Day 17: Why Do My Pants Get Baggy? (The "Lazy Cotton" Theory)

Day 17: Why Do My Pants Get Baggy? (The "Lazy Cotton" Theory)

Welcome to Week 3, Day 17 of My Dad vs. The Algorithm.

Today we are talking about The Baggy Knee.

A designer recently asked my dad, Ira: "I want to make a skinny legging, but I want it to be 100% Cotton because my customers hate synthetic fabrics. Can you recommend a heavy cotton that won't bag out at the knees?"

 100% cotton has stretch, but it likes to take a nap once it's stretched out (hello, baggy knees). If you want your fabric to "snap back" like a rubber band, you need that "Spandex Power."

Ira shook his head before the question was even finished.

Ira’s Reaction:

"Cotton is lazy. You stretch it out, and it decides to take a nap right there. It doesn't want to go back home. If you want the fabric to snap back to your ankle, you need Spandex. You can't ask for '100% Natural' and then complain when it acts like a plant instead of a rubber band."

Here is the difference between Stretch and Recovery.

Stretch vs. Recovery

Most people think these are the same thing, but they are opposites.

1. Stretch: The ability of the fabric to grow wider when you pull it.

2. Recovery: The ability of the fabric to return to its original shape when you let go.

100% Cotton has natural "mechanical stretch" because the knit loops can distort and widen. However, cotton has poor recovery. Once the fibers slide past each other, they stay there until you wash them. This is why 100% cotton jeans feel tight in the morning and loose in the afternoon.

The Role of Spandex (Elastane)

If you are making something tight-fitting (Leggings, Bike Shorts, Fitted Tanks), you must use Spandex.

Think of Spandex as a microscopic rubber band woven into every stitch.

• When you bend your knee, the cotton stretches.

• When you straighten your leg, the Spandex pulls the cotton back into place.

The "95/5" Rule

For most fitted garments, the magic number is 95% Cotton / 5% Spandex. This gives you the soft "hand" of cotton with the "memory" of Spandex.

• 100% Cotton: Great for sweatpants, oversized hoodies, and t-shirts. (Things that drape).

• Cotton/Spandex: Mandatory for leggings, bodysuits, and cuffs. (Things that cling).

Ira’s Take:

"Don't fight the physics. If you want tight, you need the rubber. If you want natural, you have to accept the 'baggy knee.' You can't have a 100% cotton legging that stays tight for 12 hours. It doesn't exist."

The Bottom Line

If you are designing a garment, ask yourself: "Do I want this to drape, or do I want this to hug?"

• Drape = 100% Cotton.

• Hug = Cotton/Spandex.

Ira’s Final Advice:

"Cotton is comfortable, but it has no memory. If you want your pants to remember the shape of your leg, add 5% Spandex."

Tune in tomorrow for Day 18!

(Missed yesterday's post about the No Cut Rule? Read Day 16: I Can't Fix Confetti here.)

Need good recovery? Check out our Spandex French Terry collection.