This paper contributes a framework for articulating biomaterial affordances as situated, temporal and relational. These affordances are often difficult to articulate because they are not fixed properties of materials but shifting possibilities that become perceptible through making, handling, environmental exposure and time. Grounded in research-through-design and a retrospective synthesis of first-person material-led biodesign practice, the framework proposes six analytical dimensions – tactile, visual, auditory, olfactory, kinesthetic and responsive – as relational lenses for attending to, articulating and designing with biomaterial affordances. Through examples from gelatin biofoam tangible interaction, dissolving wearables and comparative analysis of published biomaterial systems, the paper shows how biomaterial affordances may emerge through both immediate qualities such as softness, compressibility and tactile feedback and slower transformations such as swelling, dissolution, aging and environmental responsiveness. The framework supports biodesigners and researchers in making tacit material knowledge more legible and tracing how biomaterial affordances surface, overlap and chain together in ways that reshape subsequent design decisions, while foregrounding transformation as a design resource.