Testing Your Ultrasonic Works

Not sure that your ultrasonic is working properly?

The foil test is one test that can tell you if  it is.

Foil Test

The foil test is commonly used in medical, vet and dental practices, before the start of each day.  It is critical that surgical instruments are properly cleaned, then sterilised.  A properly functioning ultrasonic cleaner is the key to an effective cleaning process.


  1. Fill the tank with the recommended amount of water and add a squirt of dishwashing detergent.  Detergent will help to soften the water.
  2. Degas the water in the tank.  Set heater thermostat to 60C.  After temperature is achieved run unit on cleaning cycle for about 10 minutes.  Degassing will expel the air so that the unit operates at optimum level.
    • NB If your machine does not have a heater you can boil water in a kettle to get the same result.  In a boil proof jug add two parts boiling water  to one part tap water.  If the tap water is room temperature (25C), the combined water will give you about 60C.  Adjust the mix for your local conditions.

Test Procedure

You will need a piece of kitchen aluminium foil large enough to cross the tank diagonally and to drop towards (but not quite to) the bottom of the tank, with some excess foil above the water, that you can hold onto.   The foil should be oriented vertically (ie hanging downwards) – if it is laid horizontal the test will be invalid. NB Do not allow body parts to touch or be immersed in the tank water at any time during cleaning operation.

passed foil test

Typical Result – 90 seconds in 100W Ultrasonic Cleaner

Run ultrasonic cleaner through a 10 minute cycle, while holding the foil above the water line, with the foil descending to just above the bottom of the tank, and hanging diagonally across the tank.

Remove and inspect foil.  A functioning ultrasonic cleaner will show evidence of the cavitation effect on the foil.  The more powerful the machine the more intense the reaction.  This may range from pin sized indentations in a light weight machine of say 30W, to foil being ripped to shreds in a larger unit (say 100W+).  Lack of indentations is a sure sign that machine is not working properly.  If you performed this test after delivery from the supplier you should advise the supplier and request return/replacement instructions.

Warning:  Some cheaper machines are named in a way that will deliberately mislead the buyer.  Unless the machine clearly states that it is an ultrasonic cleaner  customers should assume that it is not.   Ultrasonic cleaning pretenders will never pass the foil test.  Contact the supplier or your local Department of Fair Trading for further advice.

NB If you are in a medical/dental practice consult your practice manager or your practice procedure manual. Medical practices in Australia should refer to AGPAL if they need specific guidance.

Liquid Glass Oz designs quality ultrasonic cleaners for commercial operations in Australia and New Zealand (N18973)