Superwash vs. Non-Superwash Merino: Which Should You Choose?

If you spend any time browsing the shelves here at Yarn Atelier, you already know that Merino is the undisputed darling of the crafting world. But when you are choosing the perfect cone for your next project, you inevitably run into the biggest divide in modern textiles: Superwash versus Non-Superwash.

What exactly is the difference, and why does it matter so much for your finished fabric? Let’s unravel the science and behaviour behind both types of Merino so you can start your next project with confidence.

The Science of the Shrink

To understand the difference, you first have to look at how wool is built. If you look at a single strand of natural Merino under a microscope, it isn't smooth. It is covered in tiny, overlapping scales, much like the tiles on a roof or a pinecone.

When these scales are exposed to heat, moisture, and agitation (like the inside of your washing machine), they open up and permanently lock together. This process is called felting. It is wonderful if you are intentionally making a dense, weatherproof pair of slippers, but it is a disaster if you are trying to wash a lovingly knitted jumper or woven blanket.

This is where the fork in the road happens.

Superwash Merino

Superwash Merino has been specially treated to prevent those microscopic scales from locking together. Typically, the yarn undergoes an acid bath to remove the scales entirely, and is then coated in an extremely fine, microscopic polymer resin.

This process completely changes the physical properties of the fibre.

• The Feel: Because the scales have been smoothed over, Superwash Merino feels incredibly slick, soft, and dense. It has a beautiful, heavy drape.

• The Colour: Dyers love Superwash. That resin coating acts like a sponge for acid dyes, resulting in eye-wateringly vibrant and highly saturated colourways.

• The Catch: Removing the scales also removes the wool's natural "memory." Superwash garments are notorious for growing or stretching out when wet. You must always block Superwash swatches to see how much they expand, and always dry the finished garments flat.

Non-Superwash Merino

Often labelled as "untreated," "pure," or "heritage" Merino, this is wool exactly as nature intended, with all of its microscopic scales beautifully intact.

• The Feel: Untreated Merino is incredibly lofty and bouncy. Because the scales trap tiny pockets of air, it is significantly warmer and more breathable than its Superwash counterpart.

• The Structure: Those little scales act like microscopic velcro. When you work with NSW, the stitches "grab" onto one another. This is called "blooming," and it makes untreated Merino the absolute gold standard for colourwork, as the stitches meld together to hide any gaps or floats.

• The Catch: It will felt. You absolutely must hand-wash your NSW garments in cool water with a gentle wool wash, taking care not to aggressively rub or wring the fabric.

Quick Comparison

Which Should You Choose?

There is no "better" option — only the right option for your specific pattern.

Choose Superwash Merino for:

• Baby clothes: New parents do not have time to hand-wash garments.

• Shawls and wraps: The heavy drape of Superwash makes lace patterns open up beautifully.

• Next-to-skin accessories: The slick texture is incredibly gentle on sensitive skin.

Choose Non-Superwash Merino for:

• Colourwork yokes: The sticky fibres will create a cohesive, gap-free fabric.

• Cable knits: The natural bounce of untreated wool makes cables pop cleanly.

• Winter jumpers: It traps air much more effectively, keeping you significantly warmer.

Whether you are looking for the vibrant slip of a Superwash or the bouncy warmth of an untreated yarn, you can check superwash merinos here and non super wash merinos here.