Feldspars

• the most common mineral on earth
• decomposed granite
• act as fluxes

• feldspar-like
• works at lower temperature
• has more sodium
• flux

• feldspar-like
• a source of lithium
• has low thermal expansion
• flux

• feldpsar-like
• contains calcium, potassium, fluorspar
• flux

• a source for magnesium
• a low temperature flux

• act as fluxes
• are calcined combinations of minerals

• boron + calcium
• a powerful flux

• the essential glass former
• binds clay particles
• gives strength to the clay body

• silica particles expand upon heating and contract upon cooling

• a pre-fired and ground particle added to clay to give tooth and strength
• also acts as clay opener 
• helps lower temperature shock
• helps clays dry more evenly, and with less warping

• silica sand
• molochite
• pearlite
• combustle organic materials

• the tooth helps with strength 
• an open clay body helps the pot survive the thermal shock of the Raku firing process

• a flux
• calcium silicate
• helps lower clay shrinkage
• good for sculpture bodies

• bonds with excess calcium salts to prevent scumming in clay
• used in terra cotta 

• increases plasticity in clay
• suspends particles in glaze
• swells in clay bodies
• extremely small particle size

• increases plasticity in clay
• twice as plastic than bentonite 
• used in white clay bodies because bentonite adds colour

• strengthens raw clay
• reduces shrinkage
• nylon fibers can survive firing as glass network of threads - fired strength
• paper clay can make working with thin clay easier

pyrophillite

• non plastic aluminum silicate
• reduces clay shrinkage
• used in flame- or ove-ware bodies
• extends a clay's firing range
• preshunk, prefired - filler
• fire to high temps

• slip is the general term for any clay in liquid form
• it can be used to apply on the surface of wet leather-hard clay or for slip-casting
• engobe is the specific term for liquid clay applied to leather-hard clay or bisqued clay
• they can all be coloured with metal oxides or stains

• an ultrarefined clay slip that can give a soft sheen when applied to bone-dry wares and, if polished or burnished while still damp, may give a high gloss.
• is made by mixing a suitable clay with water and a deflocculant and leaving it to stand until the heavier particles of clay settle out. (Deflocculant weakens the electrical attraction between particles of clay, thus breaking up small clumps of clay and allowing the individual particles to float freely.) The deflocculant causes the finer particles to float in the water, which can then be decanted for use. 

• food safety
• water-tight sealing
• to make surfaces sanitary
• durabality
• layer of strength on the surface
• aesthetics

• temperature range, incredients (ash, bristol, etc)
• by character (shiny, satin, matte, etc)
• by light transmission (transparent, translucent, opaque, etc)
• durability
• texture

• silica
• calcium

what are the causes of glaze crazing?

what are the solutions?

What are the causes of glaze shivering?

what are the solutions?

what are the three basic categories of glaze materials?

name an example for each one

• glass former: silica
• refractory: alumina
• flux: neph sy

• sodium
• potassium 
• boron

• runny and weak with not enough alumina
• dry with too much alumina

what happens when there is too much alumina in a glaze?

what happens when there is too little?

• too much: causes a glaze to stiffen and tend towards opacity, again with a textured surface where it is dry in spots.  Glazes will often have pinhole defects.  Too much alumina can inhibit the melting of the glaze to the extent that a poor quality matt glaze results, one that looks matt but is prone to discoloration.
• too little: causes the glaze to be runny

• a source of alumina and silica
• primary clay
• helps suspend glazes
• gives raw glaze surfaces greater strength

What is calcined kaolin?

• pre-fired kaolined
• it won't shrink

• has finer particles than kaolin
• secondary clay
• high shrinkage  

• secondary clays
• high shrinkage
• often will flux into glazes at high temperatures

feldspars 

name 4

• can provide the basis for glaze
• contain silica, alumina, and flux materials
• secondary fluxes for low fire 
• custer feldspar - potash
• minspar - soda (custer melts at a higher temp)
• neph sy, melts lower than soda spars
• cornwall stone - highest melting feldspathic due to calcium

• a source for calcium 
• high temp flux

• a matte stoneware flux
• high shrinkage
• can make crackle/crawl glazes

• a matte stoneware flux
• contains calcium and magnesium 

• a lithium spar
• low expansion

• a very active flux

• calcium and phosphate
• a flux
• gasses when it melts

• toxic
• strong matte flux 
• brilliant colour effects
• substitute strontium carbonate

• active flux in small amounts
• if there's too much it can bubble, opacify, crater
• essential in crystalline glazes

• source of boron 
• strong low temp flux

frits

what are they and why do we use them?

• frits are calcined glass
• they cut down on solubility 

why use bentonite in a glaze?

• as suspender so the materials settle less

• it acts as a suspender

• The term 'limit formula' historically has typically referred to efforts to establish absolute ranges for mixtures of oxides that melt well at an intended temperature and are not in sufficient excess to cause defects. 
• These formulas typically show ranges for each oxide commonly used in a specific glaze type. 
• limit formulas are good to use as a starting point in fiding a glaze recipe that works but they are not absolute

zinc oxide is necessary to form crystals in a crystalline glaze

no refractory material

• seperates glaze materials into 3 categories: fluxes, glass formers, and refractories
• all fluxing oxides add to 1, which is the "unity" in the formula
• shows the ratios (in terms of relative number of molecules) of flux to alumina, flux to silica, silica to alumina

explain "atomic weight"

explain "molecular weight"

• atomic weight is the weight of the elements (their subnumber taken from the periodic table)
• molecular wieght is the combined weight of the elements in a formula

• iron oxide
• cobalt carbonate
• copper carbonate
• manganese dioxide
• manganese carbonate

• superpax/zircopax
• tin oxide
• chrome oxide
• rutile

• mason stains are commercially produced colourants for all temperatures
• they can be used to colour glazes or use as washes

• underglaze: can be put on greenware
• overglaze: china paints, enamels, (done last, low-fire)
• on-glaze: decoration on top of raw glaze ie majolica

• the sitter cone is specially formulater for the weight of the sitter to help it bend at a specific temperature
• the visual cone is a more accurate work + temperature reading 

• water is driven off
• organics are burned off
• clay achieves partial fusion
• is left porous enough to put glaze on

yellow/orange: reduction

blue: oxidation

green: neutral

oxidation: not restricting oxygen

reduction: carbon replaces the oxygen in the ware and causes colour change in the clay and the glaze

• using a sagger
• adding silicon carbide

• kiln wash is usually a mixture of alumina hydrate and kaolin
• it is used to coat the shelves so that if the glaze runs it will not ruin the shelves

• lithium(rarely used by itself, helps increase melt at any temp: higher the temp, the less you need)
• boron/gerstely borate/borax(major earthenware flux)
• zinc oxide (at low percentages)(low stoneware temps)

• any range
• primary fluxes in stoneware glazes
• secondary fluxes in earthenware glazes

• swap potash for feldspar
• swap sodium spar for NEPH SY
• add gerstely borate in 5% increments
• add frit 3124 in 10%-30% increments
• add frit 3134
• add 20%-30% of frit 3185/3269
• add barium frit 10-20%
• add lithium carb in 5% increments
• decrease clay amount

• primary fluxes: 
• potassium/sodium feldspars
• gerstely borate/boron frits/borax
• calcium oxide/whiting
• secondary fluxes:
• lead
• magnesium/dolomite/talc
• zinc oxide(in small amounts)

• common because it has trace materials in glaze
• black oxide: reduced form of iron oxide
• red iron oxide
• spanish red iron oxide: more consistent
• occurs in most earthy substances
• active flux in most temps especially in high fire reduction
• melts at 2600 degrees on its own

• metallic element 
• strongest colourant
• use .5% - 4%
• 4% = dry black
• fluxing colourant
• stable at all temps

• metallic element
• fluxing
• melts by itself at 2000 degrees
• makes greens, turquoise green

• zirconium oxide/dioxide
• opacifier
• white or bluish white
• subsitute for tin which is more expensive
• harder, shinier than tin
• combines better with other colours than tin
• refractory - melts at high temps
• low thermal expansion
• less crazing
• increases viscosity of glaze - less running

Tin oxide

• white, warmer than zircopax
• use less than zircopax
• more expensive
• helps develop red colours in reduction

• metallic element
• most versatile
• strong - use smaller amounts like cobalt
• green is flat, dense colour
• use 1-2% chrome for green, no more than 5%
• refractory: melts at 4200 degrees
• volatile colourant especially above ∆6
• toxic and carcinogenic - wear gloves and masks

• impure, natural form of titanium dioxide
• small amounts of iron and vanadium
• produces tan colour
• visual mottling/streaking
• visual runniness
• matte in high percentages
• opacifier
• microcrystalline formations
• blue colours in reduction

• brown to purplish
• use 2-10%
• more than 10% = iridescent/metallic
• can dissolve in some glazes
• toxic- use gloves
• fluxes at 1090 degrees celsius
• can cause bubbling and cratering
• refractory at stoneware temps