Understanding Type-, Batch- and In-Use-Testing for Liquid Penetrants [Case Study]


In this case study, we help a manufacturing customer understand the differences between three types of testing for liquid penetrants

October 3, 2017

Penetrant Type Testing


The Customer

Our customer is a global manufacturing company that specializes in the inspection of components for the aerospace and defense sectors. Their work requires the use of high sensitivity penetrants in compliance with the specification requirements outlined in AMS 2644.


The Challenge

Our customer received a request for two requirements from their downstream customer:

  • Physicochemical parameters: immersion penetrant must be checked at least quarterly in accordance with AMS 2644 (acceptance tests).
  • For re-used penetrant and re-used emulsifier (when performed by immersion), it must be checked at least annually to make sure the physical properties are still in accordance with AMS 2644 sub-chapter 3.3.


Our customer was familiar with in-use testing of penetrants and were confused by this request since they did not feel that:

  • The acceptance tests should fall into their remit.
  • AMS 2644 Section 3.3 applied to them.


The Solution

The key point is to understand the differences between type testing, batch testing and in-use testing:

Type Testing

When seeking approval for a penetrant in accordance with material specifications such as AMS 2644 and EN ISO 3452-2, the penetrant manufacturer is responsible for getting the product type-tested. This involves sending a sample of the penetrant off to an independent laboratory for verification against a comprehensive set of standard tests. These tests are referred to as the ‘qualification tests’.

Batch Testing

During the routine manufacture of a penetrant and its associated consumable products, it is a requirement under material specifications such as AMS 2644 and EN ISO 3452-2 for the manufacturer to carry out several batch-specific tests.

These specifications also specify the sampling rate and dictate that results should be published on a certificate of conformance. These tests are referred to as the ‘acceptance tests’. Under AMS 2644, the acceptance tests are as follows (see table below):

Product Type Test AMS 2644 Reference
Penetrant Flash point 3.3.3
Viscosity 3.3.4
Fluorescent brightness (Type 1 systems only)
Water tolerance (Method A only)
Emulsifier Flash point 3.3.3
Viscosity 3.3.4
Water content (Method D only)
Developer Developer fluorescence
Developer removability
Redispersibility (Forms c, d and e only)

In-Use Testing

There is no reference for in-use tests within the AMS or EN-ISO standards. When a penetrant is used by a company carrying out inspection, they need to carry out a set of in-use tests. ASTM E1417 established standards for performance checks for in-use materials (see table below).

You can find more information on these tests here. You will also find details about our PeneCert™ testing service, where in-use tests are carried out using an independent laboratory.

In-Use Test Frequency
System performance Daily
Penetrant contamination Daily
Developer contamination (soluble and suspendable) Daily
Developer concentration (soluble and suspendable) Weekly
Developer condition – dry powder Daily
Water content (water washable only) Monthly
Emulsifier concentration (hydrophilic Only) Weekly
Penetrant sensitivity As required by 7.8.3
Fluorescent brightness – measured brightness Quarterly
Emulsifier water content (lipophilic only) Monthly
Penetrant removability (water washable only) As required per 7.8.3
Emulsifier removability (lipophilic and hydrophilic) As required per 7.8.3


The Results

The above information was relayed to the downstream customer, clarifying where testing responsibilities lie. Magnaflux is always willing to help our customers answer important questions such as this one.

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