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Iron Red Cone 5

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I'd like an opinion on these iron red oxidation glazes as far as durability and general formulation. I don't typically use anything that has this much Gerstley Borate. I got this off of a blog or forum, not sure where so I can't give credit. The one at the bottom is done as a batch, but only has about 26% gerstley borate, but 45% gerstley borate seems extreme to me.




JO'S RED ^5-6 O


Gerstley Borate45


EPK 10


Talc 15


Flint 30




Use THICK for good red





EPKaolin 5

Silica 30

Cust .Felds 20

GBorate 32

Fe2O3 15






EPK 5.88

SILICA 29.41


TALC 13.73


add RED IRON OXIDE 14.71





Iron Red Glossy Cone 5,OxidationPotash Feldspar - 1000

Gerstley Borate - 1500

Talc - 750

EPK - 250

Silica - 1500

Red Iron Oxide – 750



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I had my first successful firing yesterday Hooray! <br style="font-family: arial, sans-serif; ">I was having load of problems with getting up to the right heat, but

now all is well in mudville, except, my greens are red, my tans are

blue, my lavenders are tan.


I am using a natural gas kiln, top loading.


The glazes are premixed in powder form, Moroccan sands from Laguna. I

have used the same colors before, but they were fired with an electric

kiln, by my instructor. Now, I am on my own, and I know I have a lot

to figure out.


What it looks like to me, is some reduction's going on. The colors

turned out not unlike cone 10 glazes I have seen. They are quite

lovely, but not what I was after.


I know I got to temp, and maybe a touch hotter, as the cone 6 in my 4

5 6 cone pack slightly melted, and my self supporting cone 5 cone

completely melted. Since the kiln is new to me, I have put many items

of heat measurements in place, just to get to know the kiln.


I have also fired most of the ware a few times, while I was not

reaching proper temp. I don't believe that would have made a

difference, but perhaps it did?


Anyway, if anyone has some words of wisdom, I would love to hear them.




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You'll get more response by posting a new thread instead of a reply to this tread.


Yes it sounds like you had significant reduction going on in your kiln. You can talk to a Laguna representative about the best atmosphere, they might be able to guide you in firing their glazes better than me because I don't use them. If you have the ability to open up your secondary air that could help you oxidize, as well as opening the damper slightly. Obviously you'll want to hit peak temperature and soak, but then instead of turning off the gas you can try firing down in oxidation by giving the same fuel more air. This can burn off some carbon and brighten your colors. I know a guy with a downdraft that cracks the door of his kiln and fires down in oxidation to brighten his iron reds. Not suggesting you do this unless you're comfortable with your kiln as it could be somewhat dangerous.

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