A lab coat can make a fun costume for kids who are interested in science or medicine, and it can also double as a paint smock for art projects. To make a kid sized lab coat, you could buy a robe pattern and fabric and sew one from scratch, but you may find it easier to adapt an old, large long-sleeved men's shirt. You can use a button-down shirt with a collar, or a long-sleeved T-shirt, depending on the style you want. This no-sew version uses Stitch Witchery iron-on fusible web, which you can find in the notions section of many fabric stores.
Cut a slit down the centre of the front of the shirt, if you're using one that isn't button-down. Cut two strips of Stitch Witchery the length of the shirt, then fold the edges of the cut opening to the inside of the shirt. Slip the Stitch Witchery inside the folds, and press it with an iron to fuse it in place.
Cut a piece of hook and loop tape (commonly sold under the brand name Velcro) the length of the shirt opening (optional). You can use Stitch Witchery to attach the hook and loop tape, or buy iron-on Velcro. Separate the hook side and the loop side, and attach the hook side to the outside edge of one side of the shirt opening, and the loop side to the inside edge of the opposite side of the shirt opening. This will make the lab coat easy to open and close, even if it already has buttons.
Shorten the sleeves, if needed, by cutting off the ends and hemming the cut edges with Stitch Witchery.
Cut off the bottom edge of the shirt to shorten it or make it straight, if desired, and hem the edge with Stitch Witchery.
Add pockets to the lab coat (optional) by cutting rectangles of fabric that are about 1 inch taller and wider than you want the finished pocket. Fold the edges of the fabric over 1/2 inch toward the wrong side, and fuse them in place with Stitch Witchery. Position the pockets on the lab coat, and attach the side and lower edges to the shirt with Stitch Witchery. Leave the tops of the pockets open so the child can use them for lab supplies.
You may want to add a name to the front of the lab coat using fabric markers, or let kids use fabric markers to decorate the lab coat themselves.
Use caution when working with hot irons. Follow the manufacturer's directions for guidelines on using Stitch Witchery.