A QuiltPlan piecing guide
Snowball Corners
A square sewn on a corner, and flipped.
A small square is laid on a corner of a bigger piece, sewn across on the diagonal and pressed out, so the corner becomes a triangle of another fabric. Nothing is cut on the bias until it is sewn, so nothing stretches. Sewn on two opposite corners it makes a road, on all four a snowball, on the ends of a rectangle a boat or a sail. Unlike geese and half-square triangles, it is cut exact: the little extra comes from sewing a thread's width outside the line.
What you cut
Shown for a 6″ Snowball with 2″ triangles on all four corners. The rule for any use: the base is its finished size plus ½″, each corner square is its triangle's finished side plus ½″. A pattern gives you both numbers.
How big a corner
The same method makes all three. A Snowball keeps its corners to about a third of the side, so a flat stretch of base stays between each pair of tips and the block reads as an octagon. At half the side the tips meet in a point: that is a square in a square, or with two opposite corners a road unit like Arkansas Crossroads'.
| Snowball, finished | Base, cut 1 | Corner squares, cut 4 | Flat side, finished | Bonus triangle, trimmed to |
|---|---|---|---|---|
| 3″ | 3½″ | 1½″ | 1″ | ¾″ |
| 4″ | 4½″ | 1⅞″ | 1¼″ | 1⅛″ |
| 5″ | 5½″ | 2¼″ | 1½″ | 1½″ |
| 6″ | 6½″ | 2½″ | 2″ | 1¾″ |
| 8″ | 8½″ | 3¼″ | 2½″ | 2½″ |
| 9″ | 9½″ | 3½″ | 3″ | 2¾″ |
| 10″ | 10½″ | 3⅞″ | 3¼″ | 3⅛″ |
| 12″ | 12½″ | 4½″ | 4″ | 3¾″ |
The corner is a third of the finished side, rounded up to the eighth, plus ½″. Pressed, the unit is still the size the base was cut, and each tip lands on the seam line a quarter inch in from the edge, so the flat side finishes as charted.
Making it
1 · Mark the corner squares
On the wrong side of each corner square, draw a line from corner to corner with a fine pencil. A thick line costs size.
2 · Sew a thread outside the line
Lay a square on a corner of the base, right sides together, edges matched, the line running across the corner. Sew a thread's width on the corner side of the line, with a short stitch. On the line it always comes up short: the fold takes up a little fabric.
3 · Check it before you cut
Fold the square back over the seam. It should cover the corner and lie flush with both edges. If it falls short, sew again a thread nearer the corner. This is the only time a short corner can be fixed: once trimmed, it cannot.
4 · Trim both layers
Open it out again and trim both layers a quarter inch past the stitching, the base's corner with it. It keeps a light corner from showing a dark base through it, and keeps the corner flat where seams meet.
5 · Press it out
Set the seam, then press the triangle out toward the corner with a dry iron, lifting and lowering it rather than sliding. Steam can shrink the unit. It measures what the base was cut; trim only anything that overhangs, never the unit smaller.
6 · The next corner
Each corner is sewn, checked, trimmed and pressed before the next goes on. Where two triangles meet on one edge, as on a boat, their seams cross a quarter inch in from the raw edge.
Good to know
- Pressing. Toward the corner, so the triangle lies flat and its seam is easy to see on the back. Where four corners meet at a point, press the seams there open.
- Bonus triangles. Before trimming, sew a second line half an inch nearer the corner and cut between the two lines: the corner becomes a small half-square triangle. Trim it to ¾″ less than the corner square.
- Test one first. Sew one unit, press it and measure it before cutting the rest.
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