In our previous blog of this the Integrity test series, we talked about the Water Intrusion test (WIT). In this article we continue onto the Bubble Point test.
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Bubble Point Test (BPT) measures the minimum differential pressure required to form a bubble through its largest pores present in wetted filter media / membrane of the cartridge. It is generally used to identify the presumed pore rating of a membrane. It represents the force necessary to break the bond of the intermolecular attractions that characterize the wetting of the filters solid surface by the liquid. There is always a diffusion of air before the bubble point test initialized. For every 10° C there is approx 2% change in the bubble point value.
Bubble point shows the flow of air forming a bubble through its largest pores present in the membrane of the cartridge.

Merits
- One of the great advantages of the bubble point test is that it can be performed of filters under actual use conditions and with any filter. 
- It is a non-destructive test, thus it does not contaminate the filter and so can be used to determine the integrity of a filter at any time, as well as establishing the absolute rating.
- In the future, with further advantages in computer software and control, it may be possible to use the data on flow rate or pressure increases to more accurately determine what happens in a sample before the bubble point is reached, such as diffusion.
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Demerits
- Ensure that the filter is thoroughly and uniformly wet as per wetting procedure. Any dry pores in the membrane will result in test failure.
- Contamination of the filter should be avoided as it can adversely affect the wetting of the membrane thus resulting in a false failure.
- There is always a diffusion of air before the bubble point test, this pre-mature air flow should not be assumed as bubble flow observation while performing manual test. 
- Failure to wet the filter may result in premature air flow resulting in false failure. Rewetting is required in such case. 
- Test parameters may vary by change in wetting fluid due to change in surface tension of the liquids.


We provide automatic Bubble Point Tests for membrane filters cartridges and capsule filters. Such as Pall, Sartorius, Merck Millipore, Parker/ Domnick Hunter, 3M/ Cuno, Amazon etc. etc,…

In the upcoming blogs:
ABSTRACT OF INTEGRITY TESTS 3/3 – Diffusion Test (DFT) (Forward flow test)