John Post on tue 14 dec 10
Below is some information I have on my website about how I approach =3D20
getting iron reds in my electric kilns. I know that there are some on =3D2=
0=3D
this list who are testing iron reds right now so I thought I would =3D20
pass this information on...
There are some recipes on my site too if you are looking for more to =3D20
test.
Make Sure you Slow Cool your Kiln
Iron reds form as the glaze cools. I cool at 150=3DB0 Fahrenheit per hour =
=3D20=3D
from 1800=3DB0 to 1300=3DB0. Try a cooling at 125=3DB0 per hour or 100=3DB0=
per =3D
hour =3D20
if you are having trouble getting reds. Or program in a hold somewhere =3D2=
0=3D
between 1800=3DB0 and 1700=3DB0 and see what happens. The only way to get m=
y =3D
=3D20
glazes to work in your kiln is to do some of the legwork for yourself. =3D2=
0=3D
Try different firing profiles than mine if my schedule is not giving =3D20
you the results you want.
Slow Cooling with a Kiln Sitter
After your kiln sitter drops, lift the latch slowly and press the =3D20
plunger button back in. Then slowly lower the latch so that it does =3D20
not trip the switch and shut off the kiln again. On kilns that have =3D20
low-medium-high switches, try setting the kiln on medium for a few =3D20
hours. On kilns that have a series of simple on-off switches, turn =3D20
half of them off. On the manual kilns I have worked with, these =3D20
strategies have created a slow cool. After a few hours of slow =3D20
cooling, turn your kiln off. If your kiln looks orangey inside it is =3D20
in the 1600-1800=3DB0 range and that is the where iron red glazes need to =
=3D20=3D
spend some time.
Try a line blend
The quicker a kiln cools, the more iron a glaze needs to precipitate =3D20
to the surface to create an iron red. To find out how much iron you =3D20
need in your glazes, create a line blend with 0% iron red at one end, =3D20=
=3D
and 20% iron red at the other. I do a 10 part blend so that the glazes =3D2=
0=3D
I get from it contain iron in amounts that increase by 2% from 0 up to =3D2=
0=3D
20. In my kilns with my firing schedules, I find that I get the best =3D20
iron reds in the 8-12% iron range, but your kiln might fire =3D20
differently than mine. Creating a line blend will help you dial in on =3D20=
=3D
how much iron you need in your iron red glazes.
Try different types of iron oxides
I have used Spanish iron oxide, refined red iron oxide, black iron =3D20
oxide, yellow iron oxide and some wet concrete colorants from Home =3D20
Depot and have achieved nice iron reds and Jen's Juicy Fruit glazes =3D20
with all of them. Some potters feel strongly that the type of iron you =3D2=
0=3D
use has a big influence on whether or not you get a nice iron red =3D20
glaze. I haven't found this to be the case in my kilns. I think using =3D2=
0=3D
line blends and finding the sweet spot in terms of the amount of iron =3D20=
=3D
in your glaze and working with different cooling cycles is more likely =3D2=
0=3D
to get you moving in the right direction. But if you are still =3D20
struggling and want to try something, you could try different types of =3D2=
0=3D
iron oxides.
Clay Body Choice is Important
Different clay bodies react differently to iron red glazes. I get good =3D2=
0=3D
results on Tuckers Mid-White clay body and on Rovin's RO-10 Stoneware =3D20=
=3D
body. Try the different clay bodies that you currently use before =3D20
switching to a new one. Do line blends and vary the cooling cycles. =3D20
These procedures might help you dial in on an iron red glaze and =3D20
firing process that will work in your kiln.
John Post
Sterling Heights, Michigan
http://www.johnpost.us
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