Author Archives: metlchek

Water Content: Karl Fisher versus ASTM D95

We are getting phone calls asking why we do not use ASTM D 95 to measure the water content of penetrants and emulsifiers. ASTM E 1417 & NADCAP PRI AC7114/1 revision A, allow the use of ASTM D 95 or the modified Karl Fischer method. This latter method was introduced...

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More About Emulsifiers and Charts

In our last issue, we pointed out that some auditors now require that the user make his or her own concentration chart for our E-58D hydrophilic emulsifier. The apparent reasoning behind this is that there is no guarantee that the refractometer used by Met-L-Chek and the refractometer in the user’s...

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Water Pre-rinse

ASTM E-1417 states (Paragraph 7.3.4.2) that “Hydrophilic post emulsifiable penetrant shall be removed with a water Pre-rinse, application of the hydrophilic emulsifier and then a post-rinse.” There is an unanswered question as to whether this applies equally to both immersion in the emulsifier and to emulsifier that is sprayed on....

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What Do The Numbers On The Bottom Of The Can Mean

What Do the Numbers Mean We often get calls asking what the numbers mean on the bottom of the aerosol cans and how do they relate to our certification for the product. The first set of numbers is the canning or packaging date when the aerosol was filled. The next...

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More Thoughts on POD’s and Penetrant Inspection

Our recent article about penetrant POD brought this response from Brian MacCracken, now retired, but an important figure in the penetrant using community: “I enjoyed this month’s Pen Prof, as I usually do. However, I would like to add my two cents about POD’s for FPI and if you want...

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Shelf Life vs Tank Life

We frequently get questions concerning the shelf life of our products. Shelf life is a term that can be defined differently by different manufacturers, and we explain what is the practice for Met-L-Chek. This information is also contained in the literature on the Met-L-Chek web site. Met-L-Chek Company defines shelf...

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Penetrant Viscosity

Penetrant Viscosity It is easy for some of us to speak about “old times” in the penetrant business. In the early days, which implies something like 30 or 40 or 50 years ago, one of the requirements of the QPL was to list the penetrant viscosity. Certificates ofcompliance with the...

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Surface Roughness

We get a wide range of questions, from the sublime to the ridiculous. But we always understand that the question, no matter how “far out” it might seem, is an important one for the person who has asked it, andwe treat it that way. Our days are livened by some...

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Hydrophilic Emulsifier

Hydrophilic Emulsifier We probably do not say enough times that the subjects that are addressed in this publication originate with those folks who use penetrants. The last issue featured information about hydrophylic emulsifiers, and as usual, we received comments on the article. We relish receiving comments, because they come from...

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Understanding, Shades of Meaning, and Complete Obfuscation

We who work with specifications, such as ASTM E-1417, E-165, and the like are constantly reminded that it is important to be very clear. It needs to be clear to the person using the specification and it needs to be equally clear to anyone auditing the procedures. If the person...

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