paste. When it is wet, it is slippery and protective. When it dries, it seems to vanish completely. The most popular mediums used are wheat paste or methylcellulose.
Starch Paste
Archival starch paste can be made from corn starch, potato starch or wheat starch. Begin by boiling water in the lower chamber of a double boiler. Add cold water to the upper chamber, measuring five times as much water as starch (volume to volume). Add all the starch to the water and use a whisk to mix the milky suspension. Continue heating and mixing the suspension for about 20 minutes. As the starch cooks, it thickens like pudding and begins to clear. When it cools, it thickens further.
Some artisans develop a ritualistic approach to preparing wheat starch. It is a food source for some creatures, so if you are not careful with the purity of the water, the percentage of starch, the temperature or other factors, microbial growth can turn starch into sugar.Allow it to ferment and the mixture can become even further contaminated. Acidic impurities are almost always harmful to the qualities of the paper. For these reasons, we prefer to use food-grade methylcellulose.
Methylcellulose is a readily available shortcut to the traditional wheat paste used by Yoshizawa and other paper artists. It is refined and pure, so the extensive aging and purification steps are unnecessary. Most paint and wallpaper shops carry dried methylcellulose. Hand papermaking, book-binding and library arts supply companies also carry methylcellulose powder.
Methylcellulose: Preparing 10 Percent Methylcellulose in Solution (by volume)
We often prepare a batch of methylcellulose by gently adding 2 ounces of methylcellulose powder (using a liquid measuring spoon), to 20 ounces of water (using a liquid measure). Sprinkle the powder slowly onto the surface of the water as you mix the water and the methylcellulose with a stirring spatula, using a brisk mixing action. Be sure to scrape down the edges to keep the expanding polymer wet. The process is faster if you use a blender although it does tend to entrap more air bubbles.
Using either method, allow the solution to sit for at least a day or two to let the lumps of polymer dissolve. Artist-quality methylcellulose seems to be a bit easier to work with than the kind sold in wallpaper stores. This mixture of viscous material has a slippery feel, just a bit lighter than honey. (Be careful not to spill this on the floor since it is extremely slippery.)
Internal size is key for some origami models. We are not too fussy about internal size any more since it is easy to add size just before wet-folding begins. It is more versatile to leave the size out until you are sure of what you need.
Applying Size to Paper
Wet-folding is often easier when the sheet is conditioned with a lubricant/size, such as methylcellulose. Before you wet the paper, cut it perfectly square. Adding moisture swells the fibers. After the model dries, the paper will return to its original dimensions.
1. Materials needed for adding surface size to paper: spray mister, methylcellulose powder, wide brush, bowl, paper.
2. Moisten the paper with water, front and back, using the finest spray setting on a spray mister. Gently spread the droplets with a light sweep of a wide, fine-bristled brush (sometimes we use a sponge or a damp cloth). Be sure not to abrade the paper when it is wet. Allow enough time for the moisture to migrate throughout the paper.
3. Brush the 10 percent methylcellulose gel onto the paper. Spread evenly from the center to the edges. The methylcellulose will penetrate the paper and adhere to the glass or plastic below.
4. Allow the preparation to dry completely. One coat is usually sufficient but allow each coat to dry if additional coats are desired.
5. Peel off the sized paper. The paper will be ready to fold when it feels like leather.
Back-Coating Two Sheets Together
When you find a nice piece of paper that is too lightweight or soft for wet-folding, back it with stiffer or stronger paper. We use methylcellulose or wheat paste to bond the two sheets back to back. Follow these steps to back-coat two sheets of paper together. This is also how we make two-color (duo) models.
1. To back-coat two sheets together, you will need the tools shown here: starch or methylcellulose powder; bowl and wet brush for the prepared paste; spray mister; wide, dry brush for smoothing; a knife (not shown). You can use a large plywood board, foam core or stiff plastic to support the back-coated sheet as it dries.
2. To begin, cut the backing paper about an inch larger than the delicate paper. Moisten each side of each sheet with a fine mist of water. Make sure they have expanded fully. Decide which side of the papers you want to show.
3. Smooth the water droplets with a wide, soft brush, working from the center to the edges. Coat the backing paper evenly with methylcellulose or paste in the same way, brushing from the center to the edges.
4. Using a wide, soft, dry brush, apply the second sheet onto the glue layer. Note the use of a wooden slat to control the upper free edge of the back paper as it is being lowered. Use a second wide, soft, dry brush to brush away any air pockets, working from the center to the edge. Be sure not to get paste on the brush!
5. After the air bubbles are brushed out, use the first paste brush to carefully apply another layer of paste to the exposed margin of the backing paper (this is showing beyond the edges of the nice paper).
6. Lay a small strip of paper across the glued margin to form a “gate” or “mouth.” This mouth provides a knife-insertion point that will speed up the removal of the dried sheet from the drying board.
7. Turn the wet composite over onto the surface of a board for drying. Use a clean, dry, wide brush (or the dry brush you previously used) to smooth out any air pockets and ensure good contact at the margins of the wet assembly.
8. After the composite is dry, carefully insert a sharp knife between the drying board and the paper at the mouth. Slide the knife around the margin to release it from the drying board.
9. The dried “duo” paper is now ready for trimming and wet-folding.
