Give each sample a readable comparison point
Place a plain label beside the sample that names the control and the one variable being explored. A label can make a photo useful weeks later without asking the viewer to infer what changed. It does not turn an exploratory observation into a guarantee about a material.
Record what the image cannot show
Add a short note about lighting, the viewing angle, or anything else that might affect interpretation. This helps preserve honest context when comparing a later test. Browse /updates/ for more sample-documentation habits.