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ISO, ASTM, and ABC Seams… why are they different?

If fashion design is your thing, you will agree that, when making clothing, the seams are, what architectures would call, the pillars of the assembly. And the fact is that important aspects such as the look, quality, and durability of the garment will depend on them.

In a previous article (see article here), we talked about the international systems of seam codes. Now, in this article, we are going to explain the differences between ABC Seams and ISO/ASTM seams.

What differentiates ABC Seams from ISO seams?

If you are an experienced designer or product developer, you will know that speaking the same language as your factory is essential. And by language, we mean the way you explain your designs, as this will determine how well (or not!) you receive the prototypes.

The 5 most important differences between ISO and ABC Seams.

1. Representation of seams (sketch or diagram):


“All seams are shown as sewn on a machine.
In the case of multiple operations, they are shown as sewn after the final operation” (*1) 
That is, the seam is represented according to the position of the fabric at the end of the last operation on the sewing machine.
The fabric handling steps after sewing are not considered in the seam sketch.

ABC Seams

The seam is represented as seen on the finished garment. And the right side of the seam is always shown facing up.

2. Classification:


“Seams are divided (…) according to the types and minimum number of components within the seam” (*1), classifying them according to the position of the fabrics at the time of sewing:

  1. Superimposed
  2. Lapped
  3. Bound
  4. Flat
  5. Ornamental
  6. Edge Finishing

ABC Seams

Seams are classified into 3 categories according to their main function:

  1. Construction
  2. Finishing
  3. Details

That makes their search much faster and easier. 

If you want to know more about seam classification, read this article: Seam Classification.

These are the two most important differences. But they are not the only ones.

3. Seam Codes

ISO codes may change with each revision. In contrast, ABC Seams codes never change regardless of the year.

4. Seam sketch understanding

Have you tried to use ISO / ASTM seams and felt frustrated because you don’t understand the sketches? Don’t get depressed, this is very common. Especially if you don’t know how to sew. To be able to interpret the ISO / ASTM seams, you must know how to sew. Because as we told you before, their seams are represented according to the position of the fabric at the last sewing operation.

However, to use ABC Seams you don’t need to know how to sew (although we do advise you to do so!!).
The only requirement for interpreting the ABC Seams sketches is that you know how the seams should look on the garment. You simply tell the factory what you want and they, as professionals, will know how to do it.

5. Seam sketch color

 Color does make a difference. Because unlike ISO and ASTM which represent their seams (including stitches) in black color, at ABC Seams we use different colors to differentiate the fabrics of the stitches.

We know how discouraging it is that after so much work, time, and money invested to develop your designs, you receive prototypes that have nothing to do with what you expected. Many times this happens because the factory did not understand your explanations

Whether you are a student, a teacher, or an industry professional, we hope this article will help you understand the main differences between these three international sewing standardization systems. 

If you have any questions, you can write us in the comments below or contact us at


ABC Seams® 

References and bibliography:

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