David Martin Hershey on fri 12 sep 08
Hi John & Gayle,
John, I've been playing around with the b-mix slip that we talked about
a while back. While it's not as problematic as regular b-mix, it still
has it's issues. But I still love it's color response with my "floating
waterfall blue".
My cast pieces have a very uniform casting thickness. And I can't see
how much mechanical stress could be imparted to the pieces- except maybe
in the drying. But my sea turtle pieces, which have a large flat
unglazed back, have been cracking in the glaze firing at a rate of about
30% or more.
http://www.dmhstudio.com/G_turtleL_Bkg_L3.html
http://www.dmhstudio.com/G_turtleL_Bkg_L4.html
I've never had one crack in that way when cast in the other 3 clays I
use. This is even with very careful handling, slow drying on hardi
backer, etc.
I'm beginning to think that it may be a porcelain like response where
they are plucking slightly- just enough to cause cracking in a larger
base. (My cracks are not true s cracks- more like what you are
describing.) Certainly b-mix slip shrinks in the glaze firing as much as
porcelain.
It might be worth trying alumina or something under these things on the
shelf?
I'm also going to try blends of b-mix slip and 965 stoneware slip, to
see if I can retain the nice golden breaking color response, but have
the good working properties of the 965. The 965 does tend to break
towards gold with some of my glazes already.
Best, DMH
David Martin Hershey
DMH Studio + Design
2629 Manhattan Ave #137
Hermosa Beach CA USA
90254-2447 310.379.6890
http://www.dmhstudio.com/
John Rodgers wrote:
> It was indeed!! And thereby hangs the tale. The stuff is notorious for
> cracking - especially S cracks.But if you want to use it you just gotta
> deal with it. And I do like ot use it.
>
> John
>
> David Martin Hershey wrote:
>> John, let me guess: was it B-mix? ;^(
James F on sat 13 sep 08
> Hi John & Gayle=2C
>=20
> John=2C I've been playing around with the b-mix slip that we talked about
> a while back. While it's not as problematic as regular b-mix=2C it still
> has it's issues. But I still love it's color response with my "floating
> waterfall blue".
>=20
>=20
> John Rodgers wrote:
> > It was indeed!! And thereby hangs the tale. The stuff is notorious for
> > cracking - especially S cracks.But if you want to use it you just gotta
> > deal with it. And I do like ot use it.
> >
At the risk of sounding like a commercial=2C if you have the opportunity to=
try Rovin's RO-01 "You Betcha Mix" you may have the answer to your problem=
s with B-Mix (www.rovinceramics.com). It is a b-mix-like porcelainous stone=
ware=2C and the stuff is amazing to work with. It is a dream to throw and =
even better for hand building. Unlike the cone 5 b-mix I tried=2C the You =
Betcha seems to have much more structure. It is rated at cone 6-10=2C but =
I have used it as low as 06 and as high as cone 15. You can abuse the heck=
out if it while throwing=2C and it stands up to tons of water without slum=
ping. It does fight you a bit when bellying out the form on the wheel=2C b=
eing described as "rubbery" by a friend who is a production porcelain potte=
r (sorry for the alliteration!)=2C but with my very tight throwing style I =
personally find this to be an advantage.
I have had no problems at all with it up to cone 12. At cone 15 (wood fire=
d) all of the vase and jar type forms were just fine=2C but a stack of slab=
-formed platters fired upside-down warped badly (I also learned that you ca=
n't use seashells as wads at cone 15!). On the downside=2C the bare clay i=
s not exceptional on it's own in salt=2C coming out an even but boring oran=
gepeel grey=2C but this is of course a personal aesthetic judgement. I hav=
e also had no luck with it in place of porcelain with crystalline glazes. =
I have yet to try it in raku=2C but plan to do so if I can find the time to=
build my kiln.
I buy it wet=2C but they will also sell it as a dry mix if you want to save=
on shipping costs.
All the best.
...James
_________________________________________________________________
See how Windows Mobile brings your life together=97at home=2C work=2C or on=
the go.
http://clk.atdmt.com/MRT/go/msnnkwxp1020093182mrt/direct/01/=
David Martin Hershey on wed 17 sep 08
Hi May,
B-mix is problematic as a slip. I spoke with Joe Koons at Laguna Clay
about it, and he says their formula is slightly different for the slip.
It seems that way to me, as the color of the slip is more gray than the
regular b-mix, which has a yellow tone.
Joe also said that it is very hard to deflocculate properly, and that's
why they only offer it as a special order mix, or dry. The slip I get
from them has already jelled a week after manufacture, and I adjust it
for specific gravity with water, and Darvan 7 for viscosity (flow).
I think John is right that the slip has more ball clay in it. You could
try adding small amounts to your scrap mix. I don't think you should add
more than about 30% water by weight to get the correct specific gravity.
A tiny bit more is ok, but use the Darvan to get it to flow. (Or sodium
silicate) 40%+ water is probably causing your shrinkage problems.
Here is Laguna's instructions for mixing slip re: specific gravity in
particular. You don't need to buy anything to measure the weight. Just
use a small container to measure your water and slip weight.
http://www.lagunaclay.com/catalog/pdf/lcc_artslip.pdf
As far as flow goes, I've had better results with deflocculating it more
to the thin side. Just don't go too far, or it will jell, never to return...
I think adding scrap to another slip (like Laguna 830d or 829d) would
work for cone 8/9, but you would still have to adjust for specific
gravity and viscosity.
Talk to John Rogers on the list about b-mix slip. He is the resident
expert. Following are John's instructions on slip mixing.
Best, DMH
David Martin Hershey
DMH Studio + Design
2629 Manhattan Ave #137
Hermosa Beach CA USA
90254-2447 310.379.6890
http://www.dmhstudio.com/
>John Rogers wrote:
I do a lot of slip casting. Here are a few pointers.
Go to the Laguna Clay website and download their instructions on how to
mix slip. Their procedures pretty much cover most slips, no matter the
formula. Particularly the ratio of water to clay. Once you have the clay
mixed into the water you will want to adjust the density and the viscosity.
To test the density weight a pint of water and a pint of slip.Divide the
weight of the water into the weight of the slip. You will get a number
like 1.5 or 1.8 or something similar. If the number is less than 1.75
you don't have enough clay in the mix. It it is above 1.85 you have too
much clay in the mix so you need to add some water. The best numbers to
work with is that range anywhere between 1.75 and 1.85. I usually start
at 1.75 and as I do casting, the water loss in the reclaimed clay will
slowly change the number to 1.85, then I add some water.
To test the viscosity you need a viscosity cup. I strongly recommend the
one that new Mexico Clay sells that is really a paint tester. It only
costs $4.95 and does an excellent job, is easy to clean up, and is very
fast. The old business of using a two-hole stopper, an Erlenmeyer flask
and glass tubing is bogus - takes forever and they charge like $25 for
glass and more for plastic. Use the New Mexico Clay viscosity cup. It
has a tiny hole in the bottom, and if the slip is adjusted properly the
cup filled with slip will drain in 23 seconds. Slower than that and you
need to add some Sodium Silicate. You have to be careful with any
adjustments because just the right amount will make the clay flow very
easily. To much and it will become more viscous and won't drain, or will
do so very slowly. Once you have over done it with silicate, you must
add more clay and re-adjust the density, then re- adjust the silicate.
If you were to plot viscosity vs silicate it would plot in a graph
shaped like a "U" As you add silicate, the viscosity decreases and the
flow rate goes up. At Exactly the right amount. all the numbers will be
at the very bottom of the "U". As more silicate is added, the viscosity
increases, the flow rate slows, and the numbers move up the leg of the
"U". When that happens you are in trouble. Big adjustments in the amount
of clay have to be made.
So - First- Adjust the density. Second - adjust the viscosity. - Always
in that order.
Regards mixing your slip, a power mixer is recommended, and a long
mixing period for fresh slip is recommended. I finally went so far as to
buy a 33 gallon slip mixing tank. Best investment I have made in a long
time. Makes it so easy to mix slip, recover reclaimed clay, and adjust
the density and viscosity. I recommend it.
May Luk wrote:
> Hello David;
>
> I fired B-mix to cone 8/9. I get small chipping on the foot once a while. It does behave wee bit like porcelain compare with other stoneware clay.
>
> I learned from Marcia S. here on Clayart to fire porcelain slabs resting on small clay rods. I don't have an extruder, so I hand-rolled mine with grogged stoneware clay. I only used them a couple of times. It seems to work. If you look up the archive, you can find better explanation of how it works.
>
> Can I ask a question on b-mix slip cast? I've been reading the archive (mainly John Roger's posts) and I found that B-mix scrap is not good for making slip cast. I have a lot of leftover dried up B-mix scrap from handbuilding and I want to use up the leftover to make small slip cast cups to fill the kiln and be part of my reclaim workflow.
>
> I have been having such problem with the slip. It shrinks unevenly, it wants to takes more than 40% of water, it thicken up after a week while it worked perfectly the week before. It's a mess! I cannot order dry B-mix clay at where I am. I am thinking of mixing my own recipe from scratch and put in perhaps 25% B-mix scrap and see how it goes. I have never learned how to mix clay. (except I made 1 kg of porcelain, that's all) Mixing is easy, but how to test if it's right for the job?
>
> I make slip for paining. The B-mix slip gels up just adding water, unlike any slip I have worked with.
>
>
>
John Rodgers on wed 17 sep 08
David,
I use a lot of B-mix slip as well. The throwing B-mix and the casting
B-mix are very similar. I think the only real difference is in the
amount of ball clay that is present. I like the combination of the two
because you can mix and match pieces and parts and in the firings they
come out fine - except for that occasional crack.- mostly in the bottoms
of thrown forms.
A couple of things finally sold me on sticking to B-mix rather than
using porcelain which I also like very much -
(1) B-mix - both throwing and slip clay - takes my Floating Blue
beautifully. It nearly always turns out wonderfully.
(2) I can fire the B-mix directly on a shelf with no shelf coatings of
any kind. The B-mix does not stick at the Temps I fire (cone 5 to
5-1/2) I will at times spread a bit of Alumina Hydrate around when I am
firing plates - which I fire sitting on the foot ring, but for the most
part - no kiln wash. I virtually never have glaze runs, primarily
because I have been at it long enough to have a palette of glazes that I
like, that work for me, and that is what I stick with, rarely
experimenting with other glazes. That is what works for me. Others would
be bored silly, I know - and I understand. But I am a semi production
person and I don't want to spend a lot of time and materials messing around.
Regards,
John Rodgers
Chelsea, AL
David Martin Hershey wrote:
> Hi John & Gayle,
>
> John, I've been playing around with the b-mix slip that we talked about
> a while back. While it's not as problematic as regular b-mix, it still
> has it's issues. But I still love it's color response with my "floating
> waterfall blue".
>
> My cast pieces have a very uniform casting thickness. And I can't see
> how much mechanical stress could be imparted to the pieces- except maybe
> in the drying. But my sea turtle pieces, which have a large flat
> unglazed back, have been cracking in the glaze firing at a rate of about
> 30% or more.
> http://www.dmhstudio.com/G_turtleL_Bkg_L3.html
> http://www.dmhstudio.com/G_turtleL_Bkg_L4.html
>
> I've never had one crack in that way when cast in the other 3 clays I
> use. This is even with very careful handling, slow drying on hardi
> backer, etc.
>
> I'm beginning to think that it may be a porcelain like response where
> they are plucking slightly- just enough to cause cracking in a larger
> base. (My cracks are not true s cracks- more like what you are
> describing.) Certainly b-mix slip shrinks in the glaze firing as much as
> porcelain.
>
> It might be worth trying alumina or something under these things on the
> shelf?
>
> I'm also going to try blends of b-mix slip and 965 stoneware slip, to
> see if I can retain the nice golden breaking color response, but have
> the good working properties of the 965. The 965 does tend to break
> towards gold with some of my glazes already.
>
> Best, DMH
>
> David Martin Hershey
> DMH Studio + Design
> 2629 Manhattan Ave #137
> Hermosa Beach CA USA
> 90254-2447 310.379.6890
> http://www.dmhstudio.com/
>
> John Rodgers wrote:
>> It was indeed!! And thereby hangs the tale. The stuff is notorious for
>> cracking - especially S cracks.But if you want to use it you just gotta
>> deal with it. And I do like ot use it.
>>
>> John
>>
>> David Martin Hershey wrote:
>>> John, let me guess: was it B-mix? ;^(
>
>
May Luk on thu 18 sep 08
Hello David;
I fired B-mix to cone 8/9. I get small chipping on the foot once a while. I=
t does behave wee bit like porcelain compare with other stoneware clay.
I learned from Marcia S. here on Clayart to fire porcelain slabs resting on=
small clay rods. I don't have an extruder, so I hand-rolled mine with grog=
ged stoneware clay. I only used them a couple of times. It seems to work. I=
f you look up the archive, you can find better explanation of how it works.=
=20
Can I ask a question on b-mix slip cast? I've been reading the archive (mai=
nly John Roger's posts) and I found that B-mix scrap is not good for making=
slip cast. I have a lot of leftover dried up B-mix scrap from handbuilding=
and I want to use up the leftover to make small slip cast cups to fill the=
kiln and be part of my reclaim workflow.=20
I have been having such problem with the slip. It shrinks unevenly, it want=
s to takes more than 40% of water, it thicken up after a week while it work=
ed perfectly the week before. It's a mess! I cannot order dry B-mix clay at=
where I am. I am thinking of mixing my own recipe from scratch and put in =
perhaps 25% B-mix scrap and see how it goes. I have never learned how to mi=
x clay. (except I made 1 kg of porcelain, that's all) Mixing is easy, but h=
ow to test if it's right for the job?=20
I make slip for paining. The B-mix slip gels up just adding water, unlike a=
ny slip I have worked with.=20
Thank you in advance for your insights
May
Brooklyn NY
[...]
> > I'm beginning to think that it may be a porcelain
> like response where
> > they are plucking slightly- just enough to cause
> cracking in a larger
> > base. (My cracks are not true s cracks- more like what
> you are
> > describing.) Certainly b-mix slip shrinks in the glaze
> firing as much as
> > porcelain.
> >
> > It might be worth trying alumina or something under
> these things on the
> > shelf?
> >
> > I'm also going to try blends of b-mix slip and 965
> stoneware slip, to
> > see if I can retain the nice golden breaking color
> response, but have
> > the good working properties of the 965. The 965 does
> tend to break
> > towards gold with some of my glazes already.
> >
> > Best, DMH
> >
=0A=0A=0A
May Luk on fri 19 sep 08
Thanks David;
I have closed read on all the notes from Clayart, as well as the page from =
the Laguna site. *sigh*
B-mix slip probably be very good for slip trailing, cause it's so thick on =
it own. It's hard not (wanting) to put more water. even 40% H2O, the clay i=
s thick like whip cream.
Likely I have to switch clay. That's all.
Apology to John. I had mis-spelt his last name Roger. It's Rodger. I though=
t it was too short after I sent out the email. The problem of internet - I =
never have to say him name out loud.
Thanks again
May
Brooklyn NY
--- On Thu, 18/9/08, David Martin Hershey wrote:
> From: David Martin Hershey
> Subject: Re: Crack Repair in Bisque Pot Bottom, now b-mix cracking
> To: CLAYART@LSV.CERAMICS.ORG
> Date: Thursday, 18 September, 2008, 5:25 AM
> Hi May,
>=20
> B-mix is problematic as a slip. I spoke with Joe Koons at
> Laguna Clay
> about it, and he says their formula is slightly different
> for the slip.
>=20
> It seems that way to me, as the color of the slip is more
> gray than the
> regular b-mix, which has a yellow tone.
>=20
> Joe also said that it is very hard to deflocculate
> properly, and that's
> why they only offer it as a special order mix, or dry. The
> slip I get
> from them has already jelled a week after manufacture, and
> I adjust it
> for specific gravity with water, and Darvan 7 for viscosity
> (flow).
>=20
> I think John is right that the slip has more ball clay in
> it. You could
> try adding small amounts to your scrap mix. I don't
> think you should add
> more than about 30% water by weight to get the correct
> specific gravity.
> A tiny bit more is ok, but use the Darvan to get it to
> flow. (Or sodium
> silicate) 40%+ water is probably causing your shrinkage
> problems.
>=20
> Here is Laguna's instructions for mixing slip re:
> specific gravity in
> particular. You don't need to buy anything to measure
> the weight. Just
> use a small container to measure your water and slip
> weight.
> http://www.lagunaclay.com/catalog/pdf/lcc_artslip.pdf
>=20
> As far as flow goes, I've had better results with
> deflocculating it more
> to the thin side. Just don't go too far, or it will
> jell, never to return...
>=20
> I think adding scrap to another slip (like Laguna 830d or
> 829d) would
> work for cone 8/9, but you would still have to adjust for
> specific
> gravity and viscosity.
>=20
> Talk to John Rogers on the list about b-mix slip. He is the
> resident
> expert. Following are John's instructions on slip
> mixing.
>=20
> Best, DMH
>=20
> David Martin Hershey
> DMH Studio + Design
> 2629 Manhattan Ave #137
> Hermosa Beach CA USA
> 90254-2447 310.379.6890
> http://www.dmhstudio.com/
>=20
> >John Rogers wrote:
>=20
> I do a lot of slip casting. Here are a few pointers.
>=20
> Go to the Laguna Clay website and download their
> instructions on how to
> mix slip. Their procedures pretty much cover most slips, no
> matter the
> formula. Particularly the ratio of water to clay. Once you
> have the clay
> mixed into the water you will want to adjust the density
> and the viscosity.
>=20
> To test the density weight a pint of water and a pint of
> slip.Divide the
> weight of the water into the weight of the slip. You will
> get a number
> like 1.5 or 1.8 or something similar. If the number is less
> than 1.75
> you don't have enough clay in the mix. It it is above
> 1.85 you have too
> much clay in the mix so you need to add some water. The
> best numbers to
> work with is that range anywhere between 1.75 and 1.85. I
> usually start
> at 1.75 and as I do casting, the water loss in the
> reclaimed clay will
> slowly change the number to 1.85, then I add some water.
>=20
> To test the viscosity you need a viscosity cup. I strongly
> recommend the
> one that new Mexico Clay sells that is really a paint
> tester. It only
> costs $4.95 and does an excellent job, is easy to clean up,
> and is very
> fast. The old business of using a two-hole stopper, an
> Erlenmeyer flask
> and glass tubing is bogus - takes forever and they charge
> like $25 for
> glass and more for plastic. Use the New Mexico Clay
> viscosity cup. It
> has a tiny hole in the bottom, and if the slip is adjusted
> properly the
> cup filled with slip will drain in 23 seconds. Slower than
> that and you
> need to add some Sodium Silicate. You have to be careful
> with any
> adjustments because just the right amount will make the
> clay flow very
> easily. To much and it will become more viscous and
> won't drain, or will
> do so very slowly. Once you have over done it with
> silicate, you must
> add more clay and re-adjust the density, then re- adjust
> the silicate.
>=20
> If you were to plot viscosity vs silicate it would plot in
> a graph
> shaped like a "U" As you add silicate, the
> viscosity decreases and the
> flow rate goes up. At Exactly the right amount. all the
> numbers will be
> at the very bottom of the "U". As more silicate
> is added, the viscosity
> increases, the flow rate slows, and the numbers move up the
> leg of the
> "U". When that happens you are in trouble. Big
> adjustments in the amount
> of clay have to be made.
>=20
> So - First- Adjust the density. Second - adjust the
> viscosity. - Always
> in that order.
>=20
> Regards mixing your slip, a power mixer is recommended, and
> a long
> mixing period for fresh slip is recommended. I finally went
> so far as to
> buy a 33 gallon slip mixing tank. Best investment I have
> made in a long
> time. Makes it so easy to mix slip, recover reclaimed clay,
> and adjust
> the density and viscosity. I recommend it.
>=20
> May Luk wrote:
> > Hello David;
> >
> > I fired B-mix to cone 8/9. I get small chipping on the
> foot once a while. It does behave wee bit like porcelain
> compare with other stoneware clay.
> >
> > I learned from Marcia S. here on Clayart to fire
> porcelain slabs resting on small clay rods. I don't have
> an extruder, so I hand-rolled mine with grogged stoneware
> clay. I only used them a couple of times. It seems to work.
> If you look up the archive, you can find better explanation
> of how it works.
> >
> > Can I ask a question on b-mix slip cast? I've been
> reading the archive (mainly John Roger's posts) and I
> found that B-mix scrap is not good for making slip cast. I
> have a lot of leftover dried up B-mix scrap from
> handbuilding and I want to use up the leftover to make small
> slip cast cups to fill the kiln and be part of my reclaim
> workflow.
> >
> > I have been having such problem with the slip. It
> shrinks unevenly, it wants to takes more than 40% of water,
> it thicken up after a week while it worked perfectly the
> week before. It's a mess! I cannot order dry B-mix clay
> at where I am. I am thinking of mixing my own recipe from
> scratch and put in perhaps 25% B-mix scrap and see how it
> goes. I have never learned how to mix clay. (except I made 1
> kg of porcelain, that's all) Mixing is easy, but how to
> test if it's right for the job?
> >
> > I make slip for paining. The B-mix slip gels up just
> adding water, unlike any slip I have worked with.
> >
> >
> >=0A=0A=0A
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