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Chris Campbell

Troubles With Curves

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Every aspect of pottery has a learning curve to it ... sometimes we pick the knowledge up quickly and life is good ... and other skills take longer and more difficult to get.

 

For me, color, decoration and texture have always been fun and easy to figure out.

Throwing, I was probably average ... glaze enjoyment - below par ... firing - an ongoing learning curve.

 

BUT ... 'flocculation' and 'deflocculation' have always been confusing. Every time I have to sit and think it out. Yes, I know the trick of "flock of sheep gather together" etc, but then I have to translate that pearl of wisdom to the slip or glaze in front of me. Thanks goodness for Vince Pitelka's Studio Potter book ... my copy probably falls open to that page.

 

How about YOU? What are your slow and fast learning curves?

 

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I think different types of learning curves is partly driven by your individual personality or temperament, for which there are numerous online tests to assess yourself.  People typically say, "well of course that's what I'm like."  http://www.google.com/search?q=temperament+test

 

I like episodes of learning with a resolution.  I prefer a half-hour show to a movie.  Becoming ever better through steady practice, such as golf or throwing on a pottery wheel, is not appealing to me beyond the initial introductory phase and understanding the concepts involved  - like powering your golf swing with your abdominal muscles rather than your arms.  It was interesting and then it wasn't.  I can admire and purchase the work which has resulted from decades of relentless practice, but I know enough about myself to know I won't be the one making it.

 

After sculpting something, I'm sure I could do far better a second time, but it's not in me to do it - not without a long passage of time.

 

My partner likes the day to day running of our ceramic studio, while I like solving the problems or trying out new techniques.

 

My Mother has always told us to be grateful that not everyone likes what we like, otherwise there might not be enough for us.

Every aspect of pottery has a learning curve to it ... sometimes we pick the knowledge up quickly and life is good ... and other skills take longer and more difficult to get.

 

For me, color, decoration and texture have always been fun and easy to figure out.

Throwing, I was probably average ... glaze enjoyment - below par ... firing - an ongoing learning curve.

 

BUT ... 'flocculation' and 'deflocculation' have always been confusing. Every time I have to sit and think it out. Yes, I know the trick of "flock of sheep gather together" etc, but then I have to translate that pearl of wisdom to the slip or glaze in front of me. Thanks goodness for Vince Pitelka's Studio Potter book ... my copy probably falls open to that page.

 

How about YOU? What are your slow and fast learning curves?

 

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There is an old adage, "The good is the enemy of the best".  From that, I take an humble stand that there is always room for improvement, regardless of how 'good' I may think I am at whatever aspect of clay art involved.

I have been wheel throwing (off-and-on) for over 40 years now and still remember how 'good' it felt to be confident centering clay, how 'good' it felt to pull cylinders with even walls, how 'good' it felt to get a lid to fit, how 'good' it felt to have a teapot spout pour without dripping... but the more that I saw of the work of others, there always seems to be new/different/better ways to do ALL of these aspects of wheel-throwing. And not only 'better' approaches for a single function, but complex combinations and permutations of each aspect of wheel-throwing.  Still though, I measure my personal best with work from artists I admire just to remind me that learning in this art should never end...and to keep that learning curve moving upward (even gradually) takes commitment, energy, community, and a positive attitude.

 

Good grief that sounded like a sermon...'sorry.

Stepping down from the podium,

Paul B)

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Floc and defloc also confuse me every time. Maybe I should draw a picture and hang it on the wall. The whole science part of pottery, especially chemistry, is such a challenge. After continuously reading about it for three years, I am starting to get the hang of it, but it will never come easily. I still have to consciously tell my brain not to check out as soon as it sees a chemical formula in a line of text.

 

I have discovered I love handbuilding even more than throwing. It fuels a creative energy that keeps me working long hours and pushes me to try new things. Even if a piece does not work out, the pleasure of creating it makes the process worthwhile.

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I guess another part of this curve is that the unknown expands in some proportion with the known ... Or as more famously said, the more you know the more you don't know.

I'm in such a small subset of the pottery world ... Colored clay ... yet I am constantly challenged and amazed at how vast the unknown areas are. It seems as though I have barely scratched the surface of possibilities ... I haven't even begun my long desired goal of testing various minerals and chemicals along with the stains ... which I want to do but always slips by since I tend to chase shiny objects.

I'm sure it's similar to the humble mug ... You think you make a decent one until you pick up someone else's and are blown away by some aspect of it you had not considered.

We won't even get started on the thousands of years long road to the perfect tea bowl eh John?

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Flocculate and deflocculate - me too! And I thought it was because I was a novice, so reassuring to find others similarly challenged. So....when my glaze settles out with a thick layer at the bottom of the bucket it is ????????? and needs to be ??????????? with ??????? (Epsom salts? Dispex? Something else?)

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Learning curves are tough. I have always had a problem with glaze formulas, but understand the ingredients well. Skill development seems to be pretty easy, I push until I am satisfied-which seems to be never! :) I like to challenge myself with different types of forms when throwing or handbuilding. I usually take a long time figuring out how to make something, and then do it in a trial piece first, then do the final pieces.

 

I used to have to teach a lot of computer programs, and got to be pretty good at picking up new ones. I think in the end a glaze program will be my next learning curve. Presently I keep my glazes in a spreadsheet for ease of figuring amounts.

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I keep my glazes in an Excel sheet as well.  I use Insight (glaze program) to check COE problems, but when I'm trying to substitute ingredients I find it more understandable to use a messy sheet labelled atomic with a row for each ingredient I can copy and paste down where the chemical breakdown is in each column.  With the glaze programs I've seen, these are all hidden making it like a Black Box.  With the spreadsheet it's easy look over the sheet and see, say, where the excess Iron is coming from and what I'll have to substitute to home in on what I want.  That's an INTJ personality.

I used to have to teach a lot of computer programs, and got to be pretty good at picking up new ones. I think in the end a glaze program will be my next learning curve. Presently I keep my glazes in a spreadsheet for ease of figuring amounts.

 

I agree that most frequently the more you know about something the more you realize what you don't know.  But rarely do you find all those unknowns in one place.  I realized I was uncertain about that stability or reversibility of Cristabolite when High Bridge Pottery asked about quartz, so I had to find a reference to be certain of what I was saying.  But the reference site is so exhaustive it contains far more information about Silica crystallization forms than I ever hope to know.  But I bet if I learned it all, it would just leave me with new questions.

I guess another part of this curve is that the unknown expands in some proportion with the known ... Or as more famously said, the more you know the more you don't know.

 

I had to print out these two sentences as a reference for myself so I could keep remembering what flocculation and deflocculation were in the studio - and I wrote them, but had to print them out otherwise initially I'd get lost.

 

A.)  Add Magnesium Mg++ (Epsom Salts aka Magnesium Sulfate) and/or Calcium Ca++ (Calcium Chloride) and/or Hydrogen H+ (Acid) to allow a glaze to hold more water = flocculation.

 

B.)  Add Dispex (Darvan) or Sodium Silicate to remove the Mg++ and Ca++, (or a caustic to remove the H+) by locking them up in insoluble form, and the glaze settles to hold less water = defloculation.  Pour off the excess water which contains the Sodium which the Dispex or Sodium Silicate swapped for the Mg++ / Ca++ / H+.  But give it time to settle out to see where you are. 

 

If you did go far in step B, simply go back to step A and add more Mg++ Ca++ or H+.

 

****************

P.S.:  I've found explanations of "clay particles attracting each other because they both have charges" very unhelpful if you think too far.  For example when you add Mg++ you're also adding an SO4-- so why don't they cancel out.  This model breaks down because it gets too complex, because not all positive or negative ions have the same effects on the spacing of these particles etc. because of their geometry etc.- so not very helpful at all.  Keeping it  step A and step B is helpful.

Flocculate and deflocculate - me too! And I thought it was because I was a novice, so reassuring to find others similarly challenged. So....when my glaze settles out with a thick layer at the bottom of the bucket it is ????????? and needs to be ??????????? with ??????? (Epsom salts? Dispex? Something else?)

 

My partner has me focused on "just making stuff", rather than thinking out a complex hand-building project with prototypes, to try to keep me more social and fun at the studio.  Imagine that.

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I had to print out these two sentences as a reference for myself so I could keep remembering what flocculation and deflocculation were in the studio - and I wrote them, but had to print them out otherwise initially I'd get lost.

 

A.)  Add Magnesium Mg++ (Epsom Salts aka Magnesium Sulfate) and/or Calcium Ca++ (Calcium Chloride) and/or Hydrogen H+ (Acid) to allow a glaze to hold more water = flocculation.

 

B.)  Add Dispex (Darvan) or Sodium Silicate to remove the Mg++ and Ca++, (or a caustic to remove the H+) by locking them up in insoluble form, and the glaze settles to hold less water = defloculation.  Pour off the excess water which contains the Sodium which the Dispex or Sodium Silicate swapped for the Mg++ / Ca++ / H+.  But give it time to settle out to see where you are. 

 

If you did go far in step B, simply go back to step A and add more Mg++ Ca++ or H+.

 

****************

 

 

My partner has me focused on "just making stuff", rather than thinking out a complex hand-building project with prototypes, to try to keep me more social and fun at the studio Imagine that.

Thanks Norm: nicked, copied, pasted and printed. I'll stick it on the wall tomorrow if it's stops raining and the new lake between the house and garage has dropped a little.

 

I can!  :D

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I'm sure a lot of this would be intuitive if we saw these microscopic reactions happening, but we don't.

 

That's why I find these electron micrograph "photos" of clay particles stacking, and what not, very helpful because I can finally see what's happening.

 

The very sad part of all this is I don't really enjoy chemistry or physics - I studied it so I understand it and can tolerate it.  Unfortunately there's far too much of both in ceramics.

 

SLIP

When bonding two pieces of clay or when you apply slip to clay, if they don't both have the same amount of water the join can crack or fail in other ways.  So people spray acid (or epson salts or calcium chloride) on the clay to open it up to water, as the slip is already.

 

That's why I use add Pat Horesley's Score No More to the clay I'm using -  he already figured out a pretty good chemistry.

 

Pat Horesley's Score No More

100.0%  Dry Clay - the type you're using  == I just add the following ingredients to the wet clay I'm using

   2.0%   Feldspar Custer Potash

   2.0%   Bentonite

   2.0%   Gum Arabic

   0.5%   Darvan

 

It has flux (Feldspar) to help melt these joins together in the kiln.  The bentonite not only suspends, but also shrinks as it drys pulling the joins together more tightly.  I suspect the Gum Arabic gives the greenware more dry strength.  The Darvan is reducing the amount of water needed to make slip so it's drier and more closely matches the water level in the clay.  Darvan, being a polymer, also acts as a dispersant making the Horsely ingredients easier to mix with the clay.

 

This is less important with high grog clays or paper clay, but with high-clay clay bodies this combination does stuff you wouldn't believe.  Adding both Bentonite and Darvan seems to be in conflict, having opposite actions in flocculation/deflocculation, but this combination is magical.

 

Ok Norm ... So translate floc/defloc to an easy to remember formula when working with slip ... so you can apply it to surfaces without it cracking as it dries .... I can never remember which I am supposed to do! Neither choice seems intuitive to me.

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Ok Norm ... So translate floc/defloc to an easy to remember formula when working with slip ... so you can apply it to surfaces without it cracking as it dries .... I can never remember which I am supposed to do! Neither choice seems intuitive to me.

Sodium silicate does it for me, fluid slip without as much water as would normally be required for such fluidity, so ok for leatherhard ware which has already lost an amount of water.

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Adding a deflocculant (like Sodium Silicate) to the slip is one of the concepts in "Pat Horesley's Score No More" in the post above. 

 

Darvan costs more than Sodium Silicate but being a polymer, Darvan also acts as a dispersant - making it easier to mix the "Score No More" ingredients with the clay you're using.  On the other hand, the sodium in the sodium silicate is a flux working in the kiln like the feldspar in "Score No More".

 

I'll try out mixing sodium silicate with clay to make the slip to see how it compares to "Score No More".

 

Ok Norm ... So translate floc/defloc to an easy to remember formula when working with slip ... so you can apply it to surfaces without it cracking as it dries .... I can never remember which I am supposed to do! Neither choice seems intuitive to me.

Sodium silicate does it for me, fluid slip without as much water as would normally be required for such fluidity, so ok for leatherhard ware which has already lost an amount of water.

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Sorry, I thought Chris was writing of applying slip to her clay as opposed to joining clay with slip.  Other deflocculants with different chemical properties can be used. Sodium Carb?? Haven't used anything other than sodium silicate for a while. Works forget the rest, in my brain.

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Yes Babs, i was talking about decorating with slips since I never have much trouble attaching with slips of the same clay body.

I have LOTS of Darvan ... why, I dunno. Just have this large container of it.

But sometimes when decorating with slips they crack or just fall off the work.

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I've noticed that there can be bonding problems applying slip or under-glaze to clay whose surface has been worked so much as to be effectively burnished to a degree.  A similar surface can occur where the very exterior layer of the clay has dried too quickly.

 

I think the solution to that can be two-fold:

 

1.)  First applying a deflocculant like acid/Calcium Chloride/Epsom Salt solution to the clay - to chemically break open the clay surface again;

 

2.)  The addition of the Gum Arabic in "Score No More" or White Glue (PVA) to the slip.  Either provides a non-clay bond in areas where the layers of clay might otherwise shear.  I suspect the bentonite in "Score No More" can also fix "clay stacking" problems by acting as a filler in places where there are gaps between particles.
 

Not having met Pat Horsely I have no idea how he came upon the combining the four ingredients, but I'm impressed. 

He has other recipes for covering slips he uses.  http://www.patrickhorsley.com/glazes.html

 

How does that fit what you've experienced?

Yes Babs, i was talking about decorating with slips since I never have much trouble attaching with slips of the same clay body.

I have LOTS of Darvan ... why, I dunno. Just have this large container of it.

But sometimes when decorating with slips they crack or just fall off the work.

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Chris, Don't know what Darvan is! So the slips you are decorating with are of a different clay body? I use a porcelanous,spell??, slip on terracotta with Sod. Silic. as the only deflocculent. If I let my pot get too dry, it doesn't crack off but on bisquing may bloat away from bowl, usually on the inside. I do wet the soft leatherhard  T/C prior to slipping but this is commonplace stuff.

Maybe you need to use two different deflocs, with different chemical actions...Sod. Carb and Sod Silicate. Something about thixotropy

Sounds like you are using your usual fluidity but with some colours, it's cracking off at that fluidity, loaded with less clay particles and more water than you think??

Is this logical anyone?

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The only places I know of which use Darvan in large quantities are water treatment plants.  As with Xanthan Gum, you use very small quantities of these engineered products.

 

This is the tank where the Southern California Metropolitan Water District mixes Darvan with water pumped-in from the Colorado River.  Any clays or other particles in the water attach to the Darvan and are filtered out by sand beds.

 

Darvan Mixing Tank in Los Angeles

med_gallery_18533_676_563654.jpg

 

Darvan flocs being filtered-out with sand beds.

med_gallery_18533_676_894685.jpg

 

Some of our ceramic studio members checking out Colorado River water at the Parker Dam in Arizona from where it gets pumped to the Darvan Mixing Tank 275 miles away in Los Angeles.  A huge infrastructure and some fancy water chemistry supports our city in the desert.

med_gallery_18533_676_54825.jpg

 

Chris, Darvan has a shelf life of two years. Which means a lot of us have bottles supposedly useless Darvan. If you want more, I can drop mine off next time I am in the Raleigh area.

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Sounds right Babs ... So, a slip with less clay and more water needs to be flocculated?? ... Or de-flocculated?

 

Think of it this way:

Flocculate- to flock together like birds, or become thicker.

Deflocculate- to break apart a flock, or become thinner.

 

So we flocculate glazes so they don't settle out, and deflocculate slips to make them thinner without adding water.

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Words can be used to create so much misdirection.

 

A flocculated glaze feels and looks thicker, yet the same flock of clay particles are spread out over a much larger area of water, so the glaze is actually thinner, placing less glaze on ware with each dip.  So a thick glaze is actually thin.

 

Darvan is said to:

 

Deflocculate clay particles into a concentrated casting slip by removing water  .  .  .

and

Flocculate clay particles into floating lumps of plastic and clay in a water treatment plant so the water is clarified by removing clay and Darvan.

 

Is Darvan a clay flocculant or clay deflocculant.

 

Just like the words "clay plasticity" unless there's clear agreement and understanding of what the words mean, the same words can be used to describe seemingly completely opposite properties.  Darvan interact exactly the same in each situation, yet one Darvan is a flocculant and in the other Darvan is a deflocculant.

 

 

Sounds right Babs ... So, a slip with less clay and more water needs to be flocculated?? ... Or de-flocculated?

 

Flocculate- to flock together like birds, or become thicker.

Deflocculate- to break apart a flock, or become thinner.

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Sounds like Darvan is having an identity crisis! We have always used it as a deflocculant in slips. However if you add too much deflocculant to a slip, it will thicken up all nasty, like when chocolate siezes up. So maybe in higher concentrations it does the clumping in the water treatment plant.

 

Yes, technically a flocculated glaze would put less glaze per dip, but functionally I have not found it to be an issue. It's not thickening the glaze to the degree that a significant amount of water has to be added to get it to the proper fluidity for dipping. We use the same 6 count dip whether a glaze is deflocculated or not.

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