Yellows
HELLO YELLOW
GLAZE OF THE WEEK 14
WHAT MAKES YELLOW?
HPG HAS SEVERAL YELLOW CHOICES v UNSTABLE VS STABLE YELLOWS
USED AS BACKGROUND FOR DESIGNS
Uranium makes yellow. Ever heard of “Yellow Cake” the stuff used to make atom bombs? Vanadium, Cadmium, Nickel, Manganese and Lead also make yellow. These minerals have been used to make yellow in paint and glaze, not at HPG.
Forget these dangerous heavy metals and radioactivity. Let’s just use what is safe.
What about good old Iron which in different states can change color from yellow to brown to black? The colors of Iron can be manipulated by the amount with other chemicals mixed with it. Red Iron Oxide at about 2% with Rutile , which is Titanium plus some iron, gives a good yellow glaze. . Magnesium is also used to get yellows with salts of Zirconium. HPG has a variety of glazes which are yellow depending upon the firing , thickness and the clay body. Dark clay bodies will come through with brown flecks or patches.
1. STONEWEAR YELLOW is the forgotten but most reliable yellow glaze at HPG, a classic. On iron rich clay it is a good soft yellow with some brown markings picked up from the iron in the clay. It has a satin matte finish. The firing is best in reduction at cone 10. Where thick it is yellow, brown where thin. A simple design using cobalt or iron oxide with stonewear yellow works well as an accent if desired. On porcelain it doesn’t do very much: just a chalky yellowish color without much character. There are currently two buckets of stonewear yellow at HPG. #1 is the typical yellow as it is meant to be. #2 is much less yellow, and more beige with brown. For as long as it lasts, it is very good looking. Both are very stable.
2. TOSHIKO ORANGE is the popular golden yellow accent often used with good results on Tenmoku. It is not stable and will run like mad off the pot if too much is used pushing another glaze off with it. It is a cone 9 glaze. Brian Molmen prefers to use a trail of it for interest under a cone ten glaze like Tenmoku or Ohata. Both of these glazes tend to keep the Toshiko Orange more stable because they melt at a higher temperature.. Used on Miller White or clear glazes is disappointing because it comes out very egg yoke yellow. The result of using it with a metallic glaze high in Iron is a shimmery golden yellow design. Sometimes, if the conditions are just right, it can have a golden patina.
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3. EGGSHELL is just like its name, a smooth satin matte glaze, off white to light cream in color. It is very stable. It is also sensitive, picking up a slight tinge from a neighbor in the kiln. If this happens it can be very interesting with a blush of lavender pink from copper. If you want a soft, “baby skin” feel to a glaze, this could be it. Another Eggshell, #2, is more like a brown egg, tannish in color. Eggshell White is just that: very white.
4. ACERO is new cone 10 glaze introduced by Yoko Haar, which has become quite often used on carved, dark clay bodies such as Letty’s tall carvings for the best effects. It is yellow where thick, and a rich rust-brown where it is thinner. It doesnot run at all.
5. MAJOLICA is the cream-colored, semi glossy cone 10 glaze, which has been used for ages as a good background for colored designs in Spanish and Italian ware. It is stable, and covers fairly well, but on dark clay some brown flecks will come through. Colored oxides and overglazes work well with Majolica.
6. YELLOW STAINS, quite a variety of them, are available. They contain elements like Vanadium, Barium and Zirconium to make them work, so using them carefully would be important. Most yellow stains lose color in cone 10 reduction firings, but can last through oxidation firings. Ceramic stains are usually mixed into a white clay slip, then used as an underglaze. A clear glaze like Chun or Nelson’s Transparent when put over it can minimize the yellow color, or any other glaze with tin or zinc in it. If the yellow stain is “encapsulated” in a new process, the yellow color is much stronger and lasting. For painting designs on a white clay body, AMACO Velvet “Intense Yellow” is very good in either oxidation or reduction conditions.
7. MAMO is thought of as a white glaze, but when applied evenly in a thin coat on dark, iron rich clay, the blackground is yellow with the usual iron freckles showing through. Queenie Kwock uses this glaze very effectively.
8. “F” Glaze is very bright Dijon mustard yellow on white clay; and bright yellow on dark clays. Steve Martin has made beautiful things with it. It is a matte glaze. The yellow comes only from a form of iron which is produced during firing with other components of the glaze.
9. “Yellow Ash”, an iron yellow glaze is being tested.
Pat Harwood 11/01/06 ed Jan 2007 4/15/07 Jan 2009, April 23, 2009 Nov 2010.
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