Susan Hirsch on fri 5 feb 10
Hi everyone! This is my first time posting anything. I have gotten some=
=3D
great information on here reading the archives, and I'm desperate right n=
=3D
ow
so I'm hoping somebody who knows more about this than I do can help me. =
=3D
I
will set up a shrine in my house to anyone who can advise me how to fix t=
=3D
his
lumpy, gelatinous batch of slip!
The recipe itself is perfectly respectable, and is not at fault, but I'm
posting it here in case it provides you any insight into what can be done=
=3D
to
fix my batch. It's Wally's Wonderslip from Cushing's Handbook, as follow=
=3D
s:
Custer Feldspar 26
Whiting 1
Goldart 21
Tenn. Ball Clay 10
EPK 12=3D20
Flint 30
plus:
Water 35%
Sodium Silicate 198.5ml/100lbs
Darvan #7 198.5ml/100lbs
I can't afford a proper slip mixer, so I'm using a 33 gallon garbage bin =
=3D
on
wheels. My first mistake was adding the dry ingredients first (I was
mindlessly following directions for mixing clay in a huge mixer we had at=
=3D
KCAI). So that caused a lot of trouble getting all the dry clay (especia=
=3D
lly
the ball clay, I'm guessing) off the bottom.=3D20=3D20
I tried using a paint mixer on my drill (HA!) which broke in about 5
minutes. Then I rented a bigger better drill and tried to use a mortar
mixing attachment. Well, that worked alright until the motor started
smoking, so I stopped that quickly. Then I rented a 3/4" drill (two, or
three handed dealy...about the biggest you can get) with one speed which =
=3D
was
so strong it whipped all kinds of air into the batch...but it broke up th=
=3D
e
chunks so I kept it up hoping the air would eventually work its way out (=
=3D
if
anyone could comment on that I would appreciate it. I'm not sure if I'm
being completely foolish thinking that this air might eventually be able =
=3D
to
be removed somehow.)=3D20=3D20
It was all smooth, for a while, except for the air bubbles. So I left it=
=3D
to
sit for a few days, stirring it occasionally. It seemed to be getting
thicker, so I added more water, so that the total was about 50 lbs instea=
=3D
d
of 35. And I only added the amount of deflocculent for 100 lbs of clay
(because I'm assuming it means for the 100 lbs dry clay?)=3D20
There is a large gap between the surface of the slip and the lid of the b=
=3D
in,
and that might be the major cause of the coagulation on the top. But it
seems like more than just drying out...it seems to be gelling up on the t=
=3D
op
4 inches or so, which means I should add more deflocculent, right? And i=
=3D
t's
settling out on the bottom too. I just wanted some more experienced
opinions on this before I over-do the deflocculent. I've already gone wa=
=3D
y
beyond my budget; I'd hate to have to pitch $200 worth of slip and work n=
=3D
ow.=3D20=3D20
I would really appreciate any tips to save this batch you can give me!=3D20=
=3D
Thank you!!!
~Susan
John Rodgers on sat 6 feb 10
Susan,
If I understand you correctly, you have slip you can stir - and it is
adequately mixed, but you are having problems with the mixture going to
a jell state on top???
If that is the case, it sounds as if you need to take some steps to get
the process under control.
I would suggest the following - assuming the slip thoroughly mixed.
1) Mix thoroughly for a bit
2) Determine the density of the slip. Do this by weighing equal volumes
of water and slip. Divide the weight of the water into the weight of the
slip. The value derived will be the density. The density of the slip
should be 1.75 to 1.85. If the density number is low - you need to add
some clay to bring the density back within in the range shown.. If the
density is hight, you need to add some water to reduce the density back
into range.
DO NOT add any other chemicals until density has been determined and is
corrected to between 1.75 and 1.85.
3) Once the density is between 1.75 and 1.85, you are ready to adjust
the viscosity of the slip with a deflocculant. Some use a commercial
deflocculant - Darvan. Others swear by Sodium Silicate. I prefer the
latter myself. The Sodium silicate must be mixed 50/50 with water just
before use.
4) Viscosity Test - assuming you have not already added to much
deflocculant, you will test the slip viscosity. To do this properly, you
need a viscosity cup. This is a simple plastic cup used primarily to
adjust the flow of paint, but it works extraordinarily well for testing
slip and glazes. Some companies - and in some books - there is a call
for the use of rubber stoppers, plastic tubing or glass tubing, and an
Erlenmeyer flask - all of which is expensive, something like $25 to $50
or so, depending on the company. You do not need this to test viscosity.
Acquire a Viscosity cup part number TL497 Viscosity Cup from New Mexico
Clay for $5.95. The cup has a calibrated hole in the very bottom. Dip
the cup into the slip so it is full and level, note the time, then when
the cup drains out and the dripping stops - note the time. The goal is
for the cup to drain in 23 seconds. If you can get it to work at 30
seconds it will work and the slip will be OK, but 23 seconds is ideal.
If the slip is thick and the time is long - that is - viscosity cup
drain time is greater than 30 seconds, drizzle just a tiny bit of the
Silicate and water into the slip as you are mixing. It should be obvious
if the slip moves to loosen up. The slip will become much more fluid.
Drizzle, test, drizzle, test - continue until you get it down pat. and
the slip flows out of the cup at 23 seconds - 30 sec is ok.
If the slip seems to get thicker- in all likelihood you have over
flocculated, and Need to add more clay.
Hope this helps.
John Rodgers
Chelses
John Rodgers
Clayartist and Moldmaker
88'GL VW Bus Driver
Chelsea, AL
Http://www.moldhaus.com
Susan Hirsch wrote:
> Hi everyone! This is my first time posting anything. I have gotten some
> great information on here reading the archives, and I'm desperate right n=
ow
> so I'm hoping somebody who knows more about this than I do can help me. =
I
> will set up a shrine in my house to anyone who can advise me how to fix t=
his
> lumpy, gelatinous batch of slip!
>
> The recipe itself is perfectly respectable, and is not at fault, but I'm
> posting it here in case it provides you any insight into what can be done=
to
> fix my batch. It's Wally's Wonderslip from Cushing's Handbook, as follow=
s:
>
> Custer Feldspar 26
> Whiting 1
> Goldart 21
> Tenn. Ball Clay 10
> EPK 12
> Flint 30
>
> plus:
>
> Water 35%
> Sodium Silicate 198.5ml/100lbs
> Darvan #7 198.5ml/100lbs
>
>
> I can't afford a proper slip mixer, so I'm using a 33 gallon garbage bin =
on
> wheels. My first mistake was adding the dry ingredients first (I was
> mindlessly following directions for mixing clay in a huge mixer we had at
> KCAI). So that caused a lot of trouble getting all the dry clay (especia=
lly
> the ball clay, I'm guessing) off the bottom.
>
> I tried using a paint mixer on my drill (HA!) which broke in about 5
> minutes. Then I rented a bigger better drill and tried to use a mortar
> mixing attachment. Well, that worked alright until the motor started
> smoking, so I stopped that quickly. Then I rented a 3/4" drill (two, or
> three handed dealy...about the biggest you can get) with one speed which =
was
> so strong it whipped all kinds of air into the batch...but it broke up th=
e
> chunks so I kept it up hoping the air would eventually work its way out (=
if
> anyone could comment on that I would appreciate it. I'm not sure if I'm
> being completely foolish thinking that this air might eventually be able =
to
> be removed somehow.)
>
> It was all smooth, for a while, except for the air bubbles. So I left it=
to
> sit for a few days, stirring it occasionally. It seemed to be getting
> thicker, so I added more water, so that the total was about 50 lbs instea=
d
> of 35. And I only added the amount of deflocculent for 100 lbs of clay
> (because I'm assuming it means for the 100 lbs dry clay?)
>
> There is a large gap between the surface of the slip and the lid of the b=
in,
> and that might be the major cause of the coagulation on the top. But it
> seems like more than just drying out...it seems to be gelling up on the t=
op
> 4 inches or so, which means I should add more deflocculent, right? And i=
t's
> settling out on the bottom too. I just wanted some more experienced
> opinions on this before I over-do the deflocculent. I've already gone wa=
y
> beyond my budget; I'd hate to have to pitch $200 worth of slip and work n=
ow.
>
> I would really appreciate any tips to save this batch you can give me!
> Thank you!!!
>
> ~Susan
>
>
>
Marcia Selsor on sat 6 feb 10
I made slip decades ago in a 33 gallon bucket. I followed John Kenny's =3D
directions where=3D20
after mixing the batch, you stir for 10 mintues every day for a week or =3D
so.
It worked perfectly. Try to find the book and see what you may have =3D
missed OR start stirring=3D20
for the next week. I got a big drill with the handle on the end and a =3D
paint mixer.=3D20
I successfully cast large molds 2ft -30" . I built a table with a hinge =3D
section so I could pour the excess=3D20
out of the mold with the mold proper strapped to the hinged part of the =3D
table.
Maybe you just need to do the repetitive stirring for a week.
Marcis Selsor
On Feb 5, 2010, at 7:07 PM, Susan Hirsch wrote:
> Hi everyone! This is my first time posting anything. I have gotten =3D
some
> great information on here reading the archives, and I'm desperate =3D
right now
> so I'm hoping somebody who knows more about this than I do can help =3D
me. I
> will set up a shrine in my house to anyone who can advise me how to =3D
fix this
> lumpy, gelatinous batch of slip!
>=3D20
> The recipe itself is perfectly respectable, and is not at fault, but =3D
I'm
> posting it here in case it provides you any insight into what can be =3D
done to
> fix my batch. It's Wally's Wonderslip from Cushing's Handbook, as =3D
follows:
>=3D20
> Custer Feldspar 26
> Whiting 1
> Goldart 21
> Tenn. Ball Clay 10
> EPK 12=3D20
> Flint 30
>=3D20
> plus:
>=3D20
> Water 35%
> Sodium Silicate 198.5ml/100lbs
> Darvan #7 198.5ml/100lbs
>=3D20
>=3D20
> I can't afford a proper slip mixer, so I'm using a 33 gallon garbage =3D
bin on
> wheels. My first mistake was adding the dry ingredients first (I was
> mindlessly following directions for mixing clay in a huge mixer we had =
=3D
at
> KCAI). So that caused a lot of trouble getting all the dry clay =3D
(especially
> the ball clay, I'm guessing) off the bottom. =3D20
>=3D20
> I tried using a paint mixer on my drill (HA!) which broke in about 5
> minutes. Then I rented a bigger better drill and tried to use a =3D
mortar
> mixing attachment. Well, that worked alright until the motor started
> smoking, so I stopped that quickly. Then I rented a 3/4" drill (two, =3D
or
> three handed dealy...about the biggest you can get) with one speed =3D
which was
> so strong it whipped all kinds of air into the batch...but it broke up =
=3D
the
> chunks so I kept it up hoping the air would eventually work its way =3D
out (if
> anyone could comment on that I would appreciate it. I'm not sure if =3D
I'm
> being completely foolish thinking that this air might eventually be =3D
able to
> be removed somehow.) =3D20
>=3D20
> It was all smooth, for a while, except for the air bubbles. So I left =
=3D
it to
> sit for a few days, stirring it occasionally. It seemed to be getting
> thicker, so I added more water, so that the total was about 50 lbs =3D
instead
> of 35. And I only added the amount of deflocculent for 100 lbs of =3D
clay
> (because I'm assuming it means for the 100 lbs dry clay?)=3D20
>=3D20
> There is a large gap between the surface of the slip and the lid of =3D
the bin,
> and that might be the major cause of the coagulation on the top. But =3D
it
> seems like more than just drying out...it seems to be gelling up on =3D
the top
> 4 inches or so, which means I should add more deflocculent, right? =3D
And it's
> settling out on the bottom too. I just wanted some more experienced
> opinions on this before I over-do the deflocculent. I've already gone =
=3D
way
> beyond my budget; I'd hate to have to pitch $200 worth of slip and =3D
work now. =3D20
>=3D20
> I would really appreciate any tips to save this batch you can give me!=3D=
20=3D
> Thank you!!!
>=3D20
> ~Susan
>=3D20
Marcia Selsor
http://www.marciaselsor.com
susan hirsch on sat 6 feb 10
Marcia: I like your hinged table idea! I won't have time to build one (I
chase a 3 yr old and a 1 yr old around most of the day, and barely have tim=
e
to get this slip fixed and my molds made) but it sounds like a great future
project.
May: It's a good idea to try troubleshooting in a smaller bucket first and
testing it. I'll check the density (is that what you meant?) and that
should give me a better vantage point as well. Thank you. Sometimes I
think we just need someone with a different perspective to remind us what w=
e
should be doing :)
On Sat, Feb 6, 2010 at 12:14 PM, May Luk wrote:
> Hi Susan;
>
> Did you weigh out 250 gm and see what is the weight?
>
> If I read this correctly, you have 100 lbs of dry material and 50 lbs
> of water. It appears that you need to add more clay before adding
> deflocculant.
>
> If everything is mixed thoroughly, maybe you can eyeball a portion of
> it (like 25%) into a separate bucket. Based on the weight of the slip
> and determined whether to add deflocc or dry materials. But only do it
> in small batches, cast and fired successfully, before you transfer the
> procedure to a large batch.
>
> My last batch of slip, I have ordered the wrong slip (not for slip
> cast) In addition, I did my first reclaim, but in the wrong order.
> Everything gelled up and I fixed and fixed and it went downhill every
> time. In the end, I just chucked the whole thing. It wasn't worth the
> time and the messiness.
>
> I have seen my right out of college studio mate did something similar
> to a 100 lbs of clay without small batch testing. In school, they were
> doing something tried and tested by the instructor, so she didn't know
> how to trouble shoot. Next time, you might want to start with only 10
> - 25 lbs dry materials. Just a thought.
>
> Best Regards
> May
>
> On Fri, Feb 5, 2010 at 8:07 PM, Susan Hirsch wrote=
:
> > Hi everyone! This is my first time posting anything. I have gotten so=
me
> > great information on here reading the archives, and I'm desperate right
> now
> > so I'm hoping somebody who knows more about this than I do can help me.
> I
> > will set up a shrine in my house to anyone who can advise me how to fix
> this
> > lumpy, gelatinous batch of slip!
> >
> > The recipe itself is perfectly respectable, and is not at fault, but I'=
m
> > posting it here in case it provides you any insight into what can be do=
ne
> to
> > fix my batch. It's Wally's Wonderslip from Cushing's Handbook, as
> follows:
> >
> > Custer Feldspar 26
> > Whiting 1
> > Goldart 21
> > Tenn. Ball Clay 10
> > EPK 12
> > Flint 30
> >
> > plus:
> >
> > Water 35%
> > Sodium Silicate 198.5ml/100lbs
> > Darvan #7 198.5ml/100lbs
> >
> >
> > I can't afford a proper slip mixer, so I'm using a 33 gallon garbage bi=
n
> on
> > wheels. My first mistake was adding the dry ingredients first (I was
> > mindlessly following directions for mixing clay in a huge mixer we had =
at
> > KCAI). So that caused a lot of trouble getting all the dry clay
> (especially
> > the ball clay, I'm guessing) off the bottom.
> >
> > I tried using a paint mixer on my drill (HA!) which broke in about 5
> > minutes. Then I rented a bigger better drill and tried to use a mortar
> > mixing attachment. Well, that worked alright until the motor started
> > smoking, so I stopped that quickly. Then I rented a 3/4" drill (two, o=
r
> > three handed dealy...about the biggest you can get) with one speed whic=
h
> was
> > so strong it whipped all kinds of air into the batch...but it broke up
> the
> > chunks so I kept it up hoping the air would eventually work its way out
> (if
> > anyone could comment on that I would appreciate it. I'm not sure if I'=
m
> > being completely foolish thinking that this air might eventually be abl=
e
> to
> > be removed somehow.)
> >
> > It was all smooth, for a while, except for the air bubbles. So I left =
it
> to
> > sit for a few days, stirring it occasionally. It seemed to be getting
> > thicker, so I added more water, so that the total was about 50 lbs
> instead
> > of 35. And I only added the amount of deflocculent for 100 lbs of clay
> > (because I'm assuming it means for the 100 lbs dry clay?)
> >
> > There is a large gap between the surface of the slip and the lid of the
> bin,
> > and that might be the major cause of the coagulation on the top. But i=
t
> > seems like more than just drying out...it seems to be gelling up on the
> top
> > 4 inches or so, which means I should add more deflocculent, right? And
> it's
> > settling out on the bottom too. I just wanted some more experienced
> > opinions on this before I over-do the deflocculent. I've already gone
> way
> > beyond my budget; I'd hate to have to pitch $200 worth of slip and work
> now.
> >
> > I would really appreciate any tips to save this batch you can give me!
> > Thank you!!!
> >
> > ~Susan
> >
>
>
>
> --
> http://twitter.com/MayLuk
>
May Luk on sat 6 feb 10
Hi Susan;
Did you weigh out 250 gm and see what is the weight?
If I read this correctly, you have 100 lbs of dry material and 50 lbs
of water. It appears that you need to add more clay before adding
deflocculant.
If everything is mixed thoroughly, maybe you can eyeball a portion of
it (like 25%) into a separate bucket. Based on the weight of the slip
and determined whether to add deflocc or dry materials. But only do it
in small batches, cast and fired successfully, before you transfer the
procedure to a large batch.
My last batch of slip, I have ordered the wrong slip (not for slip
cast) In addition, I did my first reclaim, but in the wrong order.
Everything gelled up and I fixed and fixed and it went downhill every
time. In the end, I just chucked the whole thing. It wasn't worth the
time and the messiness.
I have seen my right out of college studio mate did something similar
to a 100 lbs of clay without small batch testing. In school, they were
doing something tried and tested by the instructor, so she didn't know
how to trouble shoot. Next time, you might want to start with only 10
- 25 lbs dry materials. Just a thought.
Best Regards
May
On Fri, Feb 5, 2010 at 8:07 PM, Susan Hirsch wrote:
> Hi everyone! =3DA0This is my first time posting anything. =3DA0I have got=
ten =3D
some
> great information on here reading the archives, and I'm desperate right n=
=3D
ow
> so I'm hoping somebody who knows more about this than I do can help me. =
=3D
=3DA0I
> will set up a shrine in my house to anyone who can advise me how to fix t=
=3D
his
> lumpy, gelatinous batch of slip!
>
> The recipe itself is perfectly respectable, and is not at fault, but I'm
> posting it here in case it provides you any insight into what can be done=
=3D
to
> fix my batch. =3DA0It's Wally's Wonderslip from Cushing's Handbook, as fo=
ll=3D
ows:
>
> Custer Feldspar 26
> Whiting =3DA0 =3DA0 1
> Goldart =3DA021
> Tenn. Ball Clay =3DA010
> EPK =3DA012
> Flint =3DA030
>
> plus:
>
> Water 35%
> Sodium Silicate 198.5ml/100lbs
> Darvan #7 =3DA0198.5ml/100lbs
>
>
> I can't afford a proper slip mixer, so I'm using a 33 gallon garbage bin =
=3D
on
> wheels. =3DA0My first mistake was adding the dry ingredients first (I was
> mindlessly following directions for mixing clay in a huge mixer we had at
> KCAI). =3DA0So that caused a lot of trouble getting all the dry clay (esp=
ec=3D
ially
> the ball clay, I'm guessing) off the bottom.
>
> I tried using a paint mixer on my drill (HA!) which broke in about 5
> minutes. =3DA0Then I rented a bigger better drill and tried to use a mort=
ar
> mixing attachment. =3DA0Well, that worked alright until the motor started
> smoking, so I stopped that quickly. =3DA0Then I rented a 3/4" drill (two,=
o=3D
r
> three handed dealy...about the biggest you can get) with one speed which =
=3D
was
> so strong it whipped all kinds of air into the batch...but it broke up th=
=3D
e
> chunks so I kept it up hoping the air would eventually work its way out (=
=3D
if
> anyone could comment on that I would appreciate it. =3DA0I'm not sure if =
I'=3D
m
> being completely foolish thinking that this air might eventually be able =
=3D
to
> be removed somehow.)
>
> It was all smooth, for a while, except for the air bubbles. =3DA0So I lef=
t =3D
it to
> sit for a few days, stirring it occasionally. =3DA0It seemed to be gettin=
g
> thicker, so I added more water, so that the total was about 50 lbs instea=
=3D
d
> of 35. =3DA0And I only added the amount of deflocculent for 100 lbs of cl=
ay
> (because I'm assuming it means for the 100 lbs dry clay?)
>
> There is a large gap between the surface of the slip and the lid of the b=
=3D
in,
> and that might be the major cause of the coagulation on the top. =3DA0But=
i=3D
t
> seems like more than just drying out...it seems to be gelling up on the t=
=3D
op
> 4 inches or so, which means I should add more deflocculent, right? =3DA0A=
nd=3D
it's
> settling out on the bottom too. =3DA0I just wanted some more experienced
> opinions on this before I over-do the deflocculent. =3DA0I've already gon=
e =3D
way
> beyond my budget; I'd hate to have to pitch $200 worth of slip and work n=
=3D
ow.
>
> I would really appreciate any tips to save this batch you can give me!
> Thank you!!!
>
> ~Susan
>
--=3D20
http://twitter.com/MayLuk
ivor & olive lewis on sun 7 feb 10
Dear Susan Hirsch,
Quite a quandary. Almost a comedy of errors.
To resuscitate your batch of clay allow it to dry, but do not heat above 10=
5
deg C, say 220 F. Crush to pea size and smaller. Put 35 Lbs of water in a
tub. Mix in your deflocculants. Add the Clay to the Water. Do not disturb
it. Leave it to stand undisturbed for twenty four hours or longer. This
period is called "The Slaking Time".
Had you not been impatient after adding the dry ingredients to your water,
even if they had been added without prior mixing and allowed to slake, they
would have mixed easily to a pourable fluid.
I have been studying the property of plasticity, trying to learn if and how
Flocs form. Here, I am making a bold assumption that Clay/Water mixtures
that have not been doped with Deflocculants must be flocculated. If 70 gram=
s
of ball clay are sifted onto 30 grams of pure water and allowed to stand
undisturbed, within twenty minutes all the water will have been drawn into
the clay by capillary action.
My suggestion for future batches of casting slip would be to mix all the dr=
y
ingredients thoroughly and all the fluid ingredients thoroughly then add th=
e
dry mixture to the liquid mixture. Allow the contents of your tub to stand,
to Slake, for 24 hours or longer before mixing (blunging).
Best regards,
Ivor Lewis,
Redhill,
South Australia
John Rodgers on sun 7 feb 10
I forgot to mention ---
Of the last step, if you have added to much Silicate/water mix (or
Darvan for that matter) - the slip will get thicker, and the only way to
correct that problem is by going back through the process and adjusting
the density. Then you can address the viscosity. But it is crucial that
you get the density properly adjusted. Without that, you cannot go
forward with success. Once density is correct - adjusting viscosity with
the silicate/water mix is easy.
John Rodgers
Clayartist and Moldmaker
88'GL VW Bus Driver
Chelsea, AL
Http://www.moldhaus.com
John Rodgers wrote:
> Susan,
>
> If I understand you correctly, you have slip you can stir - and it is
> adequately mixed, but you are having problems with the mixture going to
> a jell state on top???
>
> If that is the case, it sounds as if you need to take some steps to get
> the process under control.
>
> I would suggest the following - assuming the slip thoroughly mixed.
>
> 1) Mix thoroughly for a bit
> 2) Determine the density of the slip. Do this by weighing equal volumes
> of water and slip. Divide the weight of the water into the weight of the
> slip. The value derived will be the density. The density of the slip
> should be 1.75 to 1.85. If the density number is low - you need to add
> some clay to bring the density back within in the range shown.. If the
> density is hight, you need to add some water to reduce the density back
> into range.
>
> DO NOT add any other chemicals until density has been determined and is
> corrected to between 1.75 and 1.85.
>
> 3) Once the density is between 1.75 and 1.85, you are ready to adjust
> the viscosity of the slip with a deflocculant. Some use a commercial
> deflocculant - Darvan. Others swear by Sodium Silicate. I prefer the
> latter myself. The Sodium silicate must be mixed 50/50 with water just
> before use.
>
> 4) Viscosity Test - assuming you have not already added to much
> deflocculant, you will test the slip viscosity. To do this properly, you
> need a viscosity cup. This is a simple plastic cup used primarily to
> adjust the flow of paint, but it works extraordinarily well for testing
> slip and glazes. Some companies - and in some books - there is a call
> for the use of rubber stoppers, plastic tubing or glass tubing, and an
> Erlenmeyer flask - all of which is expensive, something like $25 to $50
> or so, depending on the company. You do not need this to test viscosity.
>
> Acquire a Viscosity cup part number TL497 Viscosity Cup from New Mexico
> Clay for $5.95. The cup has a calibrated hole in the very bottom. Dip
> the cup into the slip so it is full and level, note the time, then when
> the cup drains out and the dripping stops - note the time. The goal is
> for the cup to drain in 23 seconds. If you can get it to work at 30
> seconds it will work and the slip will be OK, but 23 seconds is ideal.
>
> If the slip is thick and the time is long - that is - viscosity cup
> drain time is greater than 30 seconds, drizzle just a tiny bit of the
> Silicate and water into the slip as you are mixing. It should be obvious
> if the slip moves to loosen up. The slip will become much more fluid.
> Drizzle, test, drizzle, test - continue until you get it down pat. and
> the slip flows out of the cup at 23 seconds - 30 sec is ok.
>
> If the slip seems to get thicker- in all likelihood you have over
> flocculated, and Need to add more clay.
>
>
> Hope this helps.
>
> John Rodgers
>
> Chelses
>
>
> John Rodgers
> Clayartist and Moldmaker
> 88'GL VW Bus Driver
> Chelsea, AL
> Http://www.moldhaus.com
>
>
>
> Susan Hirsch wrote:
>> Hi everyone! This is my first time posting anything. I have gotten
>> some
>> great information on here reading the archives, and I'm desperate
>> right now
>> so I'm hoping somebody who knows more about this than I do can help
>> me. I
>> will set up a shrine in my house to anyone who can advise me how to
>> fix this
>> lumpy, gelatinous batch of slip!
>>
>> The recipe itself is perfectly respectable, and is not at fault, but I'm
>> posting it here in case it provides you any insight into what can be
>> done to
>> fix my batch. It's Wally's Wonderslip from Cushing's Handbook, as
>> follows:
>>
>> Custer Feldspar 26
>> Whiting 1
>> Goldart 21
>> Tenn. Ball Clay 10
>> EPK 12
>> Flint 30
>>
>> plus:
>>
>> Water 35%
>> Sodium Silicate 198.5ml/100lbs
>> Darvan #7 198.5ml/100lbs
>>
>>
>> I can't afford a proper slip mixer, so I'm using a 33 gallon garbage
>> bin on
>> wheels. My first mistake was adding the dry ingredients first (I was
>> mindlessly following directions for mixing clay in a huge mixer we
>> had at
>> KCAI). So that caused a lot of trouble getting all the dry clay
>> (especially
>> the ball clay, I'm guessing) off the bottom.
>>
>> I tried using a paint mixer on my drill (HA!) which broke in about 5
>> minutes. Then I rented a bigger better drill and tried to use a mortar
>> mixing attachment. Well, that worked alright until the motor started
>> smoking, so I stopped that quickly. Then I rented a 3/4" drill (two, or
>> three handed dealy...about the biggest you can get) with one speed
>> which was
>> so strong it whipped all kinds of air into the batch...but it broke
>> up the
>> chunks so I kept it up hoping the air would eventually work its way
>> out (if
>> anyone could comment on that I would appreciate it. I'm not sure if I'm
>> being completely foolish thinking that this air might eventually be
>> able to
>> be removed somehow.)
>>
>> It was all smooth, for a while, except for the air bubbles. So I
>> left it to
>> sit for a few days, stirring it occasionally. It seemed to be getting
>> thicker, so I added more water, so that the total was about 50 lbs
>> instead
>> of 35. And I only added the amount of deflocculent for 100 lbs of clay
>> (because I'm assuming it means for the 100 lbs dry clay?)
>>
>> There is a large gap between the surface of the slip and the lid of
>> the bin,
>> and that might be the major cause of the coagulation on the top. But it
>> seems like more than just drying out...it seems to be gelling up on
>> the top
>> 4 inches or so, which means I should add more deflocculent, right?
>> And it's
>> settling out on the bottom too. I just wanted some more experienced
>> opinions on this before I over-do the deflocculent. I've already
>> gone way
>> beyond my budget; I'd hate to have to pitch $200 worth of slip and
>> work now.
>>
>> I would really appreciate any tips to save this batch you can give me!
>> Thank you!!!
>>
>> ~Susan
>>
>>
>>
>
>
susan hirsch on sun 7 feb 10
Thank you so much for your clear and thorough response John. That is
exactly what I'm going to do.
Cheers!
Susan
On Sat, Feb 6, 2010 at 9:57 PM, John Rodgers wrote:
> Susan,
>
> If I understand you correctly, you have slip you can stir - and it is
> adequately mixed, but you are having problems with the mixture going to a
> jell state on top???
>
> If that is the case, it sounds as if you need to take some steps to get t=
he
> process under control.
>
> I would suggest the following - assuming the slip thoroughly mixed.
>
> 1) Mix thoroughly for a bit
> 2) Determine the density of the slip. Do this by weighing equal volumes =
of
> water and slip. Divide the weight of the water into the weight of the sli=
p.
> The value derived will be the density. The density of the slip should be
> 1.75 to 1.85. If the density number is low - you need to add some clay t=
o
> bring the density back within in the range shown.. If the density is high=
t,
> you need to add some water to reduce the density back into range.
>
> DO NOT add any other chemicals until density has been determined and is
> corrected to between 1.75 and 1.85.
>
> 3) Once the density is between 1.75 and 1.85, you are ready to adjust the
> viscosity of the slip with a deflocculant. Some use a commercial
> deflocculant - Darvan. Others swear by Sodium Silicate. I prefer the latt=
er
> myself. The Sodium silicate must be mixed 50/50 with water just before u=
se.
>
> 4) Viscosity Test - assuming you have not already added to much
> deflocculant, you will test the slip viscosity. To do this properly, you
> need a viscosity cup. This is a simple plastic cup used primarily to adju=
st
> the flow of paint, but it works extraordinarily well for testing slip and
> glazes. Some companies - and in some books - there is a call for the use =
of
> rubber stoppers, plastic tubing or glass tubing, and an Erlenmeyer flask =
-
> all of which is expensive, something like $25 to $50 or so, depending on =
the
> company. You do not need this to test viscosity.
>
> Acquire a Viscosity cup part number TL497 Viscosity Cup from New Mexico
> Clay for $5.95. The cup has a calibrated hole in the very bottom. Dip the
> cup into the slip so it is full and level, note the time, then when the c=
up
> drains out and the dripping stops - note the time. The goal is for the cu=
p
> to drain in 23 seconds. If you can get it to work at 30 seconds it will w=
ork
> and the slip will be OK, but 23 seconds is ideal.
>
> If the slip is thick and the time is long - that is - viscosity cup drain
> time is greater than 30 seconds, drizzle just a tiny bit of the Silicate =
and
> water into the slip as you are mixing. It should be obvious if the slip
> moves to loosen up. The slip will become much more fluid. Drizzle, test,
> drizzle, test - continue until you get it down pat. and the slip flows ou=
t
> of the cup at 23 seconds - 30 sec is ok.
>
> If the slip seems to get thicker- in all likelihood you have over
> flocculated, and Need to add more clay.
>
>
> Hope this helps.
>
> John Rodgers
>
> Chelses
>
>
> John Rodgers
> Clayartist and Moldmaker
> 88'GL VW Bus Driver
> Chelsea, AL
> Http://www.moldhaus.com
>
>
>
>
> Susan Hirsch wrote:
>
>> Hi everyone! This is my first time posting anything. I have gotten som=
e
>> great information on here reading the archives, and I'm desperate right
>> now
>> so I'm hoping somebody who knows more about this than I do can help me. =
I
>> will set up a shrine in my house to anyone who can advise me how to fix
>> this
>> lumpy, gelatinous batch of slip!
>>
>> The recipe itself is perfectly respectable, and is not at fault, but I'm
>> posting it here in case it provides you any insight into what can be don=
e
>> to
>> fix my batch. It's Wally's Wonderslip from Cushing's Handbook, as
>> follows:
>>
>> Custer Feldspar 26
>> Whiting 1
>> Goldart 21
>> Tenn. Ball Clay 10
>> EPK 12 Flint 30
>>
>> plus:
>>
>> Water 35%
>> Sodium Silicate 198.5ml/100lbs
>> Darvan #7 198.5ml/100lbs
>>
>>
>> I can't afford a proper slip mixer, so I'm using a 33 gallon garbage bin
>> on
>> wheels. My first mistake was adding the dry ingredients first (I was
>> mindlessly following directions for mixing clay in a huge mixer we had a=
t
>> KCAI). So that caused a lot of trouble getting all the dry clay
>> (especially
>> the ball clay, I'm guessing) off the bottom.
>> I tried using a paint mixer on my drill (HA!) which broke in about 5
>> minutes. Then I rented a bigger better drill and tried to use a mortar
>> mixing attachment. Well, that worked alright until the motor started
>> smoking, so I stopped that quickly. Then I rented a 3/4" drill (two, or
>> three handed dealy...about the biggest you can get) with one speed which
>> was
>> so strong it whipped all kinds of air into the batch...but it broke up t=
he
>> chunks so I kept it up hoping the air would eventually work its way out
>> (if
>> anyone could comment on that I would appreciate it. I'm not sure if I'm
>> being completely foolish thinking that this air might eventually be able
>> to
>> be removed somehow.)
>> It was all smooth, for a while, except for the air bubbles. So I left i=
t
>> to
>> sit for a few days, stirring it occasionally. It seemed to be getting
>> thicker, so I added more water, so that the total was about 50 lbs inste=
ad
>> of 35. And I only added the amount of deflocculent for 100 lbs of clay
>> (because I'm assuming it means for the 100 lbs dry clay?)
>> There is a large gap between the surface of the slip and the lid of the
>> bin,
>> and that might be the major cause of the coagulation on the top. But it
>> seems like more than just drying out...it seems to be gelling up on the
>> top
>> 4 inches or so, which means I should add more deflocculent, right? And
>> it's
>> settling out on the bottom too. I just wanted some more experienced
>> opinions on this before I over-do the deflocculent. I've already gone w=
ay
>> beyond my budget; I'd hate to have to pitch $200 worth of slip and work
>> now.
>> I would really appreciate any tips to save this batch you can give me!
>> Thank you!!!
>>
>> ~Susan
>>
>>
>>
>>
>
>
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