Materials fabricate the designed artefact, but they can also play an important role in the design process; as a medium or method used to develop the design. Textiles can, with their soft and flexible properties, be easily transformed and altered in numerous ways; for example, by cutting, folding orprinting on the material. This transformative character makes textiles interesting sketching media for surface explorations when designing artefacts. The development of transformable materials; for example, fusible yarns and colour changing pigments, have expanded these inherent transformative qualities of textiles and have opened up the design field of smart textiles. Accordingly, this new material context has created a new area for textile designers to explore, where it is possible to enhance and play with the alterable character of their textiles, and control their transformation through physical manipulation and programming. However, these expanded transformative properties also open up a new task for textile designers; to design "smart textiles as raw materials for design". By this term we mean, textiles that are not finished in their design but that can be developed and enhanced when they take part in a product or space design process. In this article, we explore and start to define what smart textiles as raw materials for design can be, and look at how these materials can come into and add something to another design process. The foundation for this exploration is a number of textile examples from the “Smart Textiles sample collection” and our experiences when developing and designing with them. (The Smart Textiles sample collection is a range of textiles that is designed and produced by the Smart Textile Design Lab, to give students, designers and researchers direct access to different types of smart textiles). The possibilities and limitations of smart textiles as raw materials for design are explored by looking at the textile examples from two perspectives: firstly, by looking at the considerations that come with designing this type of textile design, and secondly by looking at what these transformative textiles can bring to another design process. Each example is analyzed and classified according to what transformable design variables for structure and surface change can be embedded in the textile design, and what design variables this subsequently creates for a design process that uses these materials i.e., describing what type of transformation different examples of smart textiles introduce to the design process/design space; whether the change is reversible or irreversible, and whether the change occurs through physical or through digital manipulation of the material. This article ends with a discussion of how smart textiles in the form of raw materials for design could influence how we design textiles and how we design with textiles. Can transformative materials enrich material explorations in a design process? Can further development and alteration of the material design be introduced or defined by the textile designer? Could smart textiles as raw materials for design open up a stronger connection between the design of textiles and the design of the product or spaces where they will be used?