Veena Raghavan on sun 5 sep 04
Someone recently asked about a Magic Black that they had seen but could n=
ot
recall where. I just looked through the Sept-Oct 04 issue of Clay Times,
and there is a Magic Black by Sequoia Miller on Page 63.
Hope this helps.
Veena
Veena Raghavan
75124.2520@compuserve.com
Scott Paulding on tue 7 sep 04
My answer to your questions is "That's why they call it Magic" :)
-scott
--- daniel wrote:
> Hi John, all,
>
> This glaze intrigued me. Its got two feldspars and two sources of MgO. I
> see that the two spars pretty much result in a balance of the NaO and the
> K2O. Other than that I wasn't sure why this might be a good way to go. The
> talc and the dolomite was unusual to me too.Are two MgO sources really
> required ?
>
> So, it seems that this could be formulated differently. I'll probably try
> it out. So any idea as to why two spars and two MgO sources ? Also, I note
> that the black is based on RIO and Chrome, but not that much iron. Does this
> produce a really good black, or does it vary at all ? Perhaps the MgO has an
> impact on the iron causing it to darken here.
>
> There is a lot of MgO in this so I'm guessing that this has a nice feel to
> it. I guess it could lose some gloss if cooled slowly. It also seems that
> while it should be a gloss it seems shy of silica and alumina, for cone 10.
> Does this glaze move much at cone 10 or does the high MgO help it out ?
>
> So there you go, I've been to a glaze class and now all I do is ask
> questions. Is anyone familiar with this glaze and would like to comment on
> the above for me ? I think I'll try it out and test a variation or two. Mind
> you I expect it'll craze on my porcelains. I'll probably have to sub Kona
> for the NC-4 unless there's a reason to keep it.
>
>
> > The Magic Black in the Clay Times is also known as :
> >
> > CUSHING BLACK Cone 10
> >
> >
> > Custer Feldspar 20.00
> > NC-4 Soda Feldspar 20.00
> > Whiting 2.00
> > Silica 20.00
> > Kentucky Old Mine #4 10.00
> > Talc Westalc 35 13.00
> > Dolomite 15.00
> >
> > Chrome Oxide 1.00
> > Red Iron Oxide 3.00
> >
>
> Thanx
> D
>
> Belmont, California, USA
> (ex terra australis)
>
>
______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
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>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
=====
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-Albert Einstein
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John Britt on tue 7 sep 04
The Magic Black in the Clay Times is also known as :
CUSHING BLACK Cone 10
Custer Feldspar 20.00
NC-4 Soda Feldspar 20.00
Whiting 2.00
Silica 20.00
Kentucky Old Mine #4 10.00
Talc Westalc 35 13.00
Dolomite 15.00
Chrome Oxide 1.00
Red Iron Oxide 3.00
Hope that helps,
John Britt
www.johnbrittpottery.com
daniel on tue 7 sep 04
Hi John, all,
This glaze intrigued me. Its got two feldspars and two sources of MgO. I
see that the two spars pretty much result in a balance of the NaO and the
K2O. Other than that I wasn't sure why this might be a good way to go. The
talc and the dolomite was unusual to me too.Are two MgO sources really
required ?
So, it seems that this could be formulated differently. I'll probably try
it out. So any idea as to why two spars and two MgO sources ? Also, I note
that the black is based on RIO and Chrome, but not that much iron. Does this
produce a really good black, or does it vary at all ? Perhaps the MgO has an
impact on the iron causing it to darken here.
There is a lot of MgO in this so I'm guessing that this has a nice feel to
it. I guess it could lose some gloss if cooled slowly. It also seems that
while it should be a gloss it seems shy of silica and alumina, for cone 10.
Does this glaze move much at cone 10 or does the high MgO help it out ?
So there you go, I've been to a glaze class and now all I do is ask
questions. Is anyone familiar with this glaze and would like to comment on
the above for me ? I think I'll try it out and test a variation or two. Mind
you I expect it'll craze on my porcelains. I'll probably have to sub Kona
for the NC-4 unless there's a reason to keep it.
> The Magic Black in the Clay Times is also known as :
>
> CUSHING BLACK Cone 10
>
>
> Custer Feldspar 20.00
> NC-4 Soda Feldspar 20.00
> Whiting 2.00
> Silica 20.00
> Kentucky Old Mine #4 10.00
> Talc Westalc 35 13.00
> Dolomite 15.00
>
> Chrome Oxide 1.00
> Red Iron Oxide 3.00
>
Thanx
D
Belmont, California, USA
(ex terra australis)
Anne Wellings on wed 8 sep 04
On Tue, 7 Sep 2004 23:13:12 -0400, daniel wrote:
> There is a lot of MgO in this so I'm guessing that this has a nice feel to
>it. I guess it could lose some gloss if cooled slowly. It also seems that
>while it should be a gloss it seems shy of silica and alumina, for cone 10.
>Does this glaze move much at cone 10 or does the high MgO help it out ?
>
> So there you go, I've been to a glaze class and now all I do is ask
>questions. Is anyone familiar with this glaze and would like to comment on
>the above for me ? I think I'll try it out and test a variation or two.
Several years ago, I worked in a studio with Sequoia Miller, who was
mentioned in connection with the Magic Black recipe in Clay Times. I
remember the glaze as more of a matte or semi-matte than as a gloss. Yet it
seems it could run if on too thick, or maybe in combo with certain other
glazes. I also remember it had some tendency toward cratering, I think
mainly if placed too near a flame, so we tried to put it more in the middle
of a shelf. The kiln we fired it in was a 24 cu. ft. Olsen updraft. I
didn't see the Clay Times issue, but sometimes run into Sequoia around town
and will mention to him that people were discussing this.
Anne Wellings
Sunrise Beach Pottery
Olympia, WA
Anne Wellings on wed 8 sep 04
On Tue, 7 Sep 2004 23:13:12 -0400, daniel wrote:
Does this
>produce a really good black, or does it vary at all ? Perhaps the MgO has
an
>impact on the iron causing it to darken here.
>
I forgot to answer this part of the questions. I remember it as having a
sort of gun-metal finish which gave it a sort of grey haze over the black.
But I would still call it black as opposed to brownish or greenish.
I'm not the one to answer the more technical questions about the
composition of this glaze.
Anne
Ron Roy on fri 10 sep 04
Hi Daniel,
This may not be a stable glaze - I would recommend you have it tested for
chrome release before using it as a liner.
Chrome oxide has some toxicity concerns - and the chrome will volitailize -
any other glazes with tin in them will get flashed with pink - the chrome
will also reside in the kiln itself as well - tainting any glazes that have
tin in them.
Because chrome in volitile it also means all the ware in the kiln will get
a coating of chrome - how much and would it be significant? I don't know.
Yes it is oversupplied with MgO and yes I think you can reformulate using
less materials - and get the same glaze.
RR
> This glaze intrigued me. Its got two feldspars and two sources of MgO. I
>see that the two spars pretty much result in a balance of the NaO and the
>K2O. Other than that I wasn't sure why this might be a good way to go. The
>talc and the dolomite was unusual to me too.Are two MgO sources really
>required ?
>
> So, it seems that this could be formulated differently. I'll probably try
>it out. So any idea as to why two spars and two MgO sources ? Also, I note
>that the black is based on RIO and Chrome, but not that much iron. Does this
>produce a really good black, or does it vary at all ? Perhaps the MgO has an
>impact on the iron causing it to darken here.
>
> There is a lot of MgO in this so I'm guessing that this has a nice feel to
>it. I guess it could lose some gloss if cooled slowly. It also seems that
>while it should be a gloss it seems shy of silica and alumina, for cone 10.
>Does this glaze move much at cone 10 or does the high MgO help it out ?
>
> So there you go, I've been to a glaze class and now all I do is ask
>questions. Is anyone familiar with this glaze and would like to comment on
>the above for me ? I think I'll try it out and test a variation or two. Mind
>you I expect it'll craze on my porcelains. I'll probably have to sub Kona
>for the NC-4 unless there's a reason to keep it.
>
>
>> The Magic Black in the Clay Times is also known as :
>>
>> CUSHING BLACK Cone 10
>>
>>
>> Custer Feldspar 20.00
>> NC-4 Soda Feldspar 20.00
>> Whiting 2.00
>> Silica 20.00
>> Kentucky Old Mine #4 10.00
>> Talc Westalc 35 13.00
>> Dolomite 15.00
>>
>> Chrome Oxide 1.00
>> Red Iron Oxide 3.00
>>
>
>Thanx
>D
>
>Belmont, California, USA
>(ex terra australis)
>
>______________________________________________________________________________
>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.
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
daniel on fri 10 sep 04
Hi Ron,
Thanx for this. I had not considered the volatility of Chrome ox here.
I was mainly interested in the base glaze formulation which seemed more
complex than necessary. I think I'll try out tests but unless its a stella
glaze I'm not likely to pursue it more than to satisfy my curiosity
concerning its composition. As to stability, it would certainly need
testing if I got interested in it..
I have done a couple of versions of it. Seems that F4 is a pretty decent
sub for NC-4. I must look into where these come from, Florida, North
Carolina ? Anyhow, it seems so long as you only care about KNaO in aggregate
that the custer can be removed and the dolomite can be dropped too, given
adjustments elsewhere.
Of course I now have 2 or three tests to do. Will let people know what I
find.
Thanx
D
> Hi Daniel,
>
> This may not be a stable glaze - I would recommend you have it tested for
> chrome release before using it as a liner.
>
> Chrome oxide has some toxicity concerns - and the chrome will volitailize -
> any other glazes with tin in them will get flashed with pink - the chrome
> will also reside in the kiln itself as well - tainting any glazes that have
> tin in them.
>
> Because chrome in volitile it also means all the ware in the kiln will get
> a coating of chrome - how much and would it be significant? I don't know.
>
> Yes it is oversupplied with MgO and yes I think you can reformulate using
> less materials - and get the same glaze.
>
> RR
>
>
>> This glaze intrigued me. Its got two feldspars and two sources of MgO. I
>>see that the two spars pretty much result in a balance of the NaO and the
>>K2O. Other than that I wasn't sure why this might be a good way to go. The
>>talc and the dolomite was unusual to me too.Are two MgO sources really
>>required ?
>>
>> So, it seems that this could be formulated differently. I'll probably try
>>it out. So any idea as to why two spars and two MgO sources ? Also, I note
>>that the black is based on RIO and Chrome, but not that much iron. Does this
>>produce a really good black, or does it vary at all ? Perhaps the MgO has an
>>impact on the iron causing it to darken here.
>>
>> There is a lot of MgO in this so I'm guessing that this has a nice feel to
>>it. I guess it could lose some gloss if cooled slowly. It also seems that
>>while it should be a gloss it seems shy of silica and alumina, for cone 10.
>>Does this glaze move much at cone 10 or does the high MgO help it out ?
>>
>> So there you go, I've been to a glaze class and now all I do is ask
>>questions. Is anyone familiar with this glaze and would like to comment on
>>the above for me ? I think I'll try it out and test a variation or two. Mind
>>you I expect it'll craze on my porcelains. I'll probably have to sub Kona
>>for the NC-4 unless there's a reason to keep it.
>>
>>
>>> The Magic Black in the Clay Times is also known as :
>>>
>>> CUSHING BLACK Cone 10
>>>
>>>
>>> Custer Feldspar 20.00
>>> NC-4 Soda Feldspar 20.00
>>> Whiting 2.00
>>> Silica 20.00
>>> Kentucky Old Mine #4 10.00
>>> Talc Westalc 35 13.00
>>> Dolomite 15.00
>>>
>>> Chrome Oxide 1.00
>>> Red Iron Oxide 3.00
>>>
>>
>>Thanx
>>D
>>
>>Belmont, California, USA
>>(ex terra australis)
>>
>>______________________________________________________________________________
>>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.
>
> Ron Roy
> RR#4
> 15084 Little Lake Road
> Brighton, Ontario
> Canada
> K0K 1H0
> Phone: 613-475-9544
> Fax: 613-475-3513
>
> ______________________________________________________________________________
> 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.
Thanx
D
Belmont, California, USA
(ex terra australis)
Ron Roy on sun 12 sep 04
Hi Daniel,
I think the two soda spars are mined in the same vicinity - when you
compare their analysis you will find them very close.
It is often the case - when a new glaze is made by mixing other glazes -
that you get that sort of duplication. I the days before easy calculation
by computer it was a major job to reformulate and reduce the number of
materials.
Who knows why - it could even be that some materials were in short supply.
I'll bet you will see more melting when redundant materials are used -
because every material brings it's own set of trace materials - which will
help melting. Particle size must also be an issue.
I like the idea of using redundant materials - not only for the additional
melting but for minimizing the influence of material variation.
It is counter productive - I think - to try to make glazes with as few
materials as possible because you increase the effect of material
variation.
That said - I am very interested in your experiments - especially when
results show up that are not expected.
I would also be interested in knowing the effect on colouring oxides - like
copper or iron. I would expect some differences with copper for instance
when shifting the balance of K2O and Na2O.
RR
> Thanx for this. I had not considered the volatility of Chrome ox here.
>
> I was mainly interested in the base glaze formulation which seemed more
>complex than necessary. I think I'll try out tests but unless its a stella
>glaze I'm not likely to pursue it more than to satisfy my curiosity
>concerning its composition. As to stability, it would certainly need
>testing if I got interested in it..
>
> I have done a couple of versions of it. Seems that F4 is a pretty decent
>sub for NC-4. I must look into where these come from, Florida, North
>Carolina ? Anyhow, it seems so long as you only care about KNaO in aggregate
>that the custer can be removed and the dolomite can be dropped too, given
>adjustments elsewhere.
>
> Of course I now have 2 or three tests to do. Will let people know what I
>find.
>
>Thanx
>D
Ron Roy
RR#4
15084 Little Lake Road
Brighton, Ontario
Canada
K0K 1H0
Phone: 613-475-9544
Fax: 613-475-3513
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