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Foil test

Functional test of an ultrasonic bath

For the functional test of an ultrasonic bath, the foil test is recommended - at initial commissioning, then at regular intervals (e.g. ¼-yearly). The frequency of the test is the responsibility of the user. The foil test is a simple procedure for displaying the intensity and distribution of cavitation in an ultrasonic bath. For this purpose, an aluminium foil stretched on a foil test frame is inserted. This is perforated or destroyed by cavitation to a certain degree depending on the sonication time.

For the reproducibility of the test results, it is important that the test conditions are always the same:

- Filling the oscillating tank up to the filling level marking
- Temperature of the sonication fluid
- degassing time
- Positioning the frame
- Film type (brand, thickness)
- sonication duration
- Type and concentration of the ultrasound preparation

Carrying out the foil test

  1. Fill the oscillating tank with water and suitable ultrasound preparation in the dosage specified by the manufacturer up to the filling level mark.
  2. Degas liquid (see instructions for use)
  3. Stretch aluminium foil (household foil 10 μm to 25 μm thick) onto the foil test frame.
    Depending on the size of the tub, the frame may protrude.
    It is sufficient to cover the dipping frame part.
  4. With the ultrasound switched off, place the covered foil test frame at an angle in the centre of the oscillating tank, fix if necessary, see video.
  5. Switch on ultrasound and sonicate the film for at least 1 minute until visible perforation or hole formation occurs.
    With more stable films (thicker or coated), the sonication time can be up to 3 minutes.
  6. Switch off the ultrasound, remove the foil and let it dry.
  7. The foil must be perforated, see picture. Otherwise, an inspection of the device by the service department of BANDELIN electronic GmbH & Co. KG is recommended.
  8. Archiving of the foil with test date and serial number of the ultrasonic bath. In addition, the documentation template for the foil test can be filled out and archived.
  9. After the test, the oscillating tank must be rinsed thoroughly to remove any foil particles that have come out.

PDF file hdownload

Folio Test Documentation Sheet

The BANDELIN Foil test documentation sheet facilitates the documentation of the functional test of an ultrasonic bath

Liquid for the foil test:
In order to obtain sufficiently strong cavitation, the interfacial tension of the water used must also be reduced for the foil test with the help of preparations containing surfactants.
We recommend the following ultrasound preparations:


If none of these preparations is available, a neutral or mildly alkaline preparation that does not destroy aluminium should be used. The preparation must be approved by the manufacturer for use in the ultrasonic bath.

Test result and documentation:
If the test conditions are always the same, the test result is to be assessed according to the perforated area of the films. The perforated areas of the films should always have approximately the same extension and distribution - they are never congruent.
Regular foil tests are the only way to ensure constant process monitoring, e.g. for the reprocessing of medical devices.

The slides can also be archived in a suitable manner (scan, photo, etc.). This makes it possible to compare the slides at any time.

As an alternative to the foil test, the hydroacoustic measurement method according to
IEC TS 63001
Further explanations of this measuring method can be found at cavispector.com.


Example application in the video

We have put together an overview of sample cleanings for you to carry out an optimal US cleaning.

For every application the right


Application & Help

More tips & info

Further practical tips and assistance for our ultrasonic baths and their use can be found in our Knowledge Base under Practical Tips. Of course, you are also welcome to contact us if you have any questions regarding the devices or their use.

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