Sustainability is one of the most common terms in public discourse. But what is sustainability? While social practice theory has advanced understanding of routines and social action, fewer studies trace how sustainability is produced within material production systems and across scales. This study conceptualises sustainability as an emergent feature of how social-ecological relations are configured and transformed through practice. Combining practice theory, object biography and relational political economy, it follows wool and silk across four nodes of the Albanian animal fibre supply chain, from shepherding and sericulture to industrial manufacturing. The analysis shows how practices are continuously configured through relations between fibres, skills and meanings, and how fibres actively shape the practices that surround them. Sustainability emerges where practices remain closely aligned with ecological conditions and declines as these connections are broken through commodification, scalability and alienation. The push and pull between practices and materials reveals how human action and ecological conditions continuously remake each other rather than operating as distinct domains. The study contributes to the sociology of sustainability by grounding an abstract concept in lived material realities and offering a transferrable analytical approach for tracing how social-ecological relations are maintained and reshaped across contemporary production systems.