Background and Context: While assessment of computational thinking concepts, practices, and perspectives is at the forefront of K-12 CS education, supporting student "communication about computation" has received relatively little attention. Objective: To examine the usability of process-based portfolios for capturing students' communication about their computational practices regarding the process of making electronic textile projects. Method: We examined the portfolios of 248 high school students in 15 introductory CS classrooms from largely underserved communities, using a formal rubric (top-down) to code computational communication and an open-coding scheme (bottom-up) to identify computational practices described. Findings: Students demonstrated stronger abilities to communicate about computation using text than visuals. They also reported under-assessed CT practices like debugging, iterating, and collaborating. Students of experienced e-textile teachers performed substantially better than those with novice e-textile teachers. Implications: Portfolios provide a viable addition to traditional performance or survey assessments and meet a need to promote communication skills.