Potters & Sculptors - Making Rock from Mud
These are the glazes that Steven introduced us to for creating the layered effects for which he is renown. This is the place to post modifications for these glazes, and other glazes that you have found to work well with SCM and SCM for orange.
2-D blue sprayed very thinly over the other layered glazes can produce a "snowflake effect.
And following are companion glazes that Steven has used on his pots.
Lawence, you are correct that the images are a from a Filemaker application. The software application is Glazemaster by John Hesselberth at http://www.masteringglazes.com/glazemaster/. He is also the author of the book Mastering Cone 6 Glazes
Glazemaster is available for download as a free 60 day trial, and the full license is only $40, which is a far better expenditure than the work you will do trying to duplicate it.
Issues with Hannah's Fake Ash Blue and SH Green Ash.
My pots with HFA Blue have been developing mostly greenish brown surfaces with blue occurring only where mixed with other glazes, where previously the glaze had come out 50% or more in blue coloration and with strong development of legs and rivulets in the areas with the isolated glaze (not layered with other glazes).
With the SH Green ash where I had hoped for purer green rivulets, I am seeing minimal movement into rivulets, and the predominate color is a gun metal greenish gray.
Is anyone else experiencing similar outcomes or overcome similar issues.
The path to making cobalt green requires a high-alumina glaze in combination with a little titanium (rutile), especially if fired hotter than Cone 6. If you have created a new path to cobalt green, you've inadvertently discovered something wonderful.
You're also dealing with two other problems - Strontium Carbonate and Lithium Carbonate.
I've recently learned, from John Baymore, that barium and strontium carbonates do not always reduce to oxide. In many firing conditions it remains as little particles of strontium carbonate mixed with the glass - therefore not acting as a flux. This can result in barium carbonate and the strontium carbonate glazes you're using being unreliable in flow.
Another problem is many Barium carbonate recipes have been "reformulated" with the same gram weight of Strontium Carbonate, when they should use 75% of the original weight of Barium Carbonate. Using a 1 to 1 ratio instead of a 1 to 0.75 ratio for replacement can obviously change the glaze color and properties. We also don't really know if strontium is safer than barium - Laguna Clay lists them as equally hazardous.
I've also found Lithium Carbonate far less than reliable when not milled finely enough. When you look at even finely-milled Lithium Carbonate the mesh-size variation is still all over the place.
Even though it costs three times as much, I've found Lithium Fluoride to be a very reliable replacement for Lithium Carbonate, whether due to the mesh-size or the permanently-attached fluorine, I don't know. But Jen's Juicy Fruit was really annoying in it's unpredictability until I replaced our very granular lithium carbonate with the fine powdered lithium fluoride.
If this were not you posting this, I would also mention that many at our studio are generally unhappy with "ash overglazes" because they don't test them with their glaze on a test-tile. So they're often adversely surprised by the interaction between the two glazes when they mix.
Using 2012 updated recipes for SH Red Orange and Jen's Juicy Fruit w/ red iron oxide, I made single fire tests on Laguna B-Mix 5. Tested them in a gas kiln firing to cone 7 with mild reduction and a one hour hold on cooling (oxidising) at 1675 F.
The "crocus martis" for the Red Orange was from Arizona Clay Company and is supposedly Bayferrox 180.
On the left is the SH Red Orange, center is Jen's Juicy Fruit, right is Orange Red over Jen's Juicy Fruit (one dip each color)
Planning to repeat this test in my electric kiln for comparison.
Strontium carbonate is much less toxic than many other ceramic materials. People often confuse it with radioactive strontium 90 from nuclear weapons.
Below is an extract from a materials data safety sheet for strontium carbonate:
V. HEALTH HAZARD INFORMATION
Effects of Exposure:
To the best of our knowledge the chemical, physical and toxicological properties of strontium carbonate have not been thoroughly investigated and reported.
Strontium compounds have a low order of toxicity. It is chemically and biologically similar to calcium. Strontium salicylate is the most toxic compound. The oxides and hydroxides are moderately caustic materials. (Sax, Dangerous Properties of Industrial Materials, eighth edition)
Inhalation: May cause irritation to the respiratory system, coughing and shortness of breath.
Ingestion: May cause excessive salivation, vomiting, colic and diarrhea.
Skin: May cause irritation.
Eye: May cause irritation and visual impairment.
Inhalation: May cause pulmonary edema.
Ingestion: No chronic health effects recorded.
Skin: May cause dermatitis.
Eye: No chronic health effects recorded.
Routes of Entry: Inhalation, skin, eyes, ingestion.
Medical Conditions Generally Aggravated by Exposure: Pre-existing respiratory disorders.
Carcinogenicity: NTP: No IARC: No OSHA: No
Issues of food safety are extensively discussed elsewhere on this network (try the search box at the upper right of our full web page). The general convention for production potters is to use a completely non-toxic clear or white liner glaze on the food contact areas of functional ware, or to have stock, colored glazes that have had sample pieces leach tested by a qualified laboratory.
15) Cornell Iron Saturate **
Yellow Iron Oxide
Use only as a second glaze for effect over a light glaze (egg shell, white SCM)
Cornell Iron saturate glaze has nothing dangerous to leach. It is a glaze you could use as a liner with more visual interest than clear or white. I often use C Harris Temmoku (another iron red) as my liner glaze.
Has anyone tried adding large amounts of iron oxide into jens juicy fruit? I am talking like 15-19 synthetic RIO? I am kind of curious what it would do. I am going to mix up a batch and fire it this weekend.
I am hoping that I can get a nice black with silver highlights from the concentration of RIO.
After trying different variations of Jen's Juicy Fruit, I concluded it was a glaze / over-glaze which needed to be used at higher temperatures than Cone 6.
At Cone 6 Jen's Juicy Fruit is more of an ugly brown engobe. Altering the recipe by adding more flux merely made it into an uninteresting brown glaze.
Like Weathered Bronze Green, Jen's Juicy Fruit began life as a Cone 10 recipe which should be suspect right off.