When the great Japanese master Akira Yoshizawa began visiting the West in the latter half of the twentieth century, his audiences were astounded at the organic, lifelike forms he had created. Much of the magic arose from his folding technique; rather than making every crease sharp, he incorporated soft creases, curved creases, and gentle, rounded forms. And yet, despite the softness of form, the folded figures themselves were often rigid, almost shell-like; they easily withstood the rigors of travel and retained their original form. The secret was a folding technique invented by Yoshizawa, called wet-folding.
Nowadays the term "wet-folding" is used to refer to any of a family of techniques, and the original techniques developed by Yoshizawa have been expanded upon by many artists. The common element to all members of the family of wet-folding is the application of water to the paper to soften it during the folding process. This allows the formation of both soft and sharp creases and lets you easily form curved surfaces; then when the paper dries, it retains its shape, becoming rigid and resilient. With thin papers, wet-folding allows one to compress multi-layered flaps to a much finer degree than with dry folding, allowing a much more realistic expression for legs and antennae in arthropodic subjects. I took up wet-folding over 20 years ago, and over the years, have become enthralled by its capacity for variation and expression, to the point that nowadays, nearly everything I fold for display and most of the figures on this site are wet-folded.
There are now many different papers for wet-folding and many different styles of wet-folding. While you don't need to know a lot to wet-fold, if you're planning on exploring the technique, it is helpful to understand why it works, if only to understand why some papers work and other papers don't.
The thing that enables wet-folding is sizing. Sizing is a water-soluble adhesive that is—sometimes—added to the paper pulp during its manufacture. The sizing agent acts to bond the fibers of the paper together as the paper dries, resulting in a stronger, crisper sheet. Paper manufacturers use different types and amounts of sizing in their papers, depending on the properties they're after.
For the origami folder, sizing is what makes wet-folding work. When you dampen the paper, the water dissolves the sizing, making the paper softer and more malleable; when the paper dries, the sizing bonds the paper fibers together in their new configuration, making the resulting shape permanent. The more sizing there is in the paper, the greater the contrast between foldability when wet, and rigidity when dry. Thus, wet-folding requires usage of sized papers, and the greater the amount of sizing in the paper, the more suitable that paper is for wet-folding.
So, how (short of interrogating the manufacturer) do you tell if a paper has enough sizing to make it good for wet-folding? There are a couple of answers, but the easiest is, with a little experience, you can tell by feel, particularly with thick papers. If the paper feels fairly stiff, crisp, and a little springy, then it probably has been sized. You can also experiment: dampen a sheet (by wiping with a damp cloth); if it becomes noticeably easier to manipulate, then the dampness has dissolved the sizing, and it will probably be good for wet-folding as well.
You can also just work with known good wet-folding papers. Perhaps the most readily available paper that works well for wet-folding is watercolor paper, available from many art stores in a variety of colors. I particularly like the Canson Mi-Teintes brand, which comes in a wide range of colors and has a nice surface texture. I've also found that calligraphy parchment works very well for wet-folding; its only drawback is that the range of colors is somewhat limited.
However, my favorite thick paper, by far, is Wyndstone Marble paper (in Europe, this is sold under the name Zanders Elephant Hide). This paper is very dense and smooth, and has a mottled appearance that looks like marble (hence one of its names). It becomes very malleable when damp, very rigid when dry, and is fairly resistant to getting fuzzy along folded edges (a hazard of the technique). (Interestingly, because of its elegant appearance and springiness when dry, Wyndstone Marble is a favorite paper for "dry tension folding", a completely different style in which curved surfaces are held in place by folded locks). It is available from many art stores and numerous sources on the Internet.
Whatever the paper, if it is relatively thick, you can use a similar approach for all such papers. I'll describe my own technique here; other folders have their own favored variations. I use the following tools:
When I start to fold, I dampen the cloth, then use it to wipe the surface of the paper to dampen the paper. The most important aspect of the whole process is the dampness of the paper. Too little, and the paper will be too stiff; curves will spring apart, and sharp creases will break along the fold line. On the other hand, if the paper is too damp, that's even worse; the paper will start to come apart, getting fuzzy along creases and potentially splitting at stress points. The optimum level of dampness gives the paper the feeling of leather; a bit floppy, but not soggy. If the surface is shiny, that's too wet; set the paper aside and let it dry a bit to bring it back to the right consistency.
Starting out, you must get the paper to the right stage of dampness; thereafter, you'll periodically redampen parts as they dry out. I usually find that three complete wipes gets it to the right stage to start; wipe one side, turn the paper over, wipe the other side in the opposite direction, then flip the paper over and re-wipe the first side. Of course, this depends on how damp you made the cloth to begin with. I usually start by dunking the cloth, then I wring it out enough that if I hold it loosely crumpled, it doesn't drip.
The reason for the cutting supplies in the list of materials is that it's better to cut the paper to square after you have dampened it. All of the papers I've mentioned above are machine-made papers, and all machine-made papers have a grain, which means that when wet, they swell anisotropically. If you cut a square dry and then dampen it, it will become noticeably non-square. It is a great disappointment to make your first fold along the diagonal and find that the corners no longer line up! So I always cut my paper a little larger than I need, dampen it, then quickly cut it to the proper square and begin folding.
As you fold, the paper will be constantly drying out at a rate that depends on where you live. (Here in California, it's pretty fast.) You'll have to keep an eye (or rather, a feel) on the dampness/stiffness of the paper, and re-dampen parts as they dry. Edges and corners tend to dry out faster than the middle of the paper. Once you've folded very much, some of the layers will become inaccessible to re-dampening, so I find that I pretty much have to fold a figure in one straight shot (which can necessitate 6 or 8 hours of straight folding; no coffee beforehand). If the figure won't hold its shape on its own, you can hold the paper into position while it dries, a process you can hasten by holding it in the airstream of a hair dryer. (However, this technique must be used carefully; if the figure dries nonuniformly, it is likely to warp and buckle.) I also use strips of drafting tape to hold things into position as they dry. Once the figure is fully dried, it will be quite rigid, and will hold its shape for a long time to come.
Wet-folding as I have described it requires heavily-sized, fairly thick papers. There are many beautiful papers in the world, but relatively few of them are suitable for wet-folding because they are too thin, lack sizing, or both. Furthermore, there are many origami figures that exploit the two colors on opposite sides of the paper. Traditional origami paper is colored differently on the two sides, but most art papers are not. Yoshizawa developed a folding paper that solves all three problems at once: in English-speaking countries, the technique is called back-coating. it consists of gluing two thin sheets of paper together using a water-soluble adhesive. The result is thick enough to wet-fold, can be colored differently on each side of the paper, and best of all, the adhesive material acts as the sizing agent, permitting the resulting sandwich to be wet-folded.
To backcoat two sheets of paper, you need two thin sheets, a flat surface, and a water-soluble paste; wheat starch is a common material. The first sheet is glued down to the flat surface around its edges, using a bit of the paste. The top surface is then coated with the paste, and the second sheet laid down over it. The entire sandwich is rolled to eliminate any air bubbles and to insure a good joint between the sheets; then the result is allowed to dry. (Gluing the first sheet down by its edges is a necessary step; it holds the paper flat during drying. Without this step, the paper would curl and buckle as it dries.) When the entire sandwich is dry, it is cut away from the backing, and trimmed to square. From there, one can wet-fold the material as described above.
Backcoating allows one to wet-fold a much larger variety of papers, including a huge variety of art papers from all over the world. However, it necessarily results in a sheet that is twice as thick as the paper you start with. For many origami figures, that's not a problem. But for the most complex figures—insects, spiders, crustacea, and anything with a great deal of detail—the added thickness is not tolerable. One would like to be able to apply the techniques of wet-folding to single sheets, and quite thin ones at that.
On the surface, wet-folding and thin paper would seem to be at cross purposes. After all, in wet-folding, we rely on the thickness of the paper to help the model hold its shape. Furthermore, many of the beautiful thin papers that are available have little or no sizing at all. While sizing is normally incorporated into the paper during the manufacturing process, it is also possible re-apply sizing to the sheet even after manufacture, thus allowing wet-folding and a remarkable degree of shaping.
The most common sizing agent used when resizing a sheet is a material called methylcellulose; it is also called bookbinder's paste and is a major ingredient in wallpaper paste. (In fact, as a thickener, it is an ingredient in a lot of other things too, ranging from cough syrup to fast-food milkshakes.) Paper itself is made from cellulose; Methylcellulose is cellulose that has been chemically altered to make it water-soluble. Because it is chemically inert and water soluble, it is often used in paper conservation; aging studies have shown little change over decades.
Methylcellulose, or MC, comes as a white powder that must be dissolved in water, forming a solution that can range in consistency from cough syrup (of course) to "alien slime." (In fact, Hollywood studios use the stuff by the case for exactly that purpose.) To resize a sheet of paper (or to size a sheet that was never sized to begin with), you simply paint a solution of MC over the sheet, allow it to soak in, then dry.
A small complication is that with many papers, and most thin papers, the solution of MC will soak through the paper and wick between the sheet and your backing surface, thus gluing the paper down permanently. To avoid this problem, I do my resizing on a sheet of glass (a trick I learned from origami and paper artist Michael LaFosse, more on whom in a minute). I tack down the sheet with a little MC around its edges; then paint more over the entire sheet, smoothing out any ripples and rolling out any bubbles; then let the whole thing dry. When it's dry, you can peel the entire sheet cleanly off of the glass. MC is a nice resizing agent because it soaks in completely; the top surface will look the same as it did before you started. The bottom side will have shiny spots, which comes from the polished surface of the glass. You can either fold the paper with this side inside, or if it will be exposed, wiping the paper with a barely damp cloth will take off the shininess without actually dampening the paper (which would introduce ripples).
Wet-folding with resized thin papers calls for a different folding technique. The paper itself is too thin to sustain dampening it completely before folding. Therefore, I usually fold the paper dry as far as possible; then when it comes time to shape, I selectively dampen just the part that is getting the shaping, using a fine paintbrush dipped in water. These figures can be extraordinarily delicate once dampened, so I often fold a single body part, then let it dry completely before going to the next part. Folding a figure in this fashion can take literally days until it's complete, but the results are well-worth the effort; most of the insects on this site were folded using this technique. Instead of using plain water, you can also dissolve some MC in the water used for dampening; this will add additional strength to thin features after it has soaked in and dried.
Methylcellulose is probably the most common sizing agent used in wet-folding, but there are several others. Less easily obtained is Sodium Carboxymethylcellulose, a.k.a. CMC. Chemically, CMC is more polar than MC, which makes it bind more tightly to the cellulose fibers of the paper. In layman's terms, the paper is stiffer when it dries. Even stronger than MC and CMC are the various starch-based adhesives, with wheat starch being the most common. All three are used in book conservation and have a good record of longevity. However, starch-based adhesives are attractive to vermin; no origami will survive being chewed to death by insects. Wheat flour is about 10% protein, which makes it particularly attractive to our multi-legged friends; MC and CMC are relatively inert (and I only use them in my own work). In any case, a few mothballs tipped into the storage box will keep the nasties away.
Now that you know what to do with them: what thin papers should you use? There is an enormous variety of wonderful thin papers from around the world—far too many for me to discuss. But I will mention here a few of my favorites.
Many of the good thin papers for folding are handmade, and most of them are made from plant fibers other than wood pulp. In general, you should avoid papers made from wood pulp (which takes in the vast majority of the paper made in the world). Wood pulp for paper is made by grinding up wood chips by one of two processes. Thermo-mechanical processing (TMP) primarily uses heat, steam, and grinding to break the chips down into individual fibers; chemical pulp uses acid and other harsh chemistry to break down the cellulose and lignins (and incidentally, gives paper mills their distinctive, and long-ranging, smell). TMP must grind the chips into small bits for the steam to do its work, and so, despite its (relative) environmental friendliness, the paper fibers are shorter and weaker than those in chemical pulp. Most commercial paper is made of a blend of the two, with lower grades (like newsprint) having a higher proportion of the short-fibered TMP pulp.
Short fibers are bad for folding, and they are really bad for thin papers for folding. Thin papers usually mean complex figures, and complex figures usually mean the paper will be put under stress, and stressed short-fiber paper tends to split, leading to even more-stressed origami artists. Fortunately, many of the most interesting art papers are not made from wood pulp; instead, they are made from various plant fibers. Owing to either the nature of the plant, or the relatively more benign process used to extract the fibers from the plant, these types of pulp can have very long fibers, giving paper that is thin, uniform, and strong. As an added bonus, pulps provided for artisan papers are usually carefully pH-balanced and contain none of the lignins common in wood-pulp papers (which turn yellow fairly quickly). A pH-balanced paper (so-called "acid free") will not degrade over time; in fact, artifacts made from handmade paper have been found in Japan that are over 1000 years old!
Occasionally, you will find that paper has been labeled by the pulp from which it is made. Common plant source fibers include mulberry, which is the traditional material for most Japanese handmade paper. The Japanese name for mulberry is kozo, and some of the best papers in the world are made from it in Japan. A similar plant fiber is gampi, which produces another high-quality paper. Korea also has a tradition of handmade paper, using kozo fiber. They don't call it that, of course; the Korean word for such handmade paper is hanji; I use a great deal of hanji in my own folding, and you can find various sources for it on the web. Other papers made from mulberry include unryu; there are many varieties, so you're best off to find a store where you can browse the paper directly and examine its thickness, crispness, and other feel.
One of the most interesting plant fiber papers for origami comes from Nepal; the plant, and the paper, is called lokta. There are numerous sources for lokta paper on the web, and I've also found it in the occasional art store. I don't know if it's due to the fiber, or the specific process they use in Nepal, but lokta sheets often have a subtle mottling to them that is just distinct enough to be interesting but not so bold as to be distracting. The thickness of the sheet is highly variable. In fact, the thickness can vary substantially across a single sheet. This makes it a bit of a challenge to fold, especially if the thick part of the sheet shows up in a part of the figure that should be thin, but a little advance planning can avoid that. For some models, it's just the thing: the Bull Moose on the home page of this site was folded from lokta. One caution: at least some of the lokta I've seen is dyed in garish colors that are almost certainly unstable dyes; this calls into question the color stability of the entire line.
I have, naturally, saved the best for last. Without question, the best thin paper for origami in the entire world comes from Haverhill, Massachusetts, from the Origamido Studio, home base of Michael LaFosse. Michael is well-known as one of the world's great origami masters. But he is also a master paper-maker, and over the years he along with his partner Richard Alexander has developed recipes and techniques for making paper for origami that is thin, strong, crisp, takes a crease, and isn't overly weakened by folding; in short, it's as close to perfection as I've ever seen. Michael primarily makes paper for his own works, but a couple of times a year, he makes paper available for sale to the rest of us. It's only in stock occasionally—and when it is, the world's origami artists fairly quickly buy him out—but if you're serious about folding complex figures, hie yourself over to Origamido, and try folding the very best. All the papers are pH-balanced. Even more important, the colors come from mineral pigments rather than (potentially unstable) dyes. This paper will last a lifetime.
That's a rapid tour through the range of papers for artistic origami. Not a complete tour, by any means, but a sampling of what's available and what to do with it. But it's possible to fold many things other than paper, and it's possible to fold things considerably outside the breadbox-size range of most artistic origami. In the next section, I'll touch on a few other folding media used for special purposes.