Mixing glue and water results in thinned glue, which has many applications, such as a sealant or for papier-mâché. Water will also recover Elmer's glue that has thickened over time. Think about the glue's thickness in terms of the ratio of water to glue. Each ratio has different properties and will work better for different projects.
Just Thinned a Little
Mix four parts glue into one part water. This is about the least amount of water that you can mix into Elmer's glue to see an effect. It retains its sticky properties and will still have body. When the glue dries, it is strong. This application will suit model-building projects such as rockets, cars, sailing ships and dollhouses. It is also ideal for scrapbooking, montages and mounting photos to mattes. One coat will work well when glazing things like windows as well; the finish will be smooth and satin.
Thin Enough to Paint With
Mix three parts glue into one part water. This is about the furthest you can thin Elmer's glue down to still have a hard surface when dry. Many coats will build up strength. Use this ratio to stretch the glue for papier-mâché projects like statues, masks and costumes. In addition, use it to coat paper crafts such as origami that you want to harden and preserve.
Mix two parts glue to one part water. The two-to-one ratio is thin yet workable on most surfaces. When it dries, it will be brittle and therefore has less permanence. Use many layers for additional strength. This ratio is perfect for decoupage and crafting projects involving plastic, linoleum and glass. The dried glue will be elastic.
Mix one part glue into one part water. This ratio has the best flow properties. It is easy to measure and it retains all of its bonding properties. It is too watery for gluing hard surfaces, but can be used in ultra-thin ceramic-like glazes. It is also ideal for projects that only need a temporary adhesive, such as decorating a bedroom wall with stars or animal cut-outs. By heating the glue up with a hair dryer, the adhered item can be easily removed.