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Moisture Content - Water Activity – Are They the Same Thing?

Posted by Art Gatenby on Mar 6, 2012 4:19:00 PM

The other day, I woke up with a lingering quandary: Are the concepts of

Moisture Content and Water Activity the same thing?

As usual, I’ve decided to take on the task of clarifying the difference.  I hope I pull it off.

From the perspective of someone who supplies instruments that measure moisture content, water activity has not been a primary consideration.  However, I believe that comparison and contrast of these important concepts will be useful.

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Topics: Moisture Sorption Isotherm, Infrared Moisture, Moisture Analysis, Water Activity, Moisture Testing

Is Sieve Calibration Really the Holy Grail? Part II

Posted by Art Gatenby on Feb 7, 2012 4:44:00 PM

 Is Sieve Calibration Really the Holy Grail? Part II: Inside a Sieve Test 

As I start on this second installment of The Adventures of Pequeño: The 150 Micron Particle, I wonder why I get myself into these serial onslaughts. However, a promise is a promise, so I shall press on.

You will recall from Part I: Sieve Certification, our little friend Pequeño, a particle on a determined quest to make it through sieves -- particularly those through which he should be too large to pass. In this scenario, Pequeño along with some of his family and friends -- all small particles about 150 microns in size -- are on their way to a sieve test.

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Topics: Sieve Shakers, ASTM, Pequeño, Calibration, Particle Size Analysis, Sieve Calibration, Sieve Certification, Sieve Testing, Sieves

Which Type of Tensiometer do I Need?

Posted by Art Gatenby on Dec 22, 2011 6:55:00 PM

As followers of these rants know, Fisher Scientific stopped offering its Tensiomat Tensiometer about a year ago. As a tensiometer manufacturer, we at CSC Scientific were very interestedin this and have tried to let the world know that we might be able to help with things such as replacement rings, trade-ins and the like.
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Topics: Wilhelmy Plates, duNouy Rings, Tensiometer, Surface Tension Measurement, Surface Tension, Fisher Tensiomat, Tensiomat Trade-In

Who Beats Up Your Bostwick?

Posted by Art Gatenby on Nov 16, 2011 12:11:00 PM

Sometimes we encounter a product that is so simple and rugged that it would be tempting to deem it indestructible. Consider a stainless steel trough with a gate and etched numbers on the bottom. Seems simple and the stainless would make it tough, right? That is not the case, but it has survived nearly unchanged for more than 85 years.

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Topics: Bostwick Consistometer, Consistency

Is Sieve Calibration Really the Holy Grail? -- Part I: Certification

Posted by Art Gatenby on Nov 7, 2011 3:13:00 PM

Sieve calibration is the final step in determining whether processes yield suitable end results. In other words:
  • Is your concrete going to be strong enough?
  • Will you chocolates taste right?

  • Will your washing powder flow and dissolve as advertised?

  • Is there dangerous residue in your pill stock?

  • Will the “frack sand” keep the fractures open?

  • Is my salt of the correct grade?

If these are not correct, serious consequences could result (e.g. spoiled product, returned batches, rework or scrap).

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Topics: Calibration, Particle Size Analysis, Sieve Calibration, Sieve Certification, Sieve Testing, Sieves, Sieving Process

Why Do I Get Inconsistent Moisture Test Results?

Posted by Art Gatenby on Oct 14, 2011 2:32:00 PM

Why are my Moisture Test results inconsistent?” 

That is an issue for many of you who test for moisture. We discussed the complexities and multiplicity of issues involved with moisture content determination in our “Loss-on Drying Moisture Analysis and other Moisture Mysteries” series.

In addition to intrinsic properties of test samples that may adversely affect moisture testing systems, automatic equipment parameter set-up, operator oversights and sample handling contribute to seemingly intractable moisture test result inaccuracies.

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Topics: Moisture Analysis, Moisture Testing, Karl Fischer, Loss-On-Drying, Moisture

Why Calibrate a CSC DuNouy Tensiometer?

Posted by Art Gatenby on Sep 13, 2011 11:14:00 AM

Within the catalog of questions we are asked is a  category related to Calibrating duNouy Ring Tensiometers. The subject matter ranges from how, why and what is proven?

I guess the immediate and wise-assed answers are:

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Topics: duNouy Rings, Tensiometer, Surface Tension Measurement, Surface Tension, Calibration, Interfacial Tensiometer, Fisher Tensiomat

Karl Fischer Moisture – Answers to Questions We Get Asked

Posted by Art Gatenby on Jul 29, 2011 4:08:00 PM

When People are first introduced to the Karl Fischer Moisture Determination Method, eyes glaze over and we can perceive a mental “Why did I ask?

If you have any history with moisture analysis, you will have found, that for some applications, the Karl Fischer Titration Method is the best and sometimes the only way to get an accurate moisture measurement.

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Topics: Moisture Analysis, Karl Fischer, Karl Fischer Titration, karl fischer moisture, karl fischer moisture determination, karl fischer questions

Sieves – Old and New QC Issues

Posted by Art Gatenby on Jul 6, 2011 3:13:00 PM

In April, we published an article in "Powder-Bulk Solids" comparing certification process veracity with a sieve calibration process using calibrated glass microspheres (or beads). The certification process merely indicates that a sieve mesh conforms to a standard that has a wide tolerance regarding mesh openings. It is performed on a small number of openings. On the other hand, calibration using the calibrated beads results in a number representing the mean opening -- a result generated by actually performing a test encompassing at least 80% of the mesh openings.

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Topics: Sieve Shakers, Calibration, Particle Size Analysis, Sieve Calibration, Sieve Certification, Sieve Testing, Sieves, Sieving Process

Loss-on Drying and Other Moisture Mysteries - Part V: Drying

Posted by Art Gatenby on Jun 15, 2011 12:55:00 PM

Just over six months ago, I began this journey explaining the simplest approach to measuring or determining moisture: Loss-on Drying. Little did I know how involved and esoteric it would become.

This voyage has taken me down mysterious paths through spooky theories, back to age-old chemistry concepts and into the vagaries of thermodynamics related to evaporation, vapor pressure, bound water and water activity. I have come full-circle; back to explaining Loss-on Drying -- a form of drying that I had assumed would be the simplest of all.

I thought the first four topics [evaporation, vapor pressure, bound moisture, water activity] were tough, complex, confounding and less-than-obvious. Drying -- defined as “the mass-transfer process of removing water (or other solute) by evaporation from a solid, semi solid or liquid” -- seemed easy.

As is often the case, reality makes “easy” a non-operative word. Such has turned out to be so with respect to the issue of drying.

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Topics: Free Moisture, Moisture Sorption Isotherm, Moisture Analysis, Moisture Testing, Loss-On-Drying

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