Seam Allowance Opening Or Pressing To One Side

Definition and Overview

Seam allowance opening and pressing to one side are processes for smoothing seam allowances with an iron after stitching. Opening means spreading the left and right seam allowances away from the center of the seam, while pressing to one side means folding both seam allowances in the same direction. These processes affect the appearance of the finished surface, thickness, and comfort when worn.

“Opening press” is a term mainly used to refer to the opening process. On the other hand, “open seam” may also refer to a sewing specification in which the seam allowance is opened and finished, so its meaning range differs from pressing to one side, which simply describes an ironing operation.

Position in the Process

In general, after cutting, the parts are stitched, then the seam allowance is opened or pressed to one side before moving on to the next sewing process. On collars, facings, pockets, side seams, and similar areas, smoothing the seam allowance during the process makes the next seam joining position easier to stabilize.

Unlike the final finishing press done at the end of sewing, opening and pressing to one side are intermediate pressing steps that establish assembly accuracy. If this process is insufficient, seam twisting, overlapping seam allowances, or marks on the face fabric may appear in later processes or after finishing.

Method Selection and Procedure

Opening is suitable for areas where you want to distribute thickness around the seam to the left and right and keep the face side relatively flat. Pressing to one side is used when seam allowances can be gathered in one direction, such as in specifications that include topstitching to hold the seam allowance, or in areas where seam strength is needed.

In work, check the direction of the seam allowance and, if necessary, lightly press the seam first before opening it or folding it to one side. In curved areas, notches may be cut so the seam allowance does not pull, but the position and depth of the notches are determined according to the fabric and specification.

• Opening spreads the seam and distributes the thickness of the seam allowance.
• Pressing to one side keeps the folding direction consistent for all pieces.
• For materials that are prone to press marks on the face fabric, consider a pressing cloth and suitable pressing conditions.
• For materials with pile or texture, take care to avoid flattening or shine.

Ordering and Quality Considerations

In the specification sheet, clearly state for each area whether it is to be opened or pressed to one side, the direction if pressed to one side, and whether there is topstitching to hold the seam allowance. For products with left and right sides, it is also necessary to confirm whether the appearance will be symmetrical and which side should be pressed to one side as seen by the wearer.

Before mass production, confirm the pressing condition with a sample that combines the actual face fabric, interfacing, and lining. For materials that change easily with heat or steam, check for press marks, shine, shrinkage, surface irregularity, and seam puckering, and align the factory and working conditions.

Differences from Similar Terms

Seam allowance is the fabric allowance left outside the sewing line itself. Opening and pressing to one side refer to how that seam allowance is arranged and pressed after sewing. Edge finishing is a process for preventing fraying at the end of the seam allowance, and its purpose differs from opening and pressing to one side.

Fell seam sewing is a type of finishing in which the seam allowance is folded and sewn in so that it is enclosed. Pressing to one side is a basic operation that folds the seam allowance in one direction, but that alone does not make it a fell seam.

Frequently Asked Questions