John Rodgers on thu 3 aug 06
Lynette Jennings once did a segment of her show on the Louisville
Stoneware operation. I was impressed. I was fortunate enough to catch it
on tape at the time. In the tape, I saw an extruder hose used to supply
clay directly to the jiggering operation. By having the clay delivered
to the jiggering machine right where it would go into the mold, instead
of having a man doing nothing but loading the molds, the clay was
injected directly into the mold as it turned on the machine. It was slick!!
They sure has a nice operation.
John Rodgers
Chelsea, Al
Ben Shelton wrote:
> Louisville stoneware
>
> On a recent trip to Louisville, Kentucky My wife and I went on a tour of the
> Louisville stoneware factory. We were the only 2 people on the tour so we
> got to see the whole operation.
>
> They start with a gray raw clay from a coalfield deposit in
> Clay City, Indiana. It reminds me of foundry hill cream. The clay is a
> fairly pure sedimentary deposit of secondary clay like ball clay. The raw
> clay is blunged in 2 HUGE blungers built into the factory floor. They are
> probably 6ft x 10ft x 12ft deep. Our tour guide said nothing else is added
> to the clay body.
>
> The slip is screened through a really cool 3 tier vibratory screen and
> pumped to a filter press. It is then dried quite a bit. It was about leather
> hard from what I felt. I asked why so dry and they said that filter pressing
> helped to wash out unwanted soluble minerals out of the clay so they wanted
> to get most of the water out of the clay and add back clean water as needed.
>
> The leather hard clay then went into a long mixer trough leading to a
> pugmill. Hot water is added back to the mix and the result is
> somewhere between plastic clay and slip. SLOP is what I call it. This is
> extruded into 10" diameter pieces of pipe about 3ft long for transport to
> the forming workstations.
>
> EVERYTHING I saw formed was either cast or cast/jiggered. It went like this.
>
> First: slip was poured into a series of jigger molds. It was allowed to
> build on the mold surface and fill in the various relief areas on the mold.
> Much of their ware has raised relief and they use the slip coating to ensure
> a complete, blemish free finished surface. Once the slip coat is properly
> set the mold is moved to the jigger where the slop is applied by the
> handful. Te slop is quickly smeared around until judged thick enough by the
> worker then the jigger arm is applied in 2 stages being cleaned between.
>
> A man was making 14" platters (upside down) and told me they usually
> averaged 14% shrinkage. WOW!!! Definitely like ball clay.
>
> >From forming the dry pieces go on to sponging to smooth and round all the
> corners and edges and then apply wax to the bottom. From there they go on to
> decoration which varied from painted on to applied, pre-printed labels. Then
> glaze is sprayed on and the unfired pots are placed in the kiln.
>
>
> The ware is fired in oxidation to 2350f. (about cone 10 right?) The result
> is a SMOOTH bodied clay that is light gray to slightly tan and very
> vitrified by the sound of it. The glaze seems to stay in place well and fit
> the ware extremely well. The base glaze is stark white and not completely
> glossy. It shows evidence of minor pin holing in places but the holes seem
> to have healed over almost completely.
>
> All in all I was greatly surprised at which modern techniques had made it
> into their process and which had not. They had all kinds of modern tools and
> yet they do not employ any kind of chemistry to their clay
> whatsoever. No doubt their glaze has been formulated to accommodate the clay
> but apparently the clay is not formulated to aid the process in any way.
>
> And the slop forming is also strange to me. All the jiggering I have seen
> has been done with plastic clay.
>
> What they do works and yet in my warped brain it seems it could use some
> improvement.
>
> I guess if it aint broke...
>
> Ben
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
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>
>
>
Ben Shelton on thu 3 aug 06
Louisville stoneware
On a recent trip to Louisville, Kentucky My wife and I went on a tour of the
Louisville stoneware factory. We were the only 2 people on the tour so we
got to see the whole operation.
They start with a gray raw clay from a coalfield deposit in
Clay City, Indiana. It reminds me of foundry hill cream. The clay is a
fairly pure sedimentary deposit of secondary clay like ball clay. The raw
clay is blunged in 2 HUGE blungers built into the factory floor. They are
probably 6ft x 10ft x 12ft deep. Our tour guide said nothing else is added
to the clay body.
The slip is screened through a really cool 3 tier vibratory screen and
pumped to a filter press. It is then dried quite a bit. It was about leather
hard from what I felt. I asked why so dry and they said that filter pressing
helped to wash out unwanted soluble minerals out of the clay so they wanted
to get most of the water out of the clay and add back clean water as needed.
The leather hard clay then went into a long mixer trough leading to a
pugmill. Hot water is added back to the mix and the result is
somewhere between plastic clay and slip. SLOP is what I call it. This is
extruded into 10" diameter pieces of pipe about 3ft long for transport to
the forming workstations.
EVERYTHING I saw formed was either cast or cast/jiggered. It went like this.
First: slip was poured into a series of jigger molds. It was allowed to
build on the mold surface and fill in the various relief areas on the mold.
Much of their ware has raised relief and they use the slip coating to ensure
a complete, blemish free finished surface. Once the slip coat is properly
set the mold is moved to the jigger where the slop is applied by the
handful. Te slop is quickly smeared around until judged thick enough by the
worker then the jigger arm is applied in 2 stages being cleaned between.
A man was making 14" platters (upside down) and told me they usually
averaged 14% shrinkage. WOW!!! Definitely like ball clay.
From forming the dry pieces go on to sponging to smooth and round all the
corners and edges and then apply wax to the bottom. From there they go on to
decoration which varied from painted on to applied, pre-printed labels. Then
glaze is sprayed on and the unfired pots are placed in the kiln.
The ware is fired in oxidation to 2350f. (about cone 10 right?) The result
is a SMOOTH bodied clay that is light gray to slightly tan and very
vitrified by the sound of it. The glaze seems to stay in place well and fit
the ware extremely well. The base glaze is stark white and not completely
glossy. It shows evidence of minor pin holing in places but the holes seem
to have healed over almost completely.
All in all I was greatly surprised at which modern techniques had made it
into their process and which had not. They had all kinds of modern tools and
yet they do not employ any kind of chemistry to their clay
whatsoever. No doubt their glaze has been formulated to accommodate the clay
but apparently the clay is not formulated to aid the process in any way.
And the slop forming is also strange to me. All the jiggering I have seen
has been done with plastic clay.
What they do works and yet in my warped brain it seems it could use some
improvement.
I guess if it aint broke...
Ben
steve blankenbeker on thu 3 aug 06
Dear Ben,
I have been in the shop when I was with Cedar Heights
Clay, maybe 10 or 12 years ago. Working for a
business that ground fireclays, I can appreciate both
sides. Robinson-Ransbottom Pottery in Roseville, Ohio
was the same way. They were still processing
fireclays with a blunger and filter press in the same
fashion as they did in 1900 when the plant closed down
a few years ago.
There is something to be said about the old fashioned
way, especially with regards to dust control.
Ransbottom would "steal" about 75% of the best part of
the clay with the blunging, and throw out the coarse
stuff that didn't pass through the screenings. The
cost of the crude clay was so cheap that losing 25%
didn't matter. Then all processes - slip casting,
jiggering and pressing - all started with the same
blunged clay. When you get a ground clay - like
Goldart - you get 100% of what was thrown in the mill
- good and bad. The alternative of buying ground
fireclays to make their wares means paying more
upfront, wet mixers for the batches where discharging
of bags would require additional dust controls, bag or
supersack disposal - the list goes on. I knew one
manager in a similar type operation who told me "It's
not bone china, and the customers don't want bone
china. Let them go to Pfaltzgraff if they want a more
refined piece. Our processes add a unique character to
our ware" I personally think, whenever possible,
blunging is a wonderful way to process clays. It also
will allow the clay particles to liberate freely from
one another, instead of beeing forcibly liberated with
machinery.
Thanks,
Steve
--- Ben Shelton wrote:
> Louisville stoneware
>
> On a recent trip to Louisville, Kentucky My wife and
> I went on a tour of the
> Louisville stoneware factory. We were the only 2
> people on the tour so we
> got to see the whole operation.
>
> They start with a gray raw clay from a coalfield
> deposit in
> Clay City, Indiana. It reminds me of foundry hill
> cream. The clay is a
> fairly pure sedimentary deposit of secondary clay
> like ball clay. The raw
> clay is blunged in 2 HUGE blungers built into the
> factory floor. They are
> probably 6ft x 10ft x 12ft deep. Our tour guide said
> nothing else is added
> to the clay body.
>
> The slip is screened through a really cool 3 tier
> vibratory screen and
> pumped to a filter press. It is then dried quite a
> bit. It was about leather
> hard from what I felt. I asked why so dry and they
> said that filter pressing
> helped to wash out unwanted soluble minerals out of
> the clay so they wanted
> to get most of the water out of the clay and add
> back clean water as needed.
>
> The leather hard clay then went into a long mixer
> trough leading to a
> pugmill. Hot water is added back to the mix and the
> result is
> somewhere between plastic clay and slip. SLOP is
> what I call it. This is
> extruded into 10" diameter pieces of pipe about 3ft
> long for transport to
> the forming workstations.
>
> EVERYTHING I saw formed was either cast or
> cast/jiggered. It went like this.
>
> First: slip was poured into a series of jigger
> molds. It was allowed to
> build on the mold surface and fill in the various
> relief areas on the mold.
> Much of their ware has raised relief and they use
> the slip coating to ensure
> a complete, blemish free finished surface. Once the
> slip coat is properly
> set the mold is moved to the jigger where the slop
> is applied by the
> handful. Te slop is quickly smeared around until
> judged thick enough by the
> worker then the jigger arm is applied in 2 stages
> being cleaned between.
>
> A man was making 14" platters (upside down) and told
> me they usually
> averaged 14% shrinkage. WOW!!! Definitely like ball
> clay.
>
> From forming the dry pieces go on to sponging to
> smooth and round all the
> corners and edges and then apply wax to the bottom.
> From there they go on to
> decoration which varied from painted on to applied,
> pre-printed labels. Then
> glaze is sprayed on and the unfired pots are placed
> in the kiln.
>
>
> The ware is fired in oxidation to 2350f. (about cone
> 10 right?) The result
> is a SMOOTH bodied clay that is light gray to
> slightly tan and very
> vitrified by the sound of it. The glaze seems to
> stay in place well and fit
> the ware extremely well. The base glaze is stark
> white and not completely
> glossy. It shows evidence of minor pin holing in
> places but the holes seem
> to have healed over almost completely.
>
> All in all I was greatly surprised at which modern
> techniques had made it
> into their process and which had not. They had all
> kinds of modern tools and
> yet they do not employ any kind of chemistry to
> their clay
> whatsoever. No doubt their glaze has been formulated
> to accommodate the clay
> but apparently the clay is not formulated to aid the
> process in any way.
>
> And the slop forming is also strange to me. All the
> jiggering I have seen
> has been done with plastic clay.
>
> What they do works and yet in my warped brain it
> seems it could use some
> improvement.
>
> I guess if it aint broke...
>
> Ben
>
>
______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change
> your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be
> reached at melpots@pclink.com.
>
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