final exam Flashcards
(136 cards)
1
Q
what is added to a glaze to make it more viscous
A
alumina
2
Q
glaze may be defined as:
A
a glassy coating melted in place on a ceramic body - rendering it smooth, non-porous, and of desired colour and texture
3
Q
molecular formula for salt
A
NaCl
4
Q
how does a salt glaze work (molecular)
A
the sodium (Na) combines with the silica in the clay body to form a durable glassy coating on the ware. The chlorine (Cl) combines with hydrogen to form hydrochloric acid (HCl)
5
Q
what is an oxide
A
a chemical combination of any element with oxygen
6
Q
once a glaze has been heated and fused, it is in ____ ____, even though the materials that went into it may not have been.
A
oxide form
7
Q
molecular formula for lead oxide
A
PbO
8
Q
molecular formula for sodium oxide
A
Na2O
9
Q
molecular formula for potassium oxide
A
K2O
10
Q
molecular formula for calcium oxide
A
CaO
11
Q
molecular formula for magnesium oxide
A
MgO
12
Q
molecular formula for barium oxide
A
BaO
13
Q
molecular formula for lithium oxide
A
Li2O
14
Q
molecular formula for strontium oxide
A
SrO
15
Q
molecular formula for antimony oxide
A
Sb2O3
16
Q
molecular formula for boric oxide
A
B2O3
17
Q
molecular formula for zinc oxide
A
ZnO
18
Q
list the oxides in Group A - Alkaline Earths (fluxes) (11)
A
lead oxide sodium oxide potassium oxide calcium oxide magnesium oxide barium oxide lithium oxide strontium oxide antimony oxide boric oxide zinc oxide
19
Q
molecular formula for aluminum oxide
A
Al2O3
20
Q
molecular formula for titanium oxide
A
TiO2
21
Q
list the oxides in Group B - Alumina (stiffeners) (2)
A
aluminum oxide
titanium oxide
22
Q
molecular formula for silicon dioxide
A
SiO2
23
Q
list the oxide in Group C - glass former
A
Silicon dioxide (silica)
24
Q
which is the only indispensable glaze oxide
A
silica (SiO2)
25
The oxides in Group A are _____ oxides or ____ ____, and act as ____
metallic
alkaline earths
fluxes
26
Group B does two things which lend visual and surface texture to the glass:
stiffens the melt
| inhibits the formation of crystals
27
what happens to glaze at red heat
the volatile materials such as carbon and sulphur are driven off and glaze minerals are all in oxide form
28
description of silica (include role and molecular formula): (8)
- SiO2
- glass former
- only indispensable oxide
- used as a separate ingredient more in high temperature glazes than in lower temperature ones
- as it promotes hard and durable glazes, you want to use as much as possible in the glaze
- low coefficient of expansion, helps glaze fit
- forms the main body of the glaze
- sources are feldspar, clay, flint
29
description of alumina (include role and molecular formula): (6)
- Al2O3
- stiffener
- very refractory, stiffens the melt and prevents crystals from forming
- not too much can be added as it hinders vitrification
- makes glazes viscous and lends strength
- sources are clay and feldspar (kaolin and china clay are usually used because they are white and form clear glaze easier)
30
description of sodium oxide (include role and molecular formula): (7)
- Na2O
- very strong flux, used from low to high temperatures
- enhances brilliant colours (e.g., soda blues)
- has a high coefficient of expansion which causes crazing problems
- does not lend itself to making hard or durable glazes
- does not produce glazes which are chemically inert (can still be somewhat soluble and break down over time)
- tends to add opalescence to glazes due to trapped air bubbles
31
description of potassium oxide (include role and molecular formula): (5)
- K2O
- flux
- behaves very much like sodium oxide in glazes and is often used in combination with it
- similar fluxing power and colour response as sodium oxide, used from low to high temperatures
- has a slightly lower coefficient of expansion than sodium oxide
32
description of calcium oxide (include role and molecular formula): (5)
- CaO
- flux, often the principal flux in high fire glazes
- often combined with low temperature fluxes at lower temperatures
- contributes to hardness and durability
- fairly refractory
33
description of lead oxide (include role and molecular formula): ()
- PbO
| - - get info from rhodes
34
description of barium oxide (include role and molecular formula): (8)
- BaO
- flux, not very active, fairly refractory. used in medium to high temperature glazes
- important in inducing true matness in glazes (if boron is not predominant)
- favours brilliant copper blues as well as celadons and iron blues
- substantial health risk. it is a heavy metal and can poison
- does not accumulate in body tissues so it has to be consumed in quantity to poison
- be on safe side and don't use barium fluxed glazes on interiors of functional wares. barium on outside surface should be tested for leaching to inside.
- can migrate during firing
35
description of magnesium oxide (include role and molecular formula): (4)
- MgO
- flux, high temperature
- unique colour response with cobalt - purple or pink hues
- magnesium carbonate is used in low and medium temperature glazes as a texture promoter (magnesium carbonate is very light and fluffy and when combined in a glazes causes it to shrink tremendously in raw stage. cracked looking glaze is fired to retain the texture)
36
description of strontium oxide (include role and molecular formula): (6)
- SrO
- flux, similar to calcium but slightly more fusible. medium to high temperature flux
- more expensive than calcium
- replacing the calcium or zinc in a glaze with strontium yields superior glazes
- does have some matte inducing properties so it may be used to slightly matte glaze or give a waxy surface
- ferro frit 3292 contains strontium
37
description of antimony oxide (include role and molecular formula): (5)
- Sb2O3
- flux, but not used as a primary flux
- sometimes used as an opacifier
- often combined with lead to produce a low temperature colour called Naples yellow
- significant health risks, not used in class
38
description of lithium oxide (include role and molecular formula): (7)
- Li2O
- flux, low to medium temperature.
- low coefficient of expansion, can help with crazing
- quite expensive in its purest form (lithium carbonate)
- numerous questions as to its safety and solubility in glazes
- induces brilliant blues from copper
- can lend some matte qualities
39
description of boric oxide (include role and molecular formula): (6)
- B2O3
- strong flux, particularly at medium temperatures
- colmanite and gerstley borate are the insoluble forms usually used in glazes
- aids in reducing glaze expansion and promotes good glaze fit
- produces milky opalescent blues with iron
- when combined with lead it can produce smooth durable glazes with long firing ranges (lead borosilicate)
40
description of zinc oxide (include role and molecular formula): (7)
- ZnO
- flux, midrange and high temperature
- used often as a substitute for lead oxide, mostly in combinations with calcium oxide, magnesium oxide, and barium oxide
- high percentages may cause the glaze to resist from the ware during firing
- with iron oxide produces dull tones
- with copper produces turquoises
- with cobalt produces enhanced blues
41
which oxide fluxes are suitable for low temperatures: (3)
- sodium oxide
- potassium oxide
- lithium oxide
42
which oxide fluxes are suitable for medium temperatures: (7)
- sodium oxide
- potassium oxide
- barium oxide
- strontium oxide
- lithium oxide
- boric oxide
- zinc oxide
43
which oxide fluxes are suitable for high temperatures: (7)
- sodium oxide
- potassium oxide
- calcium oxide
- barium oxide
- magnesium oxide
- strontium oxide
- zinc oxide
44
What is the RO column? What is their function? what is their pH?
- element (radical) combined with one atom of oxygen
- melters or fluxes
- alkaline pH
45
oxides in the RO column: (10)
- PbO Lead oxide
- Na2O Sodium oxide
- K2O Potassium oxide
- CaO Calcium oxide
- MgO Magnesium oxide
- BaO Barium oxide
- Li2O Lithium oxide
- SrO Strontium oxide
- Sb2O3 Antimony oxide
- ZnO Zinc oxide
46
What is the R2O3 column? What is their function? what is their pH?
- element combined with oxygen in a ratio of 2 to 3
- not a flux but influences the nature of the melt
- neutral pH
47
oxides in the R2O3 column: (2)
- Al2O3 Aluminum oxide
| - B2O3 Boric oxide
48
What is the RO2 column? What is their function? what is their pH?
- element combined with two oxygen atoms
- glass former
- acidic pH
49
oxide in the RO2 column: (1)
- SiO2 Silicon dioxide
50
what is eutectic?
- when two glaze forming oxides are intimately mixed and subjected to heating, their melting point is usually considerably lower than either of the melting points of the two original materials themselves
- the kinds of oxides present and the relative amounts of the oxides determine the fusion points of glazes
51
What does clay do in a glaze formula (3)
- makes the glaze coat tough
- contributes both alumina and silica
- can help reduce shrinkage
52
sodium oxide fluxes: (3)
- Nepheline Syenite
- Soda Ash (Sodium Carbonate)
- Cryolite
53
Chemical formula for Nepheline Syenite
K2O·3Na2O·4Al2O3·9SiO2
54
Chemical formula for Soda Ash (Sodium Carbonate)
Na2O·CO3
55
Chemical formula for Cryolite
Na2F·AlF6
56
what is nepheline syenite used for (2)
- potassium feldspar at ^6
| - body flux
57
what is soda ash used for (2)
- egyptian paste, shino glaze, raku glaze
| - deflocculant
58
what is cryolite used for (1)
- textured glaze
59
boric oxide fluxes: (2)
- Borax
| - Colmanite/Gerstley Borate
60
chemical formula for borax
Na2O·B2O3·10H2O
61
chemical formula for colmanite/gerstley borate
2CaO·3B2O3·5H2O
62
what is borax used for (2)
- lower fusion point in glaze
| - raku glaze
63
what is colmanite/gerstely borate used for (3)
- fluxing action
- mottled textures and milkiness in glaze
- tends to flocculate glaze
64
calcium oxide fluxes: (5)
- Calcium Carbonate (whiting)
- Dolomite
- Wollastonite
- Bone Ash (Tri-Calcium Phosphate)
- Fluorspar
65
chemical formula for calcium carbonate/whiting
CaO·CO3
66
chemical formula for dolomite
CaCO3·MgCO3
67
chemical formula for wollastonite
Ca·SiO2
68
chemical formula for bone ash/tri-calcium phosphate
4Ca3(PO4)·2CaCO3
69
chemical formula for fluorspar
CaF
70
lithium oxide fluxes: (4)
- Lithium Carbonate
- Lepidolite
- Spodumene
- Petalite
71
chemical formula for lithium carbonate
LiCO3
72
chemical formula for lepidolite
(HO2FO2)KliAl2·SiO10
73
chemical formula for spodumene
Li2O·Al2O3·4SiO4
74
chemical formula for petalite
Li2O·Al2O3·8SiO2
75
magnesium oxide fluxes: (2)
- Magnesium Carbonate
| - Talc
76
chemical formula for magnesium carbonate
MgCO3
77
chemical formula for talc
3MgO·4SiO2·H2O
78
barium oxide fluxes: (1)
- Barium Carbonate
79
chemical formula for barium carbonate
BaCO3
80
strontium oxide fluxes: (1)
- Strontium Carbonate
81
chemical formula for strontium carbonate
SrCO3
82
zinc oxide fluxes: (1)
- Zinc Oxide
83
chemical formula for zinc oxide
ZnO
84
types of glazes: (6)
- low temperature alkaline glazes
- lead glazes
- boron glazes
- bristol glazes
- porcelain and stoneware glazes
- fritted glazes
85
characteristics of low temperature alkaline glazes: (6)
- below cone 2
- sodium, potassium, and lithium fluxed
- developed in egypt, persia, and mesopotamia
- fluid melting, glassy, tendency to craze, brilliant response to colouring oxides, soft, not stable chemically
- require enough alumina to keep them from being soluble
- subject to crawling
86
characteristics of boron glazes: (7)
- commonly made with frits, gerstley borate, or colmanite
- long fluxing range
- colour response similar to alkaline bases
- copper additions produce greenish turquoise
- may give mottled milky appearance to glaze
- iron may give blueish hues
- high boron glazes tend to boil when melting, leaving a mottled surface when cool
87
characteristics of bristol glazes: (4)
- mid-range maturing (cone 2-6)
- usually rely on zinc oxide as their flux
- originally developed as substitutes for lead glaze
- often a zinc/whiting/feldspar combination
88
characteristics of porcelain and stoneware glazes: (11)
- mature over cone 6 or 7
- composed primarily of feldpars
- calcium as primary flux
- higher percentage of calcium helps with transparency
- surfaces are usually bright and durable
- iron impurities give celadons
- calcium contributes to copper reds
- high magnesium may be 'fat' and opaque
- high zinc may give sugary surface
- very suited to function and utility: durable and chemically stable, good interface with clay body, low crazing
- colour response is usually more muted than low temperature glazes
89
hazards of using soluble glaze materials: (6)
- may be caustic
- glaze water contains solubles so water cannot be decanted or removed if it is to perform properly
- soak into ware; can leave the glaze deficient in the soluble material and can change the melt of the glaze
- migrate to the edges of the pieces which may cause glaze surface problems
- may crystallize over time in the wet glaze
- may be hard to store, as they want to hydrate
90
what contributes to glaze opacity: (5)
- nature of the glaze itself, presence of opacifying agents
- under fired glazes
- trapped air bubbles in the glaze
- crystals in the glaze (devitrification)
- opalescence due to a mixture of glasses that have differing indexes of refraction
91
two opacifiers:
- tin oxide
| - zirconium oxide (zircopax, superpax)
92
what contributes to matness in glaze: (4)
- underfired glaze
- crystals on the surface
- lots of alumina
- barium oxide at high temperature
93
drawbacks of matte glaze (4)
- not durable
- scratch easily
- hard to clean
- noisy on tableware
94
three compounds that have been proven to be toxic in glazes
- lead compounds
- cadmium compounds
- barium compounds
95
what is the primary goal of a food safe glaze
- resistance to acids in foods such as tomato, vinegar, and fruit juice
96
colourants that are considered safe additions to liner glaze (4)
- zirconium
- titanium
- tin based whiteners
- iron oxide
97
colourants to avoid in liner glazes: (7)
- nickel
- chromium
- cobalt
- copper
- manganese
- cadmium
- selenium
98
whats the best way to get a strong colour in a food safe liner glaze
- use a coloured slip with a food safe transparent glaze
99
difference between stable and food safe glaze
stable means that it won't break down in the presence of acids in foods, thermal shock, resistance to scratches, etc; food safe means that it will not leach any harmful toxins into the food
100
tests for glaze stability (and fit): (7)
- resistance to acids
- resistance to alkalis
- resistance to thermal shock
- resistance to knife-marking (abrasion)
- resistance to scratching and wear
- resistance to chipping
- suitability for use in microwave
101
sources of colour in glazes: (4)
- colouring oxides and carbonates
- stains
- soluble colourants
- overglaze
102
colouring oxides and carbonates ___ in the molten glaze to impart colour
dissolve
103
iron oxide as colourant (8)
- predominant colouring oxide
- iron in clay body can lend colour to glaze
- red iron oxide (ferric) is the most stable form Fe2O3
- black iron oxide (ferrous) is a stronger colourant Fe3O4
- additions between 1-7% are usual
- 1% gives celadons, 7% tenmokus
- iron is an active flux in glaze and clay
- modifies colours from other oxides and cabonates
104
copper oxide as colourant (9)
- copper carbonate is most common CuCO3
- Copper oxide is stronger CuO
- additions between 1-5% are usual
- where primary fluxes are sodium, potassium, lithium: turquoise
- where primary flux is boron: greenish-turquoise
- where barium is primary flux: brilliant blue-greens
- volatile over cone 8
- turn reddish in reduction
- modifies other oxides, particularly iron, vanadium, chromium
105
cobalt oxide as colourant (5)
- usually cobalt carbonate CoCO3 and cobalt oxide CoO
- additions between .25-2% are usual
- in alkaline glazes: brilliant blues
- where magnesium is flux: purples and pinks
- often modified by iron, nickel, rutile, or manganese
106
chromium oxide as colourant (8)
- carcinogenic
- CrCO3
- additions between .5-3% are usual
- in glaze with no zinc and low lead: greens
- in glaze with zinc: browns
- with tin oxide: red/pinks
- with copper at high temp: blue-greens
- volatile over cone 6
107
manganese dixode as colourant (4)
- manganese carbonate MnCO3 and Manganese dioxide MnO2
- additions between 2-3% are usual
- usually yields purple or browns
- in alkaline glaze: rich purples
108
rutile as colourant (5)
- ore containing both titanium and iron
- additions between 3-5% are usual
- usually produces tan or browns
- produces mottled textures
- glaze stiffener and can cause pinholing
109
ilmenite as colourant (3)
- ore containing titanium and iron
- additions between 1-3% are usual
- granular form induces spotting or specks in glaze
110
nickel oxide as colourant (3)
- green nickel oxide NiO and Black Nickel oxide NiO2
- usually produces browns
- in high zinc at high temperature: blues are possible
111
cadmium and selenium compounds as colourants (2)
- very good spectrum of red colour in low fire lead glaze
| - bright reds and oranges in china paint and enamels
112
vanadium oxide as colourant (5)
- vanadium pentoxide V2O5
- additions between 4-7% are usual
- combined with tin oxide in stain form for mellow yellows
- raw form will cause bubbling in glazes
- expensive and suspected carcinogen
113
antimony oxide as colourant (2)
- used in combination with lead to produce naples yellow
| - affects glaze melt
114
rare earth oxides as colourants (4)
- called lanthides
- praseodymium produces yellowish greens
- neodymium: different colours under different light, usually light blues to mauves
- erbium oxide: real baby pink
115
characteristics of soluble colourants (4)
- dissolve in water
- can enter body through skin when dissolved
- usually include iron chromate, copper sulphate, cobalt sulphate, potassium dichromate, gold chloride
- used in majolica
116
characteristics of glaze stains (4)
- generally safe as they are fritted and do not fume or volatize
- often have a ubiquitous pastel tone
- don't dissolve in the melted glaze so they are generally more opaque than oxides
- can be useful in modifying colours produced by oxides and carbonates
117
characteristics of overglaze
- historically mineral oxides painted over top a white opaque glaze
- in europe: majolica
- in latin america: talavera
118
name and recipe for my glaze
Ayumi Satin Matte
```
3.6 Soda Ash
11 Dolomite
5.5 Whiting
36.4 Kona Feldspar
18 EPK
20 Strontium Carbonate
5.5 Flint
```
119
what does soda ash do in my glaze
- sodium carbonate
| - acts as a melter/flux
120
what does dolomite do in my glaze
- flux: contains both calcium and magnesium
121
what does whiting do in my glaze
- calcium oxide
| - acts as a melter/flux
122
what does kona feldspar do in my glaze
- albite/sodium feldspar
| - has low fusion point
123
what does EPK do in my glaze
- source of silica (glass former)
| - source of alumina (stiffener)
124
what does strontium carbonate do in my glaze
- melter/flux
| - matting agent
125
what does flint do in my glaze
- silica/glass former
126
the calcium and magnesium in the dolomite in my glaze have the following colour responses
- calcium: enhances brilliant colours (eg. bright blues)
| - magnesium: unique colour response with cobalt ( purple or pink hues)
127
what is crazing
- fired glaze coating is shrinking more than the clay body
128
how can crazing be corrected (5)
- choose glaze oxides with lower coefficients of expansion
- increase silica content (doesn't take much, up to 10% total)
- decrease feldspars or any sources of potassium or sodium
- increase boron
- increase alumina
129
what is shivering
- reverse of crazing, the clay body shrinks more than the glaze does
130
how can shivering be corrected (5)
- choose glaze oxides with higher coefficients of expansion
- decrease silica content
- increase feldspars or any sources of potassium or sodium
- decrease boron
- decrease alumina
131
what is crawling
- when the glaze parts (cracks) during melting and leaves bare spots in glaze surface
132
how can crawling be corrected (2)
- wipe down bisqued ware before applying glaze
| - underglazes may cause crawling
133
what is pitting or pinholing
- bubbles in glaze melt that do not heal
134
how can pitting be corrected (7)
- longer firing cycle with slow heating and cooling
- don't overfire
- reduce zinc or rutile
- apply glaze thinner
- add more flux
- soak at end of firing cycle
- fire slightly hotter
135
interesting glaze techniques/processes
- ash glazes
- crystalline glazes
- bone china
- enamels and china paints
- lustres
- decals
- sprigging
- salt/soda glaze
136
starting point for ash/feldspar/clay ratio for ash glaze
2 ash: 2 feldspar: 1 clay
