John Post on tue 28 mar 06
Here's some things I have learned about iron reds...
Iron reds like a slow cool. The iron crystals precipitate to the
surface during the slow cooling.
That is why many times if you refire the iron reds in a bisque firing
they come out redder. They spend more time in the temperature range
where the iron crystals develop on the surface of the glaze.
I fire my glaze kiln with the following schedule and get nice bright
iron reds...
270 degrees F an hour up to 2132
100 degrees F an hour up to 2222 hold here for 15 minutes
drop at full speed to 1800 degrees F and hold here for one hour
drop at 125 degrees F per hour until 1300 degrees
let the kiln cool on its own from there
I have also learned in my experiments that the faster you cool an iron
red, the more iron you need in the glaze to get a red surface. So if
you slow cool an iron red glaze, often you can get a nicer red with less
iron in the glaze.
It also helps to have shelves close to iron red works, I rarely get good
iron reds on the top shelf of my electric kiln.
They develop best with a shelf above them that acts as a big heat sink
and helps to cool the ware more slowly.
So if you are trying to duplicate getting that nice iron red on your
currie grid, make more grids and fire them with different cooling
cycles. My cooling cycle matches my glazes. I had to develop an iron
red that would fire to a nice red during the same kiln loads as my
normal calcium matte glazes. I used the currie grid to find one that
worked for me.
Good luck with your testing and firing.
John Post
Sterling Heights, Michigan
Jorge Nabel on tue 28 mar 06
This is my third attempt to get your attention into this subject
> Clayarters, I already sent this post, but was advised to re send it
> after NCECA-
> After a Currie grid , we got a bunch of Iron Saturate ^6 glazes
> Electric (ox)
> They range from caramel to metalic grey,to black.
> We refired some of them to bisque (1000C)and those closer to corner C
> turned yellow.
> Some changed from black to brown. But, in the only one firing we have
> no records of,
> when refired they turned a gorgeous RED. Of course it never happened
> again.
> Since this happened, some months ago, I have read archives, hammer,
> some other books
> concernig iron cristals,etc,but couldnt duplicate the red.
> Corner C is Nepheline, high alkaline frit and 20%dolomite. plus 15%RIO
> Someone says it depends on fast first firing with enough heat, others
> say go slowly up,
> and so on. I also tried the thin vs thick issue,but with no result
> I began to learn some chemistry in order to understand. But so far, no
> clue.
> Anyone has experienced this?
> I try to make clear that Im trying to understand Why it turned RED,to
> replicate the firing
> Thanks, Jorge en Buenos Aires
Des & Jan Howard on wed 29 mar 06
Jorge
You have asked some questions, you have been given some possibilities.
Now its your turn to tell us what you tried & how the tests went.
I guarantee further discussion will follow.
Des
Jorge Nabel wrote:
> This is my third attempt to get your attention into this subject
>
>> Clayarters, I already sent this post, but was advised to re send it
>> after NCECA-
>> After a Currie grid , we got a bunch of Iron Saturate ^6 glazes
>> Electric (ox)
>> They range from caramel to metalic grey,to black.
>> We refired some of them to bisque (1000C)and those closer to corner C
>> turned yellow.
>> Some changed from black to brown. But, in the only one firing we have
>> no records of,
>> when refired they turned a gorgeous RED. Of course it never happened
>> again.
>> Since this happened, some months ago, I have read archives, hammer,
>> some other books
>> concernig iron cristals,etc,but couldnt duplicate the red.
>> Corner C is Nepheline, high alkaline frit and 20%dolomite. plus 15%RIO
>> Someone says it depends on fast first firing with enough heat, others
>> say go slowly up,
>> and so on. I also tried the thin vs thick issue,but with no result
>> I began to learn some chemistry in order to understand. But so far, no
>> clue.
>> Anyone has experienced this?
>> I try to make clear that Im trying to understand Why it turned RED,to
>> replicate the firing
>>
--
Des & Jan Howard
Lue Pottery
LUE NSW 2850
Australia
Ph/Fax 02 6373 6419
http://www.luepottery.hwy.com.au
John Hesselberth on wed 29 mar 06
On Mar 28, 2006, at 8:13 PM, John Post wrote:
> So if you are trying to duplicate getting that nice iron red on your
> currie grid, make more grids and fire them with different cooling
> cycles. My cooling cycle matches my glazes.
If you do this it can make a huge difference whether the grid is
laying flat on the kiln shelf or is propped up against the side. The
one laying flat will cool more slowly because of the mass of the kiln
shelf.
Regards,
John
Jorge Nabel on thu 30 mar 06
Des , what I wrote were the test I already made with no luck.
I glazed two sets of pots, and fired them in different kilns
with a different climbing rate. One was a slow one (about 30C/hour final)
and another was fast ( about 80C/hour) Then refired them in a
bisque firing together.Result, yellow
I also observed that the red appeared where thin,so i glazed thin.
Only the first time gave red. And never again.
If I get a clue ,Ill inform.
Jorge en Buenos Aires
Jorge
You have asked some questions, you have been given some possibilities.
Now its your turn to tell us what you tried & how the tests went.
I guarantee further discussion will follow.
Des
Jorge Nabel wrote:
> > This is my third attempt to get your attention into this subject
> >
>
>> >> Clayarters, I already sent this post, but was advised to re send it
>> >> after NCECA-
>> >> After a Currie grid , we got a bunch of Iron Saturate ^6 glazes
>> >> Electric (ox)
>> >> They range from caramel to metalic grey,to black.
>> >> We refired some of them to bisque (1000C)and those closer to corner C
>> >> turned yellow.
>> >> Some changed from black to brown. But, in the only one firing we have
>> >> no records of,
>> >> when refired they turned a gorgeous RED. Of course it never happened
>> >> again.
>> >> Since this happened, some months ago, I have read archives, hammer,
>> >> some other books
>> >> concernig iron cristals,etc,but couldnt duplicate the red.
>> >> Corner C is Nepheline, high alkaline frit and 20%dolomite. plus 15%RIO
>> >> Someone says it depends on fast first firing with enough heat, others
>> >> say go slowly up,
>> >> and so on. I also tried the thin vs thick issue,but with no result
>> >> I began to learn some chemistry in order to understand. But so far, no
>> >> clue.
>> >> Anyone has experienced this?
>> >> I try to make clear that Im trying to understand Why it turned RED,to
>> >> replicate the firing
>> >>
>>
Donna Kat on fri 31 mar 06
Have you posted this glaze recipe? I have not been able to track it down if
you have. The fact that you say it has only been red one time where applied
thinly makes me think it is more like Nutmeg than Toby's (Randy's) Red - in
which case are you sure it was really as thin in subsequent glazing as when
you got the red color you want? Glaze does evaporate and unless you are
keeping an eye on the density will go on thicker over time. Sorry if I am
stating the obvious to you. If I am not, I would suggest taking a small
amount, thinning it down with water to thin cream consistency, do a real
quick dip and see what that looks like.
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