The lower thread used in machine embroidery, wound onto a small spool and housed within the bobbin case, forms the underside of the stitching. This specialized thread typically differs from the top thread, often finer and less visible, creating a smooth, balanced stitch. An example is polyester filament, chosen for its strength and subtle sheen.
This foundational component is crucial for the overall quality and appearance of embroidered designs. Its fine nature minimizes bulk, preventing designs from appearing stiff or raised. A suitable lower thread also contributes to tension balance, preventing puckering or thread breakage. Historically, cotton was commonly used, but advancements in textile technology have led to a wider array of materials, each optimized for different fabrics and design types.