How to make a picnic blanket

1. Materials & tools

Materials (one blanket, for 4 people)

• Outer fabric (canvas, heavy cotton or duck) — about 150 cm × 110 cm
• Backing fabric (water-resistant or laminated) — the same amount
• Hook-and-loop tape, 2.5 cm wide — 8 cm
• Optional: lightweight quilt batting for the middle

Tools

• Sewing machine (or needle and thread)
• Fabric marker or pencil
• Ruler and scissors
• Iron
• Pins or clips

2. Make the pattern (auto-generated in Katagami)

With the Katagami pattern tool, you just enter the finished size and it drafts a seam-allowance-included pattern, tiled to print at actual size on Letter or A4.

1. Open the tool
   Open the pattern tool and choose “Home” → “Picnic blanket” from the tabs at the top.
2. Enter the size
   Enter the finished width, depth, corner radius and the strap length. Presets cover 2 people, 4 people and family size.
3. Set the seam allowance
   Use the slider at the bottom (beginners: 1.0–1.5 cm / about 3/8–5/8 in).
4. Print
   Press “Print (actual size)”, then in the print dialog set Scale = 100% and turn “Fit to page” OFF. Check the 50 mm calibration box on the first guide sheet with a ruler.

3. Cutting the fabric

1. Choose the size
   About 120 cm wide seats two adults, about 140 cm seats four. Allow for where the bags go too — slightly larger is more comfortable.
2. Check the cut sizes
   It is large, so rather than printing the pattern, mark the measurements from the guide sheet straight onto the fabric. For the rounded corners, trace round a plate or a bowl.
3. Cut the pieces
   Cut 1 outer and 1 backing. If the fabric is not wide enough, join two widths and offset the seam so it does not land in the middle.
4. Handling laminated fabric
   Pins leave permanent holes in laminated fabric. Use clips. It cannot be pressed either.

4. Sewing

4-1. Make the strap

1. Fold the strap in four (both edges to the center, then in half) and press.
2. Topstitch 3 mm from both long edges.
3. Sew the loop half of the hook-and-loop tape to one end on the front, and the hook half to the other end on the back.

4-2. Sew with the strap caught in

1. Spread the outer right side up and baste the raw end of the strap halfway along one side, pointing inwards — where it comes round to when the blanket is rolled.
2. Lay the backing on top, right sides together. With laminated fabric, hold it with clips.
3. Sew all the way round, leaving a 25 cm opening. On something this big, leave a generous opening.

4-3. How to sew laminated fabric

1. If the laminated face sticks to the presser foot, lay tracing paper over it, sew through both and tear the paper away afterwards.
2. A Teflon foot is the reliable answer. Failing that, a strip of tape on the sole of an ordinary foot helps.
3. The piece is large, so set a table in front of and to the left of the machine to support it. Unsupported, the weight drags the stitching off line.

4-4. Turn and finish

1. Clip the seam allowance around the rounded corners every 1 cm.
2. Turn right side out through the opening and shape the corners.
3. Fold the opening edges in and topstitch 5 mm from the edge all the way round.
4. A grid of quilting through the middle stops the two layers shifting. The bigger the blanket, the more it matters.

✏️ Do not put pins through a laminated or coated backing. The holes never close, and water comes through them. Use clips, or keep pins strictly inside the seam allowance. Observe that one rule and the rest is just a large rectangle.

5. Tips & variations

• Coat the back only: a water-resistant face on top makes it slippery to sit on. Ordinary canvas on top, coated fabric underneath.
• Add batting: lightweight batting in the middle saves you from hard ground, at the cost of weight. Weigh that against how far you carry it.
• It washes: unlike a plastic sheet you can put it through the machine, which changes how you feel about getting it out again.