======Blood Spatter Patterns======


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**Alternative titles:** Effect of Drop Height on Bloodstain Diameter
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====Summary====                   
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====Procedure====  
  -Gather materials: chart paper, fake blood, disposable pipette, metric ruler, yardstick or meter stick, markers, and optional step stool/ladder with supervision.
  -Tape chart paper to a flat, horizontal surface and label trial areas with intended drop heights (for example: 0.5 ft, 1 ft, 3 ft, 5 ft, 7 ft, 9 ft).
  -Practice releasing a single drop from the pipette without adding sideways motion; keep the tip aligned directly above the target.
  -Measure and mark the release height from the paper using the yardstick/meter stick; keep the pipette tip at this height for every trial at that level.
  -Release one drop onto the target area; allow the stain to stop spreading before measuring.
  -Measure the diameter of the circular portion of the stain (ignore satellites for the primary diameter) and record the value on the chart paper and in a data table.
  -Repeat at least 3 trials per height to improve reliability, refilling the pipette to a consistent volume each time.
  -Increase heights as safely permitted; if testing above table height, use a step stool or supervised ladder and ensure the paper surface and release point remain aligned vertically.
  -Optionally test different volumes (small vs. full pipette) to see how volume influences stain size; record volumes used.
  -After all trials, calculate mean diameter for each height and plot diameter (y) versus height (x); identify any plateau that suggests terminal velocity conditions.
  -Inspect patterns for satellites, scalloped edges, or elongation; note how surface type and repeated drops in the same spot can alter the pattern.
  -Clean the area following lab safety procedures.



====Links==== 
Blood Spatter: How to Make Spatter - Heidi Hisrich: 
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📄 Blood Spatter Inquiry Lab - The Trendy Science Teacher: [[https://thetrendyscienceteacher.com/2023/01/13/blood-spatter-inquiry-lab-3/]]\\

📄 Forensics: How Does It Matter? Measure the Spatter! - Science Buddies: [[https://www.sciencebuddies.org/science-fair-projects/project-ideas/Phys_p066/physics/forensics-measure-blood-spatter]]\\

====Variations====
  *Test different surfaces (copy paper, cardboard, tile, fabric) to compare how surface texture affects spreading and satellites.
  *Keep height constant and vary drop volume to model the effect of volume on stain diameter.
  *Keep height and volume constant but change the surface angle (0° vs. a gentle incline) to observe elongation and directional tails.
  *Compare different fake blood formulations (with and without thickener) to explore viscosity effects.
  *Use image analysis software or graph paper overlays to measure diameters more precisely and to quantify satellite counts.



====Safety Precautions====
  *Use only fake blood; never use real blood.
  *Wear safety glasses and gloves to prevent contact and stains.
  *Do not ingest materials; keep food and drink out of the lab area.
  *Secure chart paper with tape to prevent slipping hazards from spills.
  *If standing on lab stations, verify they are sturdy, dry, and uncluttered; step up and down carefully and only with teacher permission.
  *Use a step stool or ladder only with adult supervision; maintain three points of contact and keep the yardstick/meter stick clear of others.
  *Wipe spills immediately with appropriate cleaner; dispose of paper and gloves according to classroom guidelines.
  *Wash hands after the activity.




====Questions to Consider====
  *How did stain diameter change as height increased, and did it level off at higher heights? (Diameter typically increases with height until it approaches a maximum when the drop reaches near-terminal velocity.)
  *Why might two groups get different diameters at the same height? (Differences in drop volume, release technique, pipette squeeze force, or surface texture can change results.)
  *What features indicate higher-energy impacts besides larger diameter? (More pronounced scalloped edges and increased satellite spatter are typical at higher impact energy.)
  *How would a rough or absorbent surface affect the stain compared to a smooth, nonabsorbent surface? (Rough/absorbent surfaces usually reduce spreading and can suppress satellites, producing smaller, less defined edges.)
  *If the drop is released with sideways motion, what happens to the shape? (The stain elongates in the direction of travel and may show a tail pointing in that direction.)