Reading a mock-up: what the wrinkles are telling you

Fabric held under tension can only fail in a few ways, and each produces a wrinkle running perpendicular to the direction of the problem. That single principle turns fitting from guesswork into reading.

Horizontal wrinkles mean vertical excess — too much length somewhere. Vertical wrinkles mean horizontal excess — too much width. Diagonal wrinkles point along their own length towards the place that is short or the place that is being pulled, which is why they are the informative ones and also the ones beginners find hardest.

The other thing worth establishing before the first mock-up: it is supposed to be wrong. Two or three is normal for a first corset and experienced makers still expect at least one. A mock-up that fits perfectly first time usually means the pattern was drafted to a shape somebody had already fitted.

Horizontal wrinkles

Too much length

Vertical wrinkles

Too much width

Diagonal wrinkles

Point towards what is short or pulling

Mock-ups for a first corset

Two or three, and that is normal

1. 1

   Step 1: Make the mock-up in something that behaves like the real thing

   Coutil or a firm twill. A soft calico stretches and lies to you, and a mock-up that lies is worse than no mock-up — every fault will read as smaller than it is.

   You will know it worked when: Faults that are real.

2. 2

   Step 2: Bone it, at least partially

   An unboned mock-up hangs completely differently under tension. Even a few bones at the seams changes what you are looking at.

   You will know it worked when: A garment behaving like a corset.

3. 3

   Step 3: Lace it to the gap you actually intend

   Fitting a mock-up closed and then wearing the corset with a two-inch gap means you fitted the wrong garment. Decide the gap first and fit to it.

   You will know it worked when: The right circumference.

4. 4

   Step 4: Mark on the mock-up, in pen, while it is on

   Draw the wrinkles, mark where the waist actually sits, mark where the edges want to be. Memory after taking it off is unreliable and the mock-up is disposable.

   You will know it worked when: A record you can pattern from.

5. 5

   Step 5: Change one thing at a time

   The commonest way a second mock-up is less informative than the first is fixing four things at once and being unable to attribute the result.

   You will know it worked when: A second mock-up that teaches something.

6. 6

   Step 6: Transfer the changes to the pattern, not to the mock-up

   The pattern is the thing you keep. A beautifully corrected mock-up with an uncorrected pattern is a wasted afternoon.

   You will know it worked when: A pattern that improves each time.

• How many mock-ups should a first corset take? — Two or three is normal, and experienced makers still expect at least one. A mock-up is made in order to be wrong — that is its function. A first mock-up that fits perfectly usually means the pattern was drafted to a shape somebody had already fitted.
• What do diagonal wrinkles mean? — Follow the wrinkle. Fabric wrinkles perpendicular to the direction of excess strain, so a diagonal wrinkle points from the excess towards whatever is pulling or is short. They are the most informative marks on a mock-up and the ones beginners find hardest, because the cause is usually not where the wrinkle is.
• Can I use calico for the mock-up? — You can, and it will mislead you. Soft calico stretches under tension in a way coutil does not, so every fault reads as smaller than it is and the corset made from the corrected pattern fits differently. Use coutil or a firm twill, and bone it at least partially — an unboned mock-up hangs nothing like the finished garment.