Acrylic yarn has earned its place in nearly every craft basket — and for good reason. It’s affordable, colorful, durable, and widely available. But one question keeps popping up in knitting circles, crochet communities, and laundry rooms alike: does acrylic yarn shrink?
The short answer is: not the way you’d expect. Acrylic doesn’t shrink like wool. But that doesn’t mean it’s invincible. Under the wrong conditions, acrylic yarn can warp, melt, stretch, or lose its shape entirely. Understanding exactly how acrylic behaves — and why — can save a finished project from disaster.
What Is Acrylic Yarn Made Of?
Before diving into shrinkage, it helps to understand what acrylic yarn actually is.
Acrylic yarn is a synthetic fiber made from a polymer called polyacrylonitrile, derived from fossil fuels through a chemical process. Unlike wool, cotton, or linen — which come from animals or plants — acrylic is entirely man-made.
Think of it this way: wool is a living fiber that remembers warmth and moisture. Acrylic is more like a plastic cousin — it doesn’t breathe, doesn’t absorb water the same way, and responds very differently to heat.
Key Properties of Acrylic Fiber
| Property | Acrylic Yarn | Wool Yarn |
|---|---|---|
| Origin | Synthetic (petroleum-based) | Natural (animal fiber) |
| Heat sensitivity | Melts/warps under high heat | Shrinks/felts under heat + agitation |
| Water absorption | Low | High |
| Elasticity | Moderate | High |
| Shrinkage risk | Low (but warping possible) | High |
| Washing ease | Machine washable (cool/warm) | Requires gentle hand wash |
Does Acrylic Yarn Actually Shrink?
Here’s the honest truth: acrylic yarn does not shrink in the traditional sense. Shrinkage — the way fibers pull inward and tighten — is a protein-fiber behavior. It happens when wool scales interlock under heat, moisture, and agitation. Acrylic doesn’t have scales. It has smooth, plastic-like strands.
So instead of shrinking, acrylic does something potentially worse under heat: it melts, warps, or permanently distorts.
What Happens to Acrylic in Heat?
- Low heat (warm water, cool dryer): Acrylic holds its shape beautifully. No damage, no distortion.
- Medium heat (warm dryer, hot water): The fibers may begin to soften slightly. Repeated exposure can cause gradual stretching or slight stiffness.
- High heat (hot dryer, iron directly on fabric, boiling water): This is the danger zone. Acrylic fibers can permanently melt, flatten, or harden. Once it’s melted, there’s no going back — no amount of rewashing will fix it.
A melted acrylic sweater doesn’t shrink into a smaller version of itself. It transforms into something stiff, shiny, and unwearable. It’s the yarn equivalent of leaving a plastic bottle on a hot car dashboard.
Can You Shrink Acrylic Yarn on Purpose?
Crafters sometimes want to “felt” or shrink a finished piece to tighten the stitches. With wool, this works through agitation in hot water. With acrylic, deliberate shrinkage is nearly impossible using standard felting techniques.
Why Felting Doesn’t Work on Acrylic
Felting relies on the microscopic scales on wool fibers tangling together permanently when exposed to heat, moisture, and friction. Acrylic fibers are smooth at the microscopic level — there are no scales to lock together. Hot water and vigorous washing will simply stress the fibers without compacting them.
Some crafters try to “kill” acrylic yarn — a technique involving steam or a hot iron over a damp cloth — which softens and flattens the fibers to block a project. This isn’t shrinking; it’s the opposite. It relaxes and stretches the stitches, giving them a smoother, drapier finish. Once you “kill” acrylic yarn, that change is permanent.
When Acrylic Yarn Loses Its Shape
Even though it won’t shrink, acrylic yarn projects can still go wrong in the wash. Here’s what typically causes shape issues:
Stretching vs. Shrinking
Acrylic is more likely to stretch than shrink. Heavy acrylic garments — like large blankets or sweaters — can pull downward when wet because the fiber absorbs water weight while temporarily losing structural integrity. Laying items flat to dry prevents this.
Pilling
High agitation in a washing machine causes acrylic fibers to break and roll into small balls on the surface. This isn’t shrinkage, but it does affect the look and feel of the fabric significantly.
Heat Damage Indicators
| Damage Type | Cause | Appearance |
|---|---|---|
| Shiny, flattened texture | Direct iron contact | Permanently glossy patches |
| Stiff, crunchy feel | High-heat dryer | Loss of softness and flexibility |
| Melted fibers | Extreme heat exposure | Fused, plastic-like areas |
| Stretched-out shape | Wet weight + gravity | Elongated, misshapen garment |
How to Wash Acrylic Yarn Safely
Washing acrylic correctly isn’t complicated — it just requires respecting the fiber’s one real enemy: excessive heat.
Step-by-Step Washing Guide
- Check the label. Most commercial acrylic yarn is machine washable. Look for the washtub symbol with a temperature rating.
- Use cool or lukewarm water. Anything above 40°C (104°F) risks gradual damage with repeated washing.
- Choose a gentle cycle. Less agitation means less pilling and fewer stretched fibers.
- Use a mild detergent. Harsh chemicals can break down synthetic fibers over time.
- Skip the dryer or use low heat only. A cool tumble dry is usually fine, but high heat is the enemy.
- Lay flat to dry. For garments and accessories, this preserves shape far better than hanging.
Acrylic Yarn Blends: A Special Case
Not all “acrylic” yarns are 100% acrylic. Many popular yarns are blends — acrylic mixed with wool, cotton, bamboo, or nylon. These blends behave differently than pure acrylic.
Common Blends and Their Behavior
| Yarn Blend | Shrinkage Risk | Care Notes |
|---|---|---|
| 100% Acrylic | Very low | Machine wash, avoid high heat |
| Acrylic/Wool blend | Moderate | Hand wash or gentle cold cycle |
| Acrylic/Cotton blend | Low to moderate | Cold wash recommended |
| Acrylic/Nylon blend | Very low | Very durable; machine washable |
| Acrylic/Bamboo blend | Low | Gentle cycle; lay flat to dry |
The key rule: always follow the care instructions for the most delicate fiber in the blend. An 80% acrylic, 20% wool yarn should be treated like wool — because that 20% will absolutely felt and shrink if you throw it in a hot wash.
Blocking Acrylic: Shaping Without Shrinking
Blocking is a finishing technique that helps knit and crochet projects reach their intended dimensions and shape. With natural fibers, wet blocking is the go-to method. With acrylic, steam blocking (also called “killing” the yarn) is the preferred approach.
How to Steam Block Acrylic Yarn
- Pin the finished piece to a foam blocking mat in the desired shape.
- Hold a steam iron 2–3 cm above the surface — never let it touch the acrylic directly.
- Move the iron slowly across the piece, allowing steam to penetrate the fibers.
- Let it cool and dry completely before unpinning.
The result is a flatter, more defined piece with relaxed stitches. This technique permanently changes the fiber’s structure, so it’s best used for final finishing — not experimentation.
Key Takeaways
- Acrylic yarn does not shrink the way wool does — it lacks the protein scales that cause fiber shrinkage.
- High heat is acrylic’s true weakness; it causes melting, warping, and permanent distortion, not shrinkage.
- Acrylic blends containing wool or other natural fibers can shrink — always care for the most delicate fiber in the mix.
- Washing in cool to lukewarm water on a gentle cycle keeps acrylic projects safe and long-lasting.
- Steam blocking can permanently reshape acrylic projects, but this process is irreversible.
Frequently Asked Questions (FAQ)
Can acrylic yarn shrink in the washing machine?
Pure acrylic yarn is highly resistant to shrinkage in the washing machine. However, washing in hot water can cause the fibers to warp or stiffen over time. Always use a cool or warm cycle to keep your projects looking their best.
What happens if you put acrylic yarn in a hot dryer?
High dryer heat can melt, flatten, or permanently stiffen acrylic fibers. Unlike wool, which shrinks, acrylic can lose its softness and become crunchy or shiny. A low-heat or air-dry setting is always the safer choice.
Why does my acrylic yarn project feel stiff after washing?
Stiffness after washing usually points to heat exposure or a harsh detergent breaking down the fibers. Try washing again in cold water with a gentle detergent and laying it flat to dry — though if the fibers have already been heat-damaged, the change may be permanent.
Can you felt acrylic yarn like wool?
No — acrylic yarn cannot be felted. Felting works through the interlocking of protein fiber scales, which acrylic doesn’t have. Agitating acrylic in hot water will not compact the fibers; it will simply stress them and cause pilling.
How do you shrink an acrylic sweater that’s too big?
Truthfully, you can’t reliably shrink a 100% acrylic sweater. The fiber resists compaction. Your best option is to take it to a tailor for alteration, or try steam blocking to slightly reshape specific areas.
Does acrylic yarn stretch out over time?
Yes — acrylic yarn can stretch, especially in heavy garments that are washed frequently or hung while wet. The fiber loses some elasticity with heat and repeated mechanical stress. Laying items flat to dry significantly reduces this issue.
Is acrylic yarn safe for baby items in the wash?
100% acrylic yarn is generally very safe for baby items because it’s machine washable and hypoallergenic for most people. Just always use a gentle, fragrance-free detergent and a cool-water cycle to keep the softness intact.
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