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b-mix -- cracks and inconsistencies

updated sat 11 aug 01

 

Jon Pacini on thu 9 aug 01


Greetings all---------OK, I'll take the bull by the horns-----I get a couple
of categories of complaints regarding B-mix. Greenware cracks and
inconsistencies in firmness and/or composition.
Let's start with the greenware cracks.
B-mix is extremely plastic. It's plastics to non-plastics ratio is what
makes it so easy to throw and so popular. Shrinkage accompanies plasticity,
it is the underlying cause of cracking at this point in the process. If you
get unevenness of drying with B-mix you stand a good chance of having a
failure do to uneven shrinkage and cracking. Rims that dry before the
bottoms will split or s-crack up from the bottoms. Handles and spouts if
they are not the same consistency when added or if they dry unevenly will
crack or pop-off. When you use B-mix you better pay attention to the drying.
Potters send me bags of B-mix and tell me it cracks every time, I
believe them. The first thing I do is an X-ray diffraction analysis of the
sample they send in. This gives me the mineral composition and percentage, I
compare it to a lab standard we keep.
If that looks bad, I recommend replacement and then I try to find out
what went wrong.
If that looks good, I take that bag of clay over to the wheel or slab
roller or extruder and put it through it's paces. I've had enough experience
with clay to know I can't mimic their technique exactly but I try to get a
handle on it from talking to them and then do my best. Usually I try to get
an example of the failure out of them. That helps out tremendously by the
way. If I get the same failures they're getting, I try to figure out why.
If it's technique, I try to find a way around the offending technique
and still end up with the same finished product.
If the technique is inappropriate to the body, I try to talk them into
trying a different body. Hopefully without sounding like a paid spokesman,
for example Dave's Porcelain uses the same minerals in a more traditional
combination.
Many times I find potters who are on the edge of having failures, that
is "sometimes it works, sometimes it doesn't". They want to blame it on
inconsistencies in the clay, but usually it is an inappropriate clay choice.
The clay just isn't suited to their particular way of working. B-mix can be
very unforgiving if you expect it to handle like a traditionally formulated
body.

Variations in formulation is a non-issue. B-mix, as Laguna has made it,
has not changed in materials used or percentage used since it's inception in
1985. Contrary to popular belief, wholesale substituting of minerals does
not take place.

Inconsistencies in firmness/softness is a continual struggle. We keep
logs of all minerals used and their weights, water used. What we call
"pentrometer readings' are taken at the mixer and the pug mill. Timers
control the mixing process. My crew chiefs have an average of 15yrs
experience, none has less than 5. I look over the log books and spot check
the clay personally. We will make a minimum of 40 batches of B-mix at a time
and try to be as consistent as our tools and equipment will allow. Everyone
has someone else on hand to double check every step and procedure. When the
clay is made, it's done right.
When B-mix sits, it firms up. We've tried to address this issue by
pugging the clay at a slightly softer pentrometer reading. We rotate the
stock so that hopefully nothing sits here for months and our production
level is such that we make it nearly on a weekly basis.
If you get soft B-mix, it more that likely was just made. If your B-mix
is firm, it may be a month old. If you purchase from a distributor your clay
may be several months old, depending on how often they order the clay.
Every 2000lbs of clay has a batch number and can be tracked. I can tell
you who what when and where.
If you request a softer or firmer ton of clay, we will make it.
If you want a modified ton of clay, we will make it. We make over 2000
special formulations. If you called me today with your personal formula I
would give it #2957.
I hope that Rant resolves some questions.
Sorry if I sound like a paid spokesman--------again-------

Jon Pacini
Clay Manager
Laguna Clay Co

Gayle Bair on fri 10 aug 01


Jon,
Thank you for your bravery in the line of fire!
I am currently using B-mix after a hiatus of 2 years and do enjoy it's
plasticity.
You mentioned:
"If that looks bad, I recommend replacement and then I try to find out
what went wrong.
If that looks good, I take that bag of clay over to the wheel or slab
roller or extruder and put it through it's paces. I've had enough experience
with clay to know I can't mimic their technique exactly but I try to get a
handle on it from talking to them and then do my best. Usually I try to get
an example of the failure out of them. That helps out tremendously by the
way. If I get the same failures they're getting, I try to figure out why.
If it's technique, I try to find a way around the offending technique
and still end up with the same finished product.
If the technique is inappropriate to the body, I try to talk them into
trying a different body. Hopefully without sounding like a paid spokesman,
for example Dave's Porcelain uses the same minerals in a more traditional
combination.
Many times I find potters who are on the edge of having failures, that
is "sometimes it works, sometimes it doesn't". They want to blame it on
inconsistencies in the clay, but usually it is an inappropriate clay choice.
The clay just isn't suited to their particular way of working. B-mix can be
very unforgiving if you expect it to handle like a traditionally formulated
body."

Now with that in mind please tell us when is B-mix an appropriate choice.
What techniques and ways of working should we use with B-Mix?

Thanks
Gayle Bair- on my last wonderfully soft bag of B-mix and hoping no s-cracks
show up on an order I am about to fire.
Bainbridge Island, WA
--------------------------------------------------------
See Gayle's pottery at http://claybair.com

Jon Pacini on fri 10 aug 01


Hi Gail----Greetings all---- The "appropriate choice" and "technique" I was
referring to is the potters "personal technique" and how that relates to the
clay body. That is, how a potter intuitively works with the clay rather
than to the technique of throwing or slab building in general.
The choice one makes in a clay to use is by definition a very personal one.
You have to respond to the clay and the clay must respond to you. It's the
underlying reason that there are thousands of clay formulas in use. There is
no one "perfect clay body" for every potter, but rather a lot of perfect
bodies for a lot of potters. Trying to find the match can seem like an
impossible task at times.
When I develop a clay body, the characteristics that the clay develops
revolve around how my personality works with the clay. Fortunately there are
enough potters out there whose techniques run parallel to mine that I have
developed a few successful bodies. But I've developed some real duds too.
Just because I can throw 3 foot tall cylinders out of a body doesn't mean
that another potter can. I've learned to send test bodies out to a half a
dozen potters who really torture clay and see what their reaction is to it.
For a body to be successful, it all comes down to how the clay and potter
work together. Some undeniably work better together than others.
And I can't leave this unsaid-----There's a lot of of craft and science
involved in developing a commercially viable clay body. A body must maintain
some rather stringent technical boundaries. The days of a clay maker saying,
"I need a brown sandy body, so I'll mix one scoop of this with two scoops of
that", have long past.
Know your supplier, more than that, know your clay.

Jon Pacini
Clay Manager
Laguna Clay Co


-----Original Message-----
From: Gayle Bair [mailto:gaylebair@bainbridge.net]
Sent: Friday, August 10, 2001 1:09 AM
To: Jon Pacini
Cc: clayart@lsv.ceramics.org
Subject: RE: B-Mix -- cracks and inconsistencies


Jon,
Thank you for your bravery in the line of fire!
I am currently using B-mix after a hiatus of 2 years and do enjoy it's
plasticity.
You mentioned:
"If that looks bad, I recommend replacement and then I try to find out
what went wrong.
If that looks good, I take that bag of clay over to the wheel or slab
roller or extruder and put it through it's paces. I've had enough experience
with clay to know I can't mimic their technique exactly but I try to get a
handle on it from talking to them and then do my best. Usually I try to get
an example of the failure out of them. That helps out tremendously by the
way. If I get the same failures they're getting, I try to figure out why.
If it's technique, I try to find a way around the offending technique
and still end up with the same finished product.
If the technique is inappropriate to the body, I try to talk them into
trying a different body. Hopefully without sounding like a paid spokesman,
for example Dave's Porcelain uses the same minerals in a more traditional
combination.
Many times I find potters who are on the edge of having failures, that
is "sometimes it works, sometimes it doesn't". They want to blame it on
inconsistencies in the clay, but usually it is an inappropriate clay choice.
The clay just isn't suited to their particular way of working. B-mix can be
very unforgiving if you expect it to handle like a traditionally formulated
body."

Now with that in mind please tell us when is B-mix an appropriate choice.
What techniques and ways of working should we use with B-Mix?

Thanks
Gayle Bair- on my last wonderfully soft bag of B-mix and hoping no s-cracks
show up on an order I am about to fire.
Bainbridge Island, WA
--------------------------------------------------------
See Gayle's pottery at http://claybair.com

Timakia@AOL.COM on fri 10 aug 01


Jon of course you are a paid spokesman! LOl. You have to be and someone have
to defend sometimes. I think one can do so much harm and if the other side of
the coin is not there, it can be worse.
We were talking lately alot about technical skills. I am not sure if the
average "clay user" are all skilled in what they do. Some ignore the basic
rules of clay and others simply do not have it.
I believe every potter should at least have a copy of Harry Frasers book
"Ceramic falts and their remedies " on their shelves and read it. All the
things that you explained about using B-mix is written in there.
I just opened up one of my bags of B-mix yesterday. I prefer to wedge my
clay,even if it is de- aired,simply to get an even moist content. I found it
was hard to start wedging it, but once I had the clay "down on the table" it
became workable. My porcelain does the same when it is aged a little.
Did not work any futher yet, but I am curious to see what will come. I worked
with it 2 years ago a little in other circumstances as now.
Regards.
Antoinette.

Antoinette Badenhorst
PO Box 552
Saltillo,MS
38866
http://hometown.aol.com/timakia

Chris Clarke on sat 11 aug 01


Sent this directly to Jon, Sorry,

I've had not one problem with B-Mix. Over the past ten years =
I've changed clay about six times. B-Mix has been my favorite. I am =
not careful with drying, I am rough with my work and sometimes I don't =
even score to attach (I know). Never has a handle dropped off or a =
spout cracked (of course it will now). And out here in SoCal right now =
it's a hundred degrees and you can trim in a matter of an hour, have it =
dry by the next day. I just let it go, sometimes even in the sun. No =
problems. Larger more "important" pieces I do dry on a big slab of =
marble, especially plates.
Yes, it's a little too hard, but I didn't figure that one =
out
until recently. I love this clay, it throws like a dream, for me. My
pieces increased about six inches, up to my shoulder. I'm on my toes : =
)
My 2cents (not from Laguna by the way) chris

And to Gayle, I work wet, I don't allow things to set up much before I =
attach and alter. I think when it gets too dry is when you have =
problems with attachments. And s-cracks happen when I hurry throw and =
don't cone well (this happened with most of my clays so it's my bad)

temecula, california
chris@ccpots.com
www.ccpots.com