The base yarn of Tulla Tweed is quite fine. To achieve a thicker yarn, this fine base is braided like an i-cord, creating a casing with a hollow center. This design makes the finished garments lightweight, reduces the likelihood of pilling, and traps heat within the hollow core for added warmth.
When working with Tulla Tweed, designer Louisa Harding recommends using a larger needle size than what you would typically use for standard plied yarns to achieve the same gauge. This allows the yarn to stretch properly. If you stick to the same needle size as you would for a traditionally plied yarn, the resulting fabric will be too dense. It's essential to swatch when substituting with Tulla Tweed for another pattern.
