Richard Busch article - Wood fired look from elec kiln

[cp dunbar]

Great article from CM i believe by Richard Busch using 3 diff glazes to get wood fired look from elec kiln - examples are noteworthy

he uses a version of mixture of nutmeg, white satin matte glaze, and a dark "sybil's black stain"

all recipes listed in CM article and in CM Glazes: Materials Recipes and Techniques and other books also showing same.

will try to fire once firing schedule worked out and place pix here

cp by the pond / where some irritating plants are growing............ hmmm

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[George Lewter]

I use his Nutmeg extensively as a base and layer other glazes on top. Have had good luck spraying it on greenware, drying between coats. Have had bloating issues when I dipped it more than once on raw clay. Check in the network Search box for the many existing comments about Nutmeg glaze.

[Norm Stuart]

Using wood-fired glaze recipes, from John Anthony's Red Hill Pottery site, I discovered most of the glazes he uses are refractory at ^6 in an electric kiln - especially his Woo Yellow. I suspect this means wood-fired kilns are actually doing additional heat work after the correct Witness Cone has bent, because you can't simply turn-off the wood kiln.

http://www.redhillpottery.com/cone6oct03.html

Only the "Bailey Shino" looks the same in our electric kiln at ^6, with or without slow-cooling.

One glaze in particular, "Shocking Shino", I think looks strikingly better in an electric kiln - but shows pin-holing, I think signs that it could still use either more flux or more heat work. As with a gas kiln there may be other differences due to a partial reduction or the slow-cooling nature of hard fire-brick.

Shocking Shino ^6 in a wood kiln

Shocking Shino ^6 in an electric kiln.

[cp dunbar]

ok, so i tried the nutmeg glaze and i got a great deal of "creamy color" .  It appears that the glaze is too thick. Have you had this problem, and what hydrometer do you use ?

Also "Sybil's Black" from the same author, came out too runny, so it is now sitting with the top off to dry.

Is there a sort of range for sp grav that works well ?

[Norm Stuart]

I got the same "creamy color" result with Ron Roy's Nutmeg Revision, from Alisa Clausen, which also uses Yellow Ochre (3.24%) and Red Iron Oxide (1.07%).

http://www.flickr.com/photos/glazes/1084685267/

Rather than question the thickness, I wondered about the consistency of Yellow Ochre.  Digitalfire lists Yellow Ochre as having only 22.01% Red Iron oxide.

http://digitalfire.com/4sight/material/yellow_ochre_1714.html

I replaced both the Yellow Ochre and Red Iron Oxide with 3% Spanish Iron Oxide (87% Red Iron Oxide) to get a consistent result.

http://digitalfire.com/4sight/material/spanish_red_iron_oxide_2244....

Nutmeg with Yellow Ochre (creamy result in my kiln)

.

Nutmeg w/o Yellow Ochre or RIO, with 3% Spanish Iron Oxide

.

Nutmeg with Burnt Umber, 54% Iron Oxide, instead of Yellow Ochre

http://digitalfire.com/4sight/material/burnt_umber_151.html

[cp dunbar]

Hydrometers  - how do you measure specific gravity for glaze thickness uniformity ?

[Norm Stuart]

I weigh or measure out the water for the glaze in grams or mL. I'm not very potterish in that way. Most glazes get mixed one kilo of dry ingredients to one kilo of water. Only a few glazes are exceptions to this.

Our base glazes for mixing with colorants are required to remain in this ratio so we can measure out 200 mg of wet glaze, and know we are tinting 100 mg of dry glaze.

But as for the other finished glazes, we have people who want to make their glaze the consistency of cream, or others like to use a hydrometer to measure to a certain specific gravity. I let them do as they prefer.

When I see a glaze recipe with 6% or 8% bentonite and too much colorant oxide to develop the color they're looking for, I understand the glaze creator was trying to apply the glaze thin. So I reconfigure the glaze ingredients look the same using a maximum of 2% bentonite. I've never found a glaze recipe which specified a certain finished density when mixed with water. It's all subjective.

I've read comments online where people refer to a "thick Chun" or a watery glaze - none of that means much to me.  When studio members see my test tile on the glaze lid they can say, "oh that's too thick I'll thin mine", or "gosh I'll have to let that evaporate in the sun or it will never stick to my previously fired piece".

I have more background in chemistry than I do with ceramics, so I've never had much patience for a glaze that is difficult to fire correctly. I believe a glaze like that needs to be reformulated so it fires consistently.

Two years ago, before I started making glazes, folks at our studio used prepared glazes. One Amaco glaze in particular "Ancient Jasper" (which is called "Floating Red" on Digitalfire) never fired the way the manufacturer showed on their website. The chemist who made the glaze was on the customer website telling people to find a cooler or hotter corner of their kiln to make it come out better, or to paint on various thickness of his glaze. That's ridiculous. Floating Red made with red iron oxide precipitate is identical to the Amaco Ancient Jasper.

This is how Amaco says "Ancient Jasper" can look if only you fire it correctly. No commercial ceramic maker would tolerate a Will-o-the-Wisp glaze. An unreliable glaze is not my idea of art.

This is a tile of Floating Red over Amaco "Firebrick Red". It's indistinguishable from "Ancient Jasper" over "Firebrick Red".

[Norm Stuart]

Another thing to bear in mind when using an iron oxide glaze, is that white clays will bind a significant amount of the iron oxide out of the glaze melt.

So Nutmeg glaze on white clay is far more likely to end up looking creamy, while Nutmeg glaze on brown clay is far more likely to be more colored by the iron in the glaze.

These are several examples of Orange Street glaze which uses 12% Red Iron Oxide Precipitate.

The first two are slow-cooled at 10 degrees C between 982 and 815 C.

Orange Street glaze on white clay on the left is matte, while on the right Orange Street is glossy on brown clay.

This example is Orange Street on a white clay tile was slow-cooled much faster at 85 degrees C per hour between 982 and 815 C.  It looks similar, but different.

[Jonni Webb]

cp dunbar said:

ok, so i tried the nutmeg glaze and i got a great deal of "creamy color" .  It appears that the glaze is too thick. Have you had this problem, and what hydrometer do you use ?

Also "Sybil's Black" from the same author, came out too runny, so it is now sitting with the top off to dry.

Is there a sort of range for sp grav that works well ?

[Jonni Webb]

Jonni Webb said:

CP, I made the nutmeg and white glazes from that article, too... LOVE the white satin matte glaze. Need to remake it, actually...I use it a lot. The nutmeg never did look anything like the pictures. Mine was way too creamy looking too...have used some but never really happy with it...

cp dunbar said:

ok, so i tried the nutmeg glaze and i got a great deal of "creamy color" .  It appears that the glaze is too thick. Have you had this problem, and what hydrometer do you use ?

Also "Sybil's Black" from the same author, came out too runny, so it is now sitting with the top off to dry.

Is there a sort of range for sp grav that works well ?

[George Lewter]

Floating Red has worked occasionally for me as in:

•  as a base with drizzles of Waxy White.

• Or here layered on top of Waxwing Brown.

I've not used it much lately because it was not consistent, and it is way outside limit formulas for a durable, stable glaze.

[Norm Stuart]

Wow! Especially that tray. That's the sort of thing we might have hoped for. Your Floating Red over MC6G Waxwing is close to what we expected but never achieved.

We gave up on trying to achieve an "Ancient Jasper" look using one glaze a long time ago.  But I was glad to compare it with "Floating Red" in Digitalfire using synthetic red iron oxide and discover it is an identical recipe. You're right it isn't a stable glaze recipe, and the surface is sometimes very abradable.

I've come to greatly value glazes with reliably repeatable results.

This is how "Floating Red" over Amaco's "Firebrick Red" supposedly turns out -  I even asked Steve Lampron at Amaco (VP Technical Services) for advice by email. All he could say was vary the thickness of the glaze and try hotter or cooler. Didn't work for us.

http://www.amaco.com/steve-lampron/