make the mix brushable. It's also possible to seal the inside of the mask after it's unmolded, but it's easier to get into all the nooks and crannies at this point.
Joining the Parts of the Mold
Here's what I do if I'm using a multipart mold. I put Weldbond on the seams anywhere where paper overlaps any hard to reach edges, and a mixture of Weldbond and Polyfilla everywhere else. I then clamp the pieces of the mold together. I brush the Polyfilla/Weldbond mix over the seams and apply two layers of paper over them everywhere I can reach. When most of the cast is relatively dry, as it should be at this time, I have found it's easier to brush the glue on the paper strips themselves in my hand instead of inside the mold. I then press them into position and apply a layer of plain diluted glue over them. I allow the cast to dry to the touch, usually overnight, and then it's time to unmold!
Cleaning the Cast
After I unmold the mask, I clean the edges and seams. I trim off whatever I can with scissors, and then do any fine cleaning with the utility knife and in tighter areas, the art knife with the carving blade. The cast will be pretty tough and sharp blades will be critical- you don't want a dull blade to jump and bury itself in your hand! I then fill in any seams and divots with Paperclay, pressing it down and smoothing it out with a damp elephant ear sponge. It is also possible to fill in any divots with the Polyfilla/Weldbond mix, or with just plain Polyfilla mixed with water, but I have had a little more trouble with the mix sinking into the divots and needing multiple applications to fill them. After the Paperclay or Polyfilla is dry, I sand it down with fine 200 grit sandpaper, and repeat the process anywhere it is necessary. When the filler is dry and I'm satisfied with the mask, I wipe any dust off with a damp paper towel and then seal the mask with a mix of Weldbond and just enough water to make the glue brushable. I have found it's a little easier to start at the highest parts of the mask and work down. I brush out any drips and runs if the glue is still wet. I leave them alone if the glue has begun to set, usually after five or ten minutes or so, as playing with them at this point will just make a bigger mess. Drips and brush marks will also level out at least a little bit by themselves when they dry. I then allow the sealed mask to dry overnight, and then it is ready to paint!
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