Selecting initial size

Fitting exercise

Recap

In previous posts we discussed:

1. Everyone who uses a commercial pattern needs to decide on a starting size.

2. Starting size is generally guided by some type of body measurement.

3. The bust measurement on the pattern envelope is a reasonable starting point for size selection. However, bust circumference measurement is surprisingly challenging, for instance can vary according to the amount of bust compression in underwear. Because this measurement involves the body skeleton plus soft tissue it was considered an unreliable guide to select starting size and too often people found themselves with a toile that was too hard to fit.

4. The Sew/Fit method uses the front chest width measurement for a body measurement that circumvents the contribution of breast tissue and the Palmer Pletsch approach uses a high bust full circumference measurement.

5. Both approaches put the maker in a size smaller than the pattern size identified by a the full bust/chest measurement alone and so the pattern must be adjusted according to body measurements before making a toile.

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Theory of Pattern Alteration

Whether using front chest width or high bust measurement to select a starting size, the rationale is that:

1. Patterns are designed for individuals with B-cup breast sizes assuming a 2 inch difference between high bust and full bust. Unless otherwise stated, the high bust measurement for any pattern size can be assumed from a full bust measurement minus 2 inches.

2. Many patterns are designed with more ease and/or bigger shoulders than the maker needs.

3. It is preferable to start with a smaller overall size and then enlarge for the bust/chest circumference. It is widely considered more challenging to alter patterns in the neckline, shoulder and armhole area.

4. The Sew/Fit approach uses pivot and slide method to adjust the pattern prior to cutting. The difference needed is added equally to the front and back.

5. Palmer Pletch uses a body measurement taken in approximately the same body location as the Sew/Fit method but a complete circumference measurement (high bust). Because the high bust measurement includes the back, it is assumed that the front chest is the major contributor to the measurement difference and therefore the extra circumference is added to the front only. This also assumes that the the reason for a bigger front chest is breast tissue/larger cup size so the adjustment typically performed is the FBA (full bust adjustment).

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Practical Exercise

Today we will look at an practical example with these two approaches. Our example will assume an individual with a 4 inch difference between high bust and full bust. A 2 inch difference is accounted for by the standard B cup, so +2 inches extra needed represents the equivalent of a D cup.

Assuming a 2 inch grade between pattern sizes means that the the starting point will be one size smaller than that suggested by the full bust body measurement in the Palmer Pletsch method.

Pattern companies do not provide body front chest width measurements; it is probably a reasonable assumption that the selected size would be at least one size smaller so we will use the same starting size (one size smaller than full bust circumference) for consistency.

For this exercise I am using a commercial sloper from PatternLab.London. It comes with a single waist dart on the front which I changed to a single side dart before starting the comparison (a standard pattern manipulation).

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Increased bust circumference adding to the front only

A standard FBA is a slash and spread method. In this case, the difference was 2 inches total, so 1 inch per side.

Comparing to the starting pattern, the front has been adjusted to give extra circumference and also an increased front side dart size (depth) for the “larger” bust circumference. On the front, the armhole length is unchanged, the side seam length is unchanged, the pattern piece is longer, the bust line is lowered and the waistline is larger. The back was not altered.

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Increased bust circumference divided between front and back

In the Pivot and Slide method, the 2 inches of extra bust circumference needed is divided between the front and back, so ½ inch per side seam at bust level and a pivot mark is added to the pattern at the appropriate location.

Consult the Sew/Fit manual or Pattern Fitting With Confidence for a complete tutorial on how to perform this adjustment, the result is shown below:

2 inches of additional circumference has been added at the bust level on front and back. There is also a small increase in circumference on front and back at the mid-armhole level. The armhole lengths are the same as original, the waistline circumference is unchanged, the side seam distance and dart take up is the same, there are no length changes and the bust position is raised.

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Putting the pattern together

So far, we examined the outcome of the adjustments on the individual pattern pieces. But we did not look at how these pattern pieces connect to each other.

First let’s check what the side seam looks like when we sew up the dart. The seam line should be continuous, pattern makers refer to this as the “flow”.

The diagram shows how this looks for the original and the two adjusted versions. When superimposed (bottom far right) it is also clear that the side seams all have the same lengths.

Next let’s look at the flow between front and back at the armhole. To look at this all at once, I am showing a diagram where the back is matched up with a front at the bottom and top of the armhole, at the side seam and shoulder seam respectively. This is the original pattern, the seamlines flow smoothly between the two pattern pieces:

Now look at the P&S altered pattern pieces:

It’s subtle but there is a noticeable kink at the join of front and back at the armhole and the shoulder. This is because we pivoted the pattern pieces and so created a different angle than the 90˚ needed for a smooth intersection. The pivot was only ½ inch, had we pivoted further, this would be more noticeable.

The 2 inch FBA flows as well as the original pattern:

If we compare all three versions, here aligned along the lower curve of the back armhole the differences in alignment between the pattern pieces are very apparent. The P&S adjustment (pink), has a wider armhole base than the FBA adjustment (green). This affects how the 2D pattern pieces work together to create shape and how that shape interacts with the body to be read out as “fit”.

And finally a comparison with all three aligned at the HPS (high point shoulder):

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Conclusion

A garment is a complete architectural unit so it is important to examine how the 2D pattern pieces combine in 3D to understand the impact of different adjustments. We cannot evaluate or anticipate the impact of these (or other) adjustments without knowing more about the body. There really is no such thing as a “correct” pattern adjustment, rather the emphasis should be on understanding the assumptions behind different methods and also consequences of any adjustment(s) in order to find the optimum fit.

In this analysis we have examined two different ways of adding a the same amount (2 inches) of bust/chest circumference to a standard pattern. Importantly, we have seen that these two approaches result in different, clearly distinguishable pattern pieces. Each approach has a certain set of consequences that in turn impacts the overall architecture. From body measurements alone, we know increased circumference adjustments are needed to maintain the ease specified by the pattern but we might possibly need other pattern adjustments for optimum fit.

Unanswered Questions

What this exercise has not addressed are the assumptions behind starting with a smaller size and adjusting for bust/chest circumference.

We have seen that the P&S or FBA adjustments result in very different outcomes. Are there any consequences of the P&S or FBA adjustments that significantly alter the fit in unintended ways or have a detrimental impact? What if we just started with a pattern that corresponded to the full bust circumference size?

Is it truly worthwhile taking body measurements and doing all the pattern adjusting before cutting out the toile? A toile that we may have to adjust in other ways as well as chest circumference.

How robust and reliable is the theory of selecting a smaller pattern size then adjusting for bust/chest circumference? Can it be extended to different pattern companies and different styles? In other words, what are the advantages and disadvantages of starting with a size that corresponds to the full bust/chest circumference?

Coming Up Next

Answering the question(s) above will require a comparison of the adjusted pattern pieces with not the original starting size, but the size that we would have selected if we were choosing by full bust/chest circumference.

Comments and questions welcomed. And if you would like a small scale version of the pattern pieces with and without adjustments to play with please let me know.