4. Open the agar plate (catalog no. H21) and apply the sample by swabbing the entire surface of the agar.  Turn the plate 90 degrees and swab again to ensure that all areas of the plate are inoculated.  Do not leave any area of the plate uninoculated by the swab.

5. Dispense three paper disks from the disk cartridge (blank disks Catalog. No. Z7121) by peeling them off with tweezers.  Place each disk into an a separate empty petri dish (Catalog No. 330120).

6. Prepare your test substances.

7. Apply test substance to the disk until it is saturated.

8. Do the same with all the test substances.

9. Place the first test disk, saturated with the test substance...

...onto the agar plate.

10. Do the same with the last two test disks...

...keeping them separated and not too close to the edge of the plate.

10. Put the lid on the plate and tape lid shut using ordinary clear tape.

11. Don't forget to mark the back of the Petri dish with the name of the oral disinfectant associated with the paper disk.

12. Put the plate, with the media side up, somewhere warm such as the top of your refrigerator.  Cover the plates so light does not shine on the agar.  Allow to incubate for 4-5 days.  Do not heat over 36 Celsius (97 Fahrenheit).

13. After 4-5 days, measure the zones of non-growth (inhibition) around each disk.  The larger the zone of non-growth the more effective the test substance is against the microorganisms.