I bought some little plastic balls last year, circumference is 9cm. They can be covered, but covering balls is not such a plain job, not at all.
Actually, looking in internet, there's a lot of beautiful images of covered Christmas balls, the most of these are made using edgings' patterns and flowers up and down, connected with bare thread. Very pretty! Then, they are 3 tatted parts, one of these is the right length edging that fits the circumference. Simple? So-so.
http://janemactats.blogspot.it/) : "Easy Christmas Bauble" in her pattern links list.
I came to 2 different easy patterns that fit my little balls.
Thread in next picture it is the metallic gold Finca and a size 80 green cotton, wound together, they are like a size 50 thread. Those white in the picture, they are tatted with the gold metallic Finca and a size 70 white thread, that resulted in a wee bit thicker thread, but there was no need to change the stitches' count.
Rings are all 8-8, except the 3 ones that will be in the centre of the motif (bottom of the ball), these are 4-4. "SS" means switch shuttles.
#######################Pattern for the "magic triangle":
*[ R1: 8-8
R2: 8+8 (join to R1); SS
R4: 8+8 (join to R3); SS
R5: 4-4; SS
R6: 8+8 (join to R3); SS
Ch4:8+8 (join to Ch1)
R8: 8+8 (join to R7);
Ch5: 6-2-2-6 ] **
Repeat 2 times from * to **,
- joining next Ch2 to previous Ch3,
- joining next Ch4 to previous Ch1,
- and R5 joined to previous R5.
In the third repetition, R7 and R8 are joined to the very first R1. Cut and tie after the third Ch5.