Test tube & bung
Test tube rack
Measure out equal volumes of oil and water (4 ml of each works well)
Add to test tube - water first.
Add in volume of emulsifier to be tested - do not use more emulsifier than oil/water.
Insert bung, hold in place with thumb and invert the tube 10 times.
Immediately start the stopclock and place the tube in the rack.
When you can see a clear separation of oil and water stop the stopclock and record the time.
Repeat three times for each volume of emulsifier if you have time.
Instead of different volumes of emulsifier you could try the same volume of different types of emulsifier.
Any spills of oil/water could be hazardous, as could broken glassware. Clean up any spills/breakages immediately.