Volume 5  Number 3                            Dennis R. Dinger                                1 January 2007

Updates

The E-zine

If this is the first issue of the Ceramic Processing E-zine that you've seen, you can add your name to the mailing list by clicking HERE.  All back issues can be accessed from the Publications page at the web site.  For those of you whose e-mail programs don't properly show the figures in these E-zines, go to the Publications page of the web site using your web browser to open any and all issues.  All figures should open properly when issues are accessed from the web site.  Questions, suggestions, and/or requests for topics to be covered in future issues of this e-zine can be sent to QuestionsandComments@DingerCeramics.com   .

If you have friends, business associates, etc., who are ceramists, materials engineers, or any other type of engineer or technician, and they are interested in receiving this e-zine, please forward this issue to them and encourage them to sign up.  Or simply point them to the Dinger Ceramics web site.  Also -- whether you are a new or continuing reader -- please send suggestions for topics you'd like to see addressed in future issues of this E-zine.

"... for Ceramists" Series Books

The paperback version of Characterization Techniques for Ceramists is available on the Books and Downloads page at the web site!    Retail price is $29.95 plus shipping and handling. The book has 256 pages and it covers 34 different characterization techniques that are commonly used by ceramists.  Order your copy NOW!

The book sets on the web site have also been revised to include this new book.  A 3-book set of paperbacks, including one each of Particle Calculations for Ceramists, Rheology for Ceramists, and Characterization Techniques for Ceramists, is now available for $64.85 plus shipping and handling.  This is a $10 saving off the total retail price of the 3 paperback books.  A 3-book set of downloads is also available for $52.85.  This, too, represents a $10 saving off the total retail price of the 3 downloadable books.  

The E-Book version of Characterization Techniques for Ceramists is available for downloading at the Books and Downloads page of the website for $24.95.  The download is a 2.889 Mb self-extracting Zip® file for the Windows® environment which unzips to the 2.998 Mb book in PDF file format.  Those of you who order the downloadable book will want to know that the PDF book is formatted to print on 5.5" X 8.5" paper (i.e., 8.5" X 11" sheets cut in half.)

The other two books, Rheology for Ceramists and Particle Calculations for Ceramists, continue to be available for purchase as downloadable E-books and as paperback books at the Books and Downloads page of the web site.

When You Find An Explanation, Is It the Most Fundamental Explanation?

Introduction

Have you heard of someone who always uses the same answer to solve a particular problem?  I am thinking of a ceramic engineer who rid one company of their casting problems by adjusting the level of flocculation of their slip to a higher concentration.  Then, several years later, having changed jobs to a different ceramics company with similar casting problems, he applied a similar flocculation adjustment to their slip.  Instead of eliminating their casting problems, however, their problems became dramatically worse.

The goal of this issue is to discuss the point that if a solution (and a particular line of reasoning) solves some problems, but exacerbates other 'identical' problems, the answer may not be completely wrong.  It may be that you just have not taken the reasoning to its simplest, most fundamental level.  There IS always a next, more fundamental level of explanation.  When you arrive at the correct, most fundamental level of explanation, it will either show the errors in your previous reasoning, or it will explain (and make perfect sense of) all of the seemingly contradictory results.  

Notice also that this line of reasoning applies to most subjects, both technical and otherwise.

Particle Size Distribution -- An Example

Although I wasn't talking about myself above, I can nevertheless use myself and my subject as an example.  If you have a ceramic processing problem and you ask me what is wrong, I might answer, "Your particle size distribution is bad."  I can (and do) use this answer frequently with many processing problems.  My answer needs to go further than this general one, however, to be useful.

In the event you asked yourself, "What would Dinger say?", and I'd give you the general answer, then your solution will depend upon your understanding of a 'bad' distribution.  If you think my idea of a 'bad' particle size distribution is a narrow distribution that doesn't pack well, you might interpret the solution to your problem to be, "You need to broaden your particle size distribution."

If I told you, "Your PSD is bad.", I would actually go into a lot more detail exactly how and why it is bad, and exactly how you should change it to fix it.  But for purposes of this discussion, we are assuming you are following only the most general answer.

In some cases, broadening a 'bad' particle size distribution to make it a 'good' distribution may help.  On the coal slurry project at Alfred University almost 30 years ago, we wanted the densest possible solids loadings in our slurries at the lowest possible viscosities.  In that case, broadening and smoothing out the particle size distributions of the coal was essential.

In other cases, however, broadening a particle size distribution hurts.  Take, for example, the situation considered in the previous issue of this e-zine.  In that example, the fired parts were rapidly moving out of the desired size specification because shrinkages were too low.  Their PSD was bad.  Their specific problem, however, was that their particle size distribution was too broad and it needed to be narrowed.  Their packing potential was too high, so they had to reduce that particle size distribution's capacity to pack.  In that case, they had to narrow the particle size distribution to solve their specific problem.

So if their engineer had assumed that their PSD was 'bad', and he had broadened it to help, he would have made the problem worse.  It isn't that "PSD is bad" is wrong -- it simply doesn't carry the required level of detail necessary to solve the problem.

Rheology -- Another Example

If you asked me how to solve any rheological problem, my answer would be, "Particle Size Distribution and/or Interparticle Chemistry."  That answer alone may not be helpful to anyone -- but it is fundamentally correct.  Changes to one of those two categories of adjustments will solve most rheological problems -- but what specific changes are needed?  You need that detailed information to make this a useful solution. 

Once again, I can give you many levels of detail concerning how PSD and chemistry can and should be altered to change rheological properties.  But for purposes of this discussion, we will again assume that you only have the most general solution: "PSD and/or Interparticle Chemistry."

If you think that all rheological problems are helped by improving the packing capability of a distribution and/or by increasing the level of flocculation of the body -- if that is what you understand by appropriate "Particle Size Distribution and/or Interparticle Chemistry" adjustments -- you will have a solution that works sometimes and doesn't work other times.  

This is important:  It is entirely possible that an engineer can go through most of his/her career using simple rules like this (PSD improvements mean improved packing capabilities and chemistry improvements mean more flocculation) to successfully solve all rheology problems. Murphy's Law, however, still applies.  It says that these solutions will work every time until you really need them to work -- that is, they will work every time until you have parlayed your successful solutions into a new level of responsibility in a new job at a new company.  If ever they won't work, that is when it will happen (as in the example in the Introduction above.)

The fact that the general solution doesn't always work doesn't mean that your understanding is totally faulty, but that you may not understand the phenomenon at the required, most fundamental level which will explain both cases.  

Flocculation -- A Third Example

Most ceramic engineers understand that calcium and magnesium ions will flocculate casting slips.  This is generally true.  But we show figures in our PPC textbook where initial additions of calcium and magnesium ions to slips causes deflocculation.  What is going on?  

The part that is missing from this is the concentration of flocculating ions present in a suspension.  In most cases, calcium and magnesium cations do indeed cause flocculation.  Viscosities increase as they are added.  But when concentrations of the cations in suspension are already particularly high, additions of more of them causes deflocculation.  Viscosities decrease.  

The idea -- that additions of these cations causes flocculation and viscosity increases -- is correct.  But depending on concentrations, too many flocculating cations will cause just the opposite to occur.  Suspensions will become deflocculated and viscosities will decrease. 

The similar phenomenon occurs for deflocculants.  Initial additions may cause viscosities to decrease, but excessive additions may cause viscosities to then increase again. 

The ideas -- that certain cations cause flocculation and associated viscosity increases and that certain other additives cause deflocculation and associated viscosity decreases -- are not fundamentally incorrect.  But these ideas must be amended to include suspension responses to high concentrations of these additives.  It is entirely possible that throughout an entire career, an engineer may never venture into the range of high concentrations of either flocculants or deflocculants to experience the opposite phenomena.  It is entirely possible that an engineer will never experience too much flocculant causing deflocculation or too much deflocculation causing flocculation. 

In such a case, an engineer can be convinced from his/her total career experience that flocculants ALWAYS cause flocculation and deflocculants ALWAYS cause deflocculation.  If they are fortunate, they will never experience the opposite cases.  But as mentioned above, Murphy's Law says they will experience the opposite effects when they are least prepared for it and when they most need things to go their way.  

Once again, these ideas are not totally incorrect.  They need to be modified, however, by the next more fundamental understanding of the phenomena.  This level will be found by understanding not just THAT flocculation/deflocculation occur, but HOW flocculation/deflocculation occur.  

800 Numbers -- A Fourth Example

I have used this example frequently in classes throughout the years.  It is a rather dumb example (or I was rather dumb for thinking it) -- but it makes the point clearly.  I used to think that all toll-free (800) telephone numbers were located in Texas.  The first four or five (800) numbers I ever encountered were for companies located in Texas.  So I drew that conclusion, and for years I believed I was calling Texas whenever I dialed an (800) area code.  Now I know differently.  

My answer was not completely wrong.  Lots of (800) numbers ARE in Texas.  Lots of them, however, are not, and I now have corrected my bad conclusion.

In this case, as in the previous flocculation/deflocculation example, the conclusion was based on too few cases to understand the full phenomenon properly.  Both were based on experience, but both were based on limited experiences.

When A Solution Only Works Sometimes -- The Logic MUST Be Taken To The Next, More Fundamental Level

In all four cases above, the conclusions are supported by limited data or limited thought.  Certainly, I didn't pay attention long enough to realize that (800) numbers could be located anywhere in the US.  I had a few early experiences from which I drew my conclusion -- and then I considered the question no further.  Ultimately one day, I was embarrassed when I stated my conclusion about (800) numbers.  Ultimately one day, the engineer realized that his slip adjustment solution didn't work.  Ultimately one day, the engineer realized that an improved PSD was not necessarily a broader, smoother PSD.  Ultimately one day, the engineer was surprised to learn that flocculants can also deflocculate.

In these examples, the answers are actually partially correct, but each needs to be carried to the next more fundamental to gain the more sufficient explanation.

To generalize this, take your understanding of any phenomenon to its ultimate finest level and apply your best logical thinking.  When your solution solves some of the problems and doesn't touch some of the problems, it doesn't necessarily mean that your understanding is all wrong.  It may only mean that you need to go to the next, deeper level of thinking and to the next, more fundamental level of explanation to correctly understand the phenomena that control the problem.

An Unexplainable Industrial Example -- Sulfate Contents in Casting Slips

Here's another good example on a subject that I admit I do not fully understand.

There exists a taboo for whiteware casting slips that requires sulfate contents in casting slips to be below a certain number of parts per million.  This may be a local taboo;  it may be an industry-wide taboo;  I don't know which.  I first learned of this taboo years ago regarding one of Jim Funk's consulting jobs.

Casting yields at a company had crashed and were low to non-existent.  Jim Funk was called in to correct the problem.  He determined that the sulfate ion levels in the casting slip were too low.  He raised them considerably.  Yields returned to acceptable levels -- the immediate catastrophe had been averted.  The chief engineer who had not been present when the problem occurred returned to the plant.  When he realized that the adjusted process now had sulfate levels considerably higher than before, and most noteworthy, they were then above the taboo level where "everybody knows you can't make successful product at those levels",  he lowered the sulfate concentrations to their earlier values, brought back the problem, and caused the bottom to fall out of the yields once again.  

WHY?  I asked this over and over again at the time, as well as over and over again ever since then.  No answers have been forthcoming.

Why do we control sulfate contents in casting slips?  The primary stated reason (as best I can tell) is that we want to measure the soluble Ca++ and Mg++ ion contents.  Remember Ca++ and Mg++ are flocculating cations.  In flocculated slips, when calcium and magnesium ions are functioning properly, their concentrations are not easily analyzed.  Since flocculation generally requires the additions of calcium and magnesium sulfates, we can relatively easily analyze sulfate contents in interparticle fluids.  Simply filter press some slip in a Baroid press, and analyze the filtrate for its sulfate content.  Easy!  Right??

What part do sulfate ions play in casting?  We don't know.  They are the means for putting the flocculating ions we want into the slip.  Add calcium sulfate; use the calcium ions; filter press the sulfate ions; analyze sulfate contents; etc.  This is only part of the story, however.  We don't really know the full extent to which sulfate ions affect the slip casting process.  

Back to the earlier question:  From where did the taboo come?  We don't know.  How much sulfate is present in the raw materials in a whiteware casting slip?  Some.  Exactly how much?  We don't know.  How much sulfate can actually be filter pressed from a whiteware casting slip?  We don't know.  Does all of the sulfate reside in the interparticle fluid?  We believe so.  Does it all leave the filter cake with the filtrate?  No.  Some stays behind in the interparticle fluid.

Yet how are the results of sulfate ion analyses used?  Filter press a slip, analyze the sulfate content of the filtrate, convert this into an assumed calcium and magnesium ion concentration, calculate how much more sulfate must be added to reach the desired Ca++ and Mg++ control levels, and add that much more sulfate (in its calcium or magnesium forms).  Do we actually want to use the sulfate ions?  No, we try to control soluble Ca++ and Mg++ ion contents by analyzing and controlling the sulfate ion contents.  Do we know exactly how the sulfate (or lack thereof) contributes to the casting process?  No.

We understand very little of this.  We have taboos that require sulfates to be in certain ranges for casting to proceed 'properly.'  We find some companies and some instances in which we can break the sulfate taboos and casting actually works well.  We find other companies where losses increase when we break the sulfate taboos.

The solution to this problem is at the next more fundamental level which I have not seen explained by anyone yet.  The fact that the taboo holds in some cases and doesn't hold in other cases means we don't understand the contributions of sulfate ions to the casting process.  We need to go one or two or three levels deeper in our understanding to uncover and explain these phenomena.  When we get to that level of understanding, we will be able to explain the reason for the taboo, why it works sometimes, and why it doesn't work other times.

Is our understanding of this phenomenon all wrong?  No.  Is it at the required fundamental for true understanding?  No.  Not yet.

Conclusion

This requirement to look for the appropriate, fundamental level of explanation applies to any and all phenomena that we don't quite understand:

Sometimes, we find someone who understands and can explain phenomena at the next lower, more fundamental level.  In such cases, we are fortunate because we can expand our understanding of how and why certain things happen just by learning from that individual.

Sometimes, based on current understanding, we hope that making certain adjustments will correct the problem and make things work properly.  Sometimes the adjustments work, and sometimes they don't.

Sometimes, we find good explanations in the literature that advance our understanding of important phenomena.

Sometimes we are simply stuck with our lack of understanding of a phenomenon.  In this case, we make note that we need to find the next more fundamental level of explanation of the phenomenon that will explain all possibilities.  We don't throw out our whole understanding, but we keep our eyes open to find that next, more fundamental level of explanation.