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Penetrant Testing History

Written by Administrator
Sunday, 01 June 2008 15:21

By Pierre CHEMIN and Patrick DUBOSC

June 2008
Updated in December 2014


Penetrant Testing is a widely used method which allows for the detection of open and surface breaking discontinuities on: all metallic materials, numerous mineral materials (glass, ceramics) and, after satisfactory compatibility test, some organic materials.

The main advantage of this non destructive testing method lies in the fact that all these defects can be detected, with a total reliability, whatever are:
• Their direction.
• Their position on part.
• The size and the complexity of the part under test.

Penetrant Testing can be used almost anywhere, except under water, using few items.

It also allows to carry out the inspection, in automatic process lines controlled by programmable controllers, of large runs of components such as: blades, suspension arms, etc. and this at a lower cost.

Few methods offer such a flexibility and such a versatility.

Although ‘’Intellectual Guides’’ were able to announce the death of Penetrant Testing before the horizon of the year 2000, Penetrant Testing nevertheless stays alive and is the first method (after Visual Testing, however) which precedes all the other methods of Non Destructive Testing.

Now, it is not the fact of the fate. Along the years, Penetrant Testing always integrated the technological developments, both in chemistry and in physics, which came one after one.

It is interesting to finger out that Penetrant Testing is a global method. It means that it is possible to inspect a part in a single process with this method, when that cannot even be thought about with Ultrasonic or Eddy Current Testing.

Some points of thinking:

• Which other Non Destructive Testing method allows to detect, on the leading edge, on the trailing edge or on the christmas tree foot of tens of thousands of turbine blades (for aeroengines or gas turbines) checked every day in the world, the discontinuities of 1 micrometer of opening, 10/15 micrometers deep, 300 micrometers long ?

• Which other method may be used on titanium or ceramic prosthesis as well as on polyimide (a synthetic material used in some aircraft parts) parts, etc, to detect open to the surface discontinuities just for 20 to 30 cents per part ( excluding personnel costs)?

• Nanotechnologies have been a premium for some years. Penetrant Testing is a pioneer in this domain!! Indeed, a crack of the size mentioned for the turbine blades, is going to trap at best some tens of nanograms of fluorescent dye, that the "obsolete detection " system, that is the eye + human brain set (sensor + signal processing device), is going to detect in a fraction of second and interpret in some seconds. All this without electronics, without battery, without being connected to a computer!

Regrettably, a lot of people who do not know much about the requirements of Penetrant Testing, impose requirements which we cannot meet. A very current example: in refineries, one " forbids using flammable products ", wants "especially no aerosols propelled with flammable gases ". The Safety Service writes it as an essential requirement. When we come to carry out a red dye penetrant inspection, a volatile, nonhalogenated solvent cleaner, thus easily flammable or very flammable, will be needed. A developer having a volatile carrier, nonhalogenated thus easily flammable, will be needed; so that the applied coating is in accordance with the Penetrant Testing requirements, it is necessary to use a LIQUEFIED gas, nonhalogenated for metallurgical reasons; thus some butane-propane, extremely flammable.

The Penetrant Testing story is not thus ended!

Who, nowadays, knows best the history of Penetrant Testing ?

If this history appears in a certain number of works, it is always in an inaccurate or indistinct way and, mostly, incomplete.

What is the reason?

First of all, all the precursor developments were not recorded, because, in these times, means of distribution of knowledge and works were comparable in no way to today’s.

Many Engineers, who worked on Penetrant Testing, have passed away or left their job without recording any of these improvements

Pierre CHEMIN and Patrick DUBOSC, two physico-chemist Engineers, actively worked in Penetrant Testing since the end of the 60s. They noted all the developments until our days, while participating in it.

Indeed, throughout their professional career, they were in a privileged position, being at the interface between users and manufacturers of products, equipment and accessories and the users.

Actors, Trainers, Authors of numerous publications and Speakers, they were the best expertised to write the history of Penetrant Testing which you will find displayed, below, in a synoptic way, in tabular form.

Do not hesitate to contact us to give us of your comments and to ask for additional information.

Penetrant Colour Method of
penetrant application
Penetrant remover
Excess of penetrant
removal from the surface
Developer Method of developer application
1880-1920 “Oil and whiting technique” used for the inspection of railroad parts (axles and shafts) and boiler plates.
Before 1900 Vegetable oil
Animal oil
From 1915 Mineral oil Colourless By immersion Sand blasting Calcite whiting Powdering
Mid-1930s Research works by the Americans Carl Betz, Forster. B. Doane and Taber de Forest.
From 1940 Hand-held (UV-A) lamp fitted with a separate Woods glass filter.
October 14, 1941 The American Robert C. Switzer patents the fluorescent penetrant system. US patent N° 2,259,400.
June 1942 Water-washable Fluorescent By immersion Built-in Water Mineral powder made mainly of talc Dust storm cabinet
Late 1944-early 1945 The beginning of the wet developer technique.
March 26, 1949 The American Loy W. Sockman files the very first patent regarding the colour contrast penetrant which was later split to obtain two patents:
• US Patent N° 2,667,070, January 1, 1954, ‘‘Dye solution flaw inspection method’’, Loy W. Sockman and Elliot W. Brady, Assignee: Northrop Aircraft Inc.
• US Patent N° 2,764,556, September 09, 1956, ‘‘Dye solution flaw inspection composition’’ Loy W. Sockman and Elliot W. Brady, Assignee: Northrop Aircraft Inc.
Around the end of the ‘40s Mineral oil Colour contrast (blue, then red) By brushing, by immersion Sand blasting, sawdust and solvent White or yellow powder Powdering
August 16, 1949 The Americans John M. Stockely and George M. Cook patent the dual purpose penetrant. US patent N° 2,478,951.
From 1950 Spray can Spray can Spray can
1953 Post-emulsifiable Fluorescent Lipophilic Water
Before 1960 Cracked aluminium block/ASME Penetrant comparator.
By 1960 Chlorine and sulphur content measured in penetrant materials according to the ASME code requirement.
January 5, 1960 The Americans Joseph Switzer and Donald W. Parker, Jr. patent the penetrants with the cascading effect (excitation energy transfer). US patent N° 2,920,203.
Containing at least two dyes with excitation energy transfer (cascading effect) Fluorescent
April 3, 1962 The American Donald W. Parker Jr. patents the water-based penetrant. US patent N° 3,028,338.
From 1962 Water based penetrant (Compatible with liquid oxygen) Red dye and fluorescent Water Dry developer
October 15, 1963 The American James R. Alburger patents a method and an apparatus for determining the fluorescent penetrant sensitivity (using a meniscus technique). US patent N° 3,107,298.
From 1963 Automatic process line.
December 10, 1963 The American Joseph Switzer patents the self-developing penetrant technique. US patent N° 3,114,039.
1965 ? A British, probably an Engineer from Rolls-Royce Ltd, or Norman Henry Hyam invents the hydrophilic emulsifier.
October 24, 1967 The American James R. Alburger patents the gel-forming penetrant and emulsifier. US patent N° 3,349,041.
Jan 31, 1968 The British John Derek Hislop and Fred Dyson patent the foam application of the emulsifier. British Patent N° 1,101,552.
December 24, 1968 The Americans Adolf Mlot-Fijalkowski and Joseph A. Strosnik patent the LOX-compatible penetrant system. US patent N° 3, 418, 078.
(Penetrant mainly made of a polymer of cholorotrifluoroethylene - Developer being trichloroethylene-based)
From 1969 Waste water treatment on granular activated carbon.
1969 Electrostatic spraying application of penetrant materials
March 1969 The American E. O. Lomerson Jr. designs a two-fold congruence test for the quantitative evaluation of factors influencing the penetrant process sensitivity.
From 1970 Dual purpose, colour contrast, and fluorescent Halogen free propellant spray can Halogen free propellant spray can Halogen free propellant spray can
Peelable developer Spray can
November 3, 1970 The American James S. Borucki patents the water suspendable developer. US patent N° 3,538,016.
February 9, 1971 The American James S. Borucki patents the water soluble developer. US patent N° 3,561,262.
February 16, 1971 The American Orlando G. Molina patents the reverse penetrant testing technique. US patent N° 3,564,249.
Colour contrast Red Fluorescent
April 26, 1973 The British Norman Henry HYAM patents the thixotropic penetrant system. British patent N° 1,315,121.
Thixotropic Dual purpose: Red dye and fluorescent Brush Lipophilic
From 1973 High temperature penetrant Red dye Brush High temperature penetrant remover Brush or clean dry rags High temperature developer
Nickel Chrome test panels.
1975 The TAM panel complies with the Pratt and Whitney drawing TAM 146040.
October 28, 1975 The American Orlando G. Molina patents the so-called biodegradable penetrant system. US patent N° 3,915,885.
So-called biodegradable penetrant Red dye and fluorescent Immersion Built-in Water With or without developer
From 1978 Synthetic developer
From October 1978 Total halogens (chlorine, fluorine, then, subsequently, bromine) content and sulphur content checked in penetrant materials, according to the French nuclear RCC-M code requirements.
September 1979 Sidney Allinikov patents the encapsulated fluorescent penetrant. US patent N° 4,273,671.
By 1980 Combined digital radiometer/luxmeter.
1981 Heat fading resistant fluorescent penetrant
Single-use bakelite test panel.
From 1982 Special penetrant for carbon-fibre composites Fluorescent
May 5, 1982 Data acquisition system: Automated system for the detection of fluorescent indications under UV-A light by an automatic electronical and optical scanning system.
The inventors are the British Martin Edwin Allard and Joseph Augustine Willcox. European Patent N° 0,050,935.
September 28,1982 The American Vilma A. Garcia patents a high temperature penetrant testing system. US Patent N° 4,351,185.

Temperature ranges:

82-188 °C (180-370 °F) and 188-260 °C (370-500 °F)

Red dye or fluorescent Hot-melt marking crayons Excess penetrant remover Hot-melt marking crayons


Non-aqueous wet developer

Electrostatic spray gun.

Spray can

April 20, 1983 The French Jean Fernand Vaerman patents a device for the automatic reading of fluorescent PT indications. European patent N° 0,093,636. US patent N° 4,536,654.
1984 The French Jean Fernand Vaerman invents an automatic method for fluorescent penetrant process sensitivity measurement
November 1984 The American Michael Van Hoye patents a kind of felt tip pen to apply the fluorescent penetrant. US patent N° 4,621,193
From 1990 Spray cans with pouches
1992 Warning regarding health risks to the human health due to alkylphenol ethoxylates in penetrants and hydrophilic emulsifiers.
1995 Fan cooled hand-held (UV-A) lamp fitted with a separate Woods glass filter.
Ca 1997 KC-Coupon (or Kleen-Check Q Pon) to check the efficiency of degreasing prior to penetrant inspection.
1998 (UV-A) sources fitted with µ-xenon discharge bulb.
1999 Twin KDS (Known Defect Standard) panels.
From 2000 Penetrant pen Pen Cleaner-impregnated towels Developer pen Pen
AZO III A2 amine free colour contrast penetrant Spray can, airless spraying or Immersion
From 2005 Alkylphenol ethoxylates- free penetrant Alkylphenol ethoxylates- free hydrophilic penetrant remover
Low temperature penetrant (-30°C)
From 2004 (LED) Light-emitting diode (UV-A) sources.
From 2007 (LED) Light-emitting diode (blue light) sources.
Last Updated ( Friday, 15 May 2015 08:58 )