Use of Method D Hydrophilic Emulsifier


Learn about the Method D liquid penetrant inspection nondestructive testing method, including basic steps for using a refractometer, preparing an emulsifier concentration chart, and determining hydrophilic emulsifier concentration

By Cheri Stockhausen, Product Application Manager 

Of the four available methods to remove surface penetrant during the fluorescent penetrant inspection process, the hydrophilic post emulsifiable penetrant process, Method D, is used when tighter control of the penetrant process is desired.

In the water washable penetrant process, Method A, it is critical to control the penetrant rinse time since water washable penetrant has the potential to be over washed. Decreased sensitivity and decreased brightness of penetrant indications may result from over removal of water washable penetrant.

The Method D hydrophilic post emulsifiable penetrant process offers tighter control of surface penetrant removal because the post emulsifiable penetrant is not removable with water alone. Hydrophilic emulsifier is necessary to remove excess penetrant from the test surface. The Method D penetrant process allows for tighter control of the penetrant removal step and improved sensitivity of the fluorescent penetrant process.

Techniques When Using Method D

Method D fluorescent penetrant inspection utilizes Hydrophilic Emulsifier to remove the surface penetrant. Hydrophilic Emulsifier is supplied as a concentrate by the manufacturer, and the hydrophilic emulsifier is diluted with water prior to use. The steps in the Method D penetrant process are penetrant application, penetrant dwell, water spray pre-rinse, immersion in the diluted hydrophilic emulsifier solution and then a water spray post rinse, followed by hot air drying, developer application, and inspection under UV light. The hydrophilic emulsifier is used at the concentration recommended by the manufacturer, typically 20% by volume for immersion applications.


Method D Process Chart

Verification of the hydrophilic emulsifier concentration is required at initial solution preparation; any time additions are made to the emulsifier solution and weekly as required by ASTM E1417 and industry specifications.

Water content may be determined by laboratory methods such as distillation or Karl Fischer titration. Subtracting the % water content from 100% will give the % concentration of hydrophilic emulsifier. If a laboratory apparatus for testing water content is readily available, this is a straightforward approach. However, often the lab equipment is not available, or the penetrant inspection department is unable to wait for the water content results before starting to process test parts.

An alternative to the measurement of water content in the laboratory is the measurement of refractive index. The refractive index of the hydrophilic emulsifier solution can be measured with a portable refractometer and then related to the concentration of the hydrophilic emulsifier. The refractive index can be measured in a few minutes in the penetrant inspection area. There is no need to take a sample to the lab and wait for results.

Refractometers measure the degree to which light changes direction. The change in direction of light will be different for different concentrations of emulsifier so the refractive index readings can be correlated to known concentrations of solution. It is important to note that the direct refractometer reading is not the solution concentration. The refractometer reading must be converted to the concentration of the hydrophilic emulsifier.


Refractometer Reading in Relation to the Hydrophilic Emulsifier Concentration

This can be accomplished by preparing known concentrations of hydrophilic emulsifier, measuring and recording refractometer readings of the known concentrations, and plotting a graph of the refractometer readings vs. known concentrations.

Prepare several known concentrations of hydrophilic emulsifier in water. For example, if hydrophilic emulsifier is used at 20% concentration, prepare known emulsifier concentrations of 5%, 10%, 15%, 20%, 25% and 30%.


Preparing the Known Concentration Samples

Supplies needed are unused hydrophilic emulsifier concentrate as supplied by manufacturer, graduated cylinder, and several beakers. Alternate method: volumetric pipets and volumetric flasks may be used in place of graduated cylinders and beakers.

For consistency, use the same source of water that will be used to prepare the hydrophilic emulsifier solution in the penetrant inspection line. For example, if tap water is used to prepare hydrophilic emulsifier solution in the penetrant inspection line, use tap water when preparing the known concentrations.

The same calibrated refractometer should be used to measure the known concentration samples as is used to test the hydrophilic emulsifier concentration at makeup and weekly.


Portable Refractometer

Preparing 100 ml of each known concentration will keep the calculations simple. Using a 100 ml graduated cylinder, prepare the 5% emulsifier solution by adding 5 ml of hydrophilic emulsifier to 95 ml of water for a total of 100 ml of 5% emulsifier solution. Adding the hydrophilic emulsifier to the water will facilitate the mixing of the solution. Pour the 5% emulsifier solution into a labeled beaker. Follow this procedure to prepare the remaining known emulsifier concentrations.


Known Concentrations of Hydrophilic Emulsifier


Graduated Cylinder

Measure and record the refractive index of each prepared emulsifier concentration using the same calibrated refractometer.


Preparing a Concentration Chart

Prepare a concentration chart by plotting the refractive index readings vs. the known concentrations. Draw a best fit line. This chart may be used to determine unknown concentrations simply by determining where the refractive index reading intercepts the best fit line and following down to the % concentration on the graph. The equation of the line could also be determined, and each refractive index reading could be plugged into the equation of the line to determine the concentration.

How to Utilize a Concentration Chart

Refractometer reading of 14 corresponds to 17% hydrophilic emulsifier concentration.

Once the concentration chart is prepared, refractive index readings are easily converted to % hydrophilic emulsifier concentration. If necessary, adjustments or additions are made to the emulsifier solution, and then the adjustment is confirmed with another refractive index measurement. Certain specifications require that a concentration chart is prepared each time that a new batch of hydrophilic emulsifier solution is prepared. Governing specifications should be reviewed to determine facility requirements for hydrophilic emulsifier concentration charts.


Want to see what Method D Hydrophilic Emulsifier and penetrants Magnaflux offer? Check out our ZR-10E​ Emulsifier and our Post Emulsifiable Fluorescent Penetrants.


Published October 23, 2018

Please wait while we gather your results.

Related Blog Posts

The Ultimate Guide to Fluorescent Penetrant Testing [Infographic]

The Ultimate Guide to Fluorescent Penetrant Testing [Infographic]

Liquid penetrant inspection is a nondestructive test method which does not harm the parts being inspected.


Dye Penetrant Infographic

The Ultimate Guide to Visible Dye Penetrant Testing [Infographic]

Some handy tips for beginners who are new to visible dye penetrant testing or NDT pros who want an easy reference guide.


AMS 2644 Penetrant Sensitivity Levels

A Guide to AMS 2644 Penetrant Sensitivity Levels

Understand fluorescent liquid penetrant sensitivity levels and how to find the right one for your application


Liquid penetrants for leak detection of ventilation systems

Using Fluorescent Penetrant for Ventilation System Leak Detention [Case Study]

Learn how to look at the recommended actions associated with the chemical risk assessment.


Protective Armor Inspection with Zyglo Penetrant [Case Study]

Protective Armor Inspection with Zyglo Penetrant [Case Study]

In this case study, we show how an armor solutions provider increased quality control on a semi-porous surface with ZL-19


Dye Penetrant Testing on Pipe

How Low Temperatures Impact Dye Penetrant Testing

Learn how lower inspection temperatures affect the performance of dye penetrant testing cleaners, penetrant and developers


5 Things to Consider When Choosing a Mag Particle Yoke [Checklist]

4 Habits of NDT Aerosol Safe Handling

Safety is a make-or-break factor in a technician's world – we list details around hazards, storage, recycling, and shipping of NDT aerosols


AMS 2644 Revision G: Key Changes and Updates

AMS 2644 Revision G: Key Changes and Updates

On April 8, 2019 AMS 2644G1 was published, replacing the 2013 revision F. This revision was completed as part of a standard review cycle, and to address changes in the industry and shortcomings of the previous revision.


Three steps to narrow down a penetrant method

Selecting A Dye Penetrant Method [Checklist]

Three steps to narrow down a penetrant method through governing specifications, part composition, and test parts


Penetrant Testing Demo

How to Do Fluorescent Liquid Penetrant Testing [Video]

Watch a demonstration of the penetrant inspection method according to ASTM E1417, including basic steps for NDT with an AMS 2644 Type 1 penetrant.


Magnaflux Dye Penetrant Testing

How to Do Visible Dye Penetrant Testing [Video]

Watch an overview of the dye penetrant testing method according to ASTM E1417, including basic steps for NDT with an AMS 2644 Type 2 penetrant.


Liquid Penetrant Aerosol Coverage Test

NDT Visible Liquid Penetrant Aerosol Coverage Test [Video]

See how three popular visible liquid penetrants perform in a coverage test to learn how many square feet each can covered


This technical paper shows examples of how Magnaflux can customize liquid penetrant equipment to me

Liquid Penetrant Equipment – Customized Solutions for Unique Needs [Video]

This technical paper shows examples of how Magnaflux can customize liquid penetrant equipment to meet part size and floor space requirements


Magnaflux Penetrant Testing

Exposing 10 Common Misunderstandings about Penetrant Testing

We reveal common misperceptions about liquid penetrant inspection we’ve seen in the field in recent years


Use of Method D Hydrophilic Emulsifier

Use of Method D Hydrophilic Emulsifier

Learn about the Method D liquid penetrant inspection nondestructive testing method


How Water Content Effects Viscosity of Fluorescent Penetrant

How Water Content Affects Viscosity of Fluorescent Penetrant [Case Study]

We show how a customer worked with the quality experts at Magnaflux to analyze data trends in the fluorescent penetrant to stay compliant


More Than Just Test Results, PeneCert™ Test Services is a Partnership

More Than Just Test Results, PeneCert™ Test Services is a Partnership

Liquid penetrant testing services help verify that your systems are compliant and act as a partner in your NDT process


NADCAP and Known Defect Standards

Understanding Nadcap System Performance Check and Known Defect Standards

Properly demonstrating the system performance check was the #2 Nadcap audit finding for penetrant systems. What do you need to do to comply?


Contaminated Powder Developer

9 Daily Performance Checks for Liquid Penetrant Inspection Systems

Learn more on why penetrant daily checks are important for the integrity of your LPI Systems


Understanding Safety Data Sheets

Understanding Safety Data Sheets: Do You Know What’s in the Chemicals You Handle?

We highlight the 5 major sections to understand on a Safety Data Sheets (SDS) in accordance with US OHSHA Hazcom 2012 GHS regulations


Learn about the available properties of developers

Does Developer Dry Time Impact Indication Strength?

Learn about the available properties of developers and the relationship between dwell time and inspection quality


Overview of Liquid Penetrant Inspection and Magnetic Particle Inspection Specifications

Overview of Liquid Penetrant Inspection and Magnetic Particle Inspection Specifications

Understanding ASTM and SAE/AMS specifications to select the corresponding Magnaflux product for Liquid Penetrant and Magnetic Particle Inspections


Benefits of Developer

Benefits of Using Developer During Liquid Penetrant Inspection [Case Study]

Learn how a automotive manufacturer increased indication detection in visible and UV light with developer.


Visible Liquid Penetrant Inspection

Better Weld Inspections with Dye Penetrant [Case Study]

Learn how one engineering and fab company improved their NDT weld inspection quality with SKL-WP2 dye penetrant.


Magnaflux Penetrant Inspection

Higher Sensitivity Penetrant Improves Inspection Quality [Case Study]

In this case study, we help an aerospace customer improve inspection quality and consistency with two Magnaflux penetrants


Magnetic Particle Crack Comparison

How Brightness and Contrast Impact NDT Inspections

How perception and vision can have a significant impact on probability of detection in non-destructive testing inspections.


Liquid Penetrant in Dip Tank

How to Maintain Penetrant Testing System Performance

Learn how liquid penetrant testing products lose performance over time and what to do to ensure penetrant test reliability.


PeneCert Test Services

Understanding PeneCert Test Services [SlideShare]

Learn more about test services for in-use penetrant, emulsifiers and developers to comply with ASMT E1417 and AMS 2644.


Magnaflux Penetrant Inspection

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

Learn the differences between type testing, batch testing and in-use testing for NDT liquid penetrants.



Leak Detection with Penetrant Testing Process

Read more about using penetrant testing products to inspect for leaks by using fluorescent or visible/colored penetrant to enhance visual detection of leaks.


Magnaflux Water Washable Penetrant

Water Washable versus Post Emulsifiable Penetrant – Which is Right for You?

Learn the differences between water-removable and non-water-washable liquid penetrant to figure out which is right for you


Subscribe to Magnaflux News:


155 Harlem Avenue
Glenview, IL 60025, USA
Telephone: +1 847-657-5300
Contact Magnaflux Customer Service

Select Your Country North America Mexico Brazil China Europe Russia India New Zealand, Australia, Japan, Southeast Asia
© 2019 Magnaflux - all rights reserved.

We have placed cookies on your computer to give you the best possible experience with our website. These cookies are also used to ensure we show you advertising that is relevant to you. If you continue without changing your settings, you are agreeing to our use of cookies to improve your user experience. You can click the cookie settings link on our website to change your cookie settings at any time.