Geology and Ceramic Oxides

quartz

a mineral composed of silicon dioxide

flint

a sedimentary rock made up of microcrystalline quartz

silica

chemical compound silicon dioxide

two most common minerals in the earth’s crust

silicon and oxygen

Silicates

minerals that consists primarily of silicon and oxygen atoms. Basic materials of the earth’s crust and mantle. Form when molten magma cools. Building Block: Silica tetrahedron

oxides

minerals that consist of metal cations bonded to oxygen atoms.

carbonates

minerals that consist of metal cations bonded to the carbonate anion- like Whiting.

Three types of rocks

igneous, metamorphic, and sedimentary

igneous rock

formed from volcanic activity

sedimentary rocks

Formed from the erosion and weathering of igneous rocks.

metamorphic rocks

happen when other rocks are subjected to a ton of pressure or heat and turn into other things.

What kind of rock is clay

sedimentary rocks that are erroded away from feldspars.

Intrusive rocks (plutonic)

igneous rocks formed way under the earth’s surface (cools slowly, large crystals and coarse textures-granite)

Extrusive rocks (volcanic)

igneous rocks that come out during volcanic eruptions. (cools quickly- smaller crystals and finer grained textures- basalt, obsidian, pumice.

Bowen’s Reaction Series

Shows us the order in which different minerals form when magma cools. Isolated silicate structures, then chain silicate structures (pyroxene and amphibole), then sheet silicate structures (mica, illite clay), then framework silicate structures (quartz, feldspar).

Kaolinite Structure

sheets of silica tetrahedra bond with hydroxide to alumina octahedra to form platlets.

New Zealand Halloysite

In Kaolinite family, tubular crystal structure.

Bentonite molecular structure

sheets of silica and alumina, each sheet is silica alumina silica. Water can get in between each of the layers and expand the material.

hydrothermal alteration

action of groundwater containing weak solutions of deeply buried formations of chemicals, which have been heated through igneous activity, will have an affect on surrounding rocks (usually deep underground or near hot spring activity).

Raw materials from igneous processes

soda feldspar, potassium feldspar, nepheline syenite, spodumene, quartz, chromium, and iron.

sedimentation

weathering from the mechanical actions of water. Weathering, erosion, transportation, deposition, and lithification.

raw materials from sedimentary processes

Calcite, flint, dolomite, strontium, gypsum, phosphorite, kyanite, kaolinite, and shale (clay).

Primary clays in terms of the rock cycle

Don’t move much from where they are formed.

Secondary clays

Are transported through weathering and erosion- also called sedimentary clays.

Regional metamophism

affects a large area undergoing large increases of temperature, stress, and pressure. (occurs at convergent plate boundaries)

Contact Metamorphism

near molten magma or lava, high temperature and low pressure.

raw materials from metamorphic processes

talc, mica, slate, wollastonite, orthoquartzite, marble, zinc, talc, molybdenite.

Organization of the Periodic table for ceramics

First column is primary fluxes (lithium, sodium, and potassium), secondary fluxes (Magnesium, calcium, strontium, barium), Then colorants and opacifers (modifiers), then rare earth elements on the bottom, glass formers in the upper right hand corner.

Name the primary fluxes/ alkaline metals?

lithium, sodium, potassium

What are primary fluxes?

Alkali metals that are extremely reactive, powerful fluxes. Found naturally in combination with other elements. Na and K act alike, KNaO. Fluxing power decreases as you go down the group.

What are properties of high alkali glazes?

Glassy, glossy, fluid, clear glazes. High expansion and contraction (tend to craze or shiver). Li crazes less than Na or K. They make the most intense, bright colors and tend to singe the clay body orange-red. Sodium and potassium counteract settling /flocculating glaze slurries and can be used as suspension agents.

Sources of sodium (Na)

Nepheline syenite, minspar or F4 soda feldspar, pegmatite, soda ash, ferro frits like 3110, 3819, and 5301, and cryolite.

sodium oxide

Was one of the earliest melters used in ancient Egypt in faience (Egyptian paste). Stronger and more reactive melter, compared to potassium. Produces a more fluid melt even though its individual melting point is higher. High soda glazes will sometimes singe a clay body orange-red. Soda feldspars will turn pink in the presensce of copper vapor in a kiln more readily than other feldspars. Produces a greyer celadon when used with iron in reduction. Has high thermal expansion rate (causes crazing). Can cause bubbling in glazes due to volatility above 2327 degrees farenheit. Salt is used on its own to create the orange-peel salt glaze.

Examples of sodium in shop glazes

shino, shiny black, selsor temmoku, and philly green.

sources of potassium?

potassium feldspars (custer, G200, K200, orthoclase), Pearl ash, and wood ash.

Potassium Oxide properties in glazes and clay?

Melts slightly slower than sodium, wider firing range that increases its use at higher temperatures. Causes a slower and more viscous flow in glaze melts. Creates a slightly more stable and stronger surface because it dissolves silica more effectively than soda. High thermal expansion rate. Produces pure blues in iron-based celadons.

Shop glazes with potassium?

White liner, shiny black, shino, and temple orange.

Sources of lithium?

spodumene, lepidolite, lithium carbonates, amblygonite, and lepidolite.

Lithium properties in glazes and clays?

Lithium is found combined with other elements- the purest form is lithium carbonate. Superior fusin, hardness, and thermal properties to sodium and potassium. Increases the fluidity and gloss of a glaze (can help pinholes). Melts at higher temperatures than sodium and potassium but forms a more fluid melt. singes clay bodies yellow-orange. Turns celadons greener and yellower. Produces bright colors. Lower thermal expansion rate- can cause shivering if used too much but can also heal crazing.

Shop glazes with lithium?

Shino, van Gilder red, butterscotch, spodumene, and philly green.

What do we use most often to get our primary fluxes in glazes?

feldspars

Feldspar

Minerals with a mixture of aluminium silicates of sodium, potassium, or lithium (Mainly or some calcium).

Feldspar properties in glazes and clays

Usually have around 10-15 % KNaO. Used in clay bodies to promote vitrification by forming a glassy phase that cements refractory particles together and causes mullite to form from clays. In glazes, used as a source of insoluble alkali fluxes, silica, and allumina. Feldspar can be glazes by themselves but don’t have high thermal expansion, causing crazing in the finished piece. Feldspar-heavy glazes also settle in the glaze bucket because of the lack of clay in the recipe.

Examples of feldspars?

Nepheline syenite, minspar, G200 Feldspar, Mahavir Feldspar, Custer feldspar, spodumene, and cornwall stone.

Name the secondary fluxes/alkaline earth metals?

Magnesium, calcium, strontium, barium, and zinc oxide.

Secondary fluxes properties

Oxide forms are RO one to one with oxygen. Less soluable in water than primary fluxes, less bright color response. Act in eutectic mixtures to lower melting point of the glaze. Stabilize the glaze and make it more durable.

Calcium Oxide (CaO) properties in clay and glazes?

Hardens a glaze, resists acids in foods, and has a modest expansion and contraction rate. calcium + kaolin + flint+ the first high fired glaze developed in China after straight wood ash. When calcium is less than 25% of a glaze’s materials, it acts as an active melter. In higher amounts, it may cease to act as a melter, instead forming calcium silicate crystals, which create a waxy, satin, opaque surface. Above 40% calcium dries and matts the glaze. Calcium is the most important auxiliary melter in stoneware glazes- it dominates in many Song Dynasty celedon glazes. A glaze with pure calcium provides beautiful blue-green celadon colors.

Sources of calcium?

calcite, dolomite, wollastonite, colemanite, anorthite, wood ash, bone ash, and fluorspar.

Shop glazes with calcium?

Mouse black, celadon, clear blue, bates clear, and copper red green.

Magnesium oxide properties in glazes and clays?

Magnesium can produce silky smooth, buttery mattes at the stoneware range. Low thermal expansion rate, useful to fight crazing. In low fire glazes it can act as a refractory and cloud up a glaze or make a sugary matte. Magnesium is usually used in combination with other fluxes. Good flux above 2138 degrees farenfeit. Tends to produce pastel shades of color. In large amounts causes crawling and beading due to increasing the surface tension of the glaze melt.

Sources of magnesium

talc, dolomite, magnesium carbonate, and magnesium oxide.

Shop glazes with magnesium?

Pike’s purple, van gilder red, spodumene, soft blue, butterscotch.

Barium (BaO) properties in glazes and clays

Poisonous in its raw state, unless used fired into a frit. Barium can leach into food in glazes that are not formulated properly. Barium is a strong flux that can produce silky matte glazes that also may be runny. With boron in the glaze, barium will remain glossy. High amounts make dry smooth mattes. Barium glazes have brilliant color response to solorants. Good flux above 2147 degrees farenheit. NOT FOOD SAFE!

Sources of barium

barium carbonate and some frits like 3289. Strontium is a good replacement, multiply barium by .75.

Strontium Oxide (SrO) properties in glazes and clays?

Strontium is used to replace barium in glaze recipes (75% of strontium per amount of barium). Effects are somewhere between barium and calcium. Good for mid-range and high fire stoneware temperatures. Similar expansion and fluxing power to calcium oxide. Interaction power is more like zinc- can help precipitate a crystalline matte surface. Develops vivid colors. Good flux above 1994 degrees farenheit.

Sources of strontium

strontium carbonate

Strontium in shop glazes?

philly green

Zinc (Zn) properties in clays and glazes?

Acts as an auxiliary flux, opacifier, and crystalizing agent. Affects the melting process, making glazes melt easier. Makes glazes more durable and can reduce crazing. Usually dulls down colors, especially copper, iron, and chrome but can help blues, browns, greens, and pinks (thus the zinc- free clear). Glazes with zinc have high surface tension and are prone to crawling (they shrink more in the early stages of firing, causing cracks that develop into crawled areas- can be calcined to combat this.)

Zinc oxide in shop glazes?

Temple orange and pike’s purple

What are frits?

human-created raw material blends with specific
formulas that are sintered together by firing and then
ground into a powder

Properties of frits in clay and glaze recipes

Commonly used to render soluble materials insoluble, or toxic ingredients safer to work with. Oxides in frits are more refined, producing results with fewer defects, better clarity, smooth surfaces, brighter colors, and a nice melt (don’t gas off in the firing). Used to achieve oxide blends that are complex and difficult with straight raw materials.

Name the modifiers

Titanium, vanadium, chromium, magnesium, Iron, cobalt, nickel, copper, and zinc.

What are modifiers?

the most common colorants

Titanium dioxide properties in clays and glazes?

Rutile is an impure titanium, with some iron. Rutile and titanium can produce yellows, tans, and browns. Can provide variegated surface and can induce crystal growth. In salt or soda firing, the sodium brings the titanium to the surface of the clay and results in flashing.

Vanadium Pentoxide properties in clays and glazes?

Provides strong yellows. Produces variegated effects and textured glazes. Extremely toxic and bad for the environment. So we try not to use it often except in the fritted form.

Chromium oxide properties in glazes?

Can be a deep grassy green or at other times, a bright chartreuse. Chrome can also produce yellows, pinks, and browns in various glazes Chrome is refractory and may
matte or opacify a glaze. Chrome fumes in the kiln, sometimes blushing onto nearby
glazes. With tin, used to create chrome-tin pink glazes.

Manganese dioxide properties in glazes?

Produces purples and browns in glazes. High percentages produce metallic surfaces. Can be used as a wash or to stain a clay body. Extremely toxic when it builds up in your system

Properties of iron oxide in glazes?

Iron is the most pervasive material on the earth and the most common colorant in ceramics. Flashing in salt firing and reduction firing is caused by the interaction between iron and
titanium and sodium. There are yellow (Fe3O 4), black (FeO), red (Fe2O 3), and many
shades of brown iron oxides. Iron is a flux as well as a colorant

Properties of cobalt carbonate in glazes?

Cobalt Carbonate – CoCO 3 is the best source with good color response. Cobalt Oxide -- CoO. Cobalt is very blue. Cobalt is a flux and blue.

Nickel Carbonate properties in glazes?

Ususally we use NiCO 3 but also: Green Nickel Oxide - NiO. Black Nickel Oxide – Ni2 O 3. Can create a huge range of colors in glazes, from green, grey and blue to purple and
yellow. Nickel encourages crystallization. Nickel is refractory

Properties of copper carbonate in glazes?

Forms of Copper: Copper Carbonate – CuCO 3 -offers the best color response. Black Copper Oxide – CuO –coarse, soluble. Red Copper Oxide – Cu2 O. Produces greens, blues, copper reds. Copper is a strong flux. Copper can volatize (burn away) in the kiln

Uranium history

We don’t use uranium any more because its radioactive.

What is an encapsulated stain?

encasing a toxic material and encapsulating it in material to keep it from being toxic. Really good for reds, yellows, and oranges at cone 6. Look at mason stain reference chart when formulating your glaze recipe.