Using one of my favorite materials, free cardboard, I will show you how to make an eyeball with a melon baller tool. Eyeballs can be used in many paper sculpture projects, including masks, dragons, lizards, frogs, and so on. I came up with this technique, but you could also make the eyeballs out of paper mache.
Step 1: Get a Small Piece of Cardboard
Cardboard is everywhere, just grab a piece of one ply cardboard, and you are ready to craft. Tools/materials needed: scissors, melon baller, glue, cardboard, acrylic paint/varnish.
Step 2: Trace the Outline on the Cardboard
Using the melon baller as shown, make an outline on the cardboard.
Step 3: Cut Out Circle
You don't have to be exact, just cut close to the line, but leave some excess. It can be trimmed later. To prepare for forming, wet piece of cardboard by laying on a piece of wet towel, and cover the piece completely.. You just want to soften the cardboard a bit, not have it separate!
Step 4: Force the Piece of Cardboard Into the Melon Baller
Just prior to inserting the blank into the tool, coat both sides with some white glue...not a lot, but enough to wet the surfaces. Also make short cuts on four sides so that the cardboard can flex.
Step 5: Force the Cardboard in So That It Contacts All Surfaces
To make sure you have a complete contact, use the ball on the end of a glass cutter to push the cardboard against the metal. You could also use a ball peen hammer if you have one.
Step 6: Let Dry and Then Remove
Let the glue dry for a short period of time....5 or ten minutes should suffice. Then gently remove "eyeball" from the tool.
Step 7: Glue to Backing Piece
Trim the eyeball so that it is flat on the edges and can fit the cardboard backing piece...apply a small amount of glue all around the edge as shown. Hold against the backing until set...a minute or so.
Step 8: Finish Your Eyeball
Finally, paint the eyeball in the colors of your choice. I have made the pupil resemble that of a reptile, but you could make it round and it would be a human eye. To give the eyeball a wet appearance, finish with a few coats of gloss poly urethane. Other embellishments can be added at this point, depending on the face it goes with. Note an upper and lower "eyelid" piece, plus I have cut out a lower eyelash from craft paper.