midterm exam Flashcards
(156 cards)
1
Q
BTU
A
British Thermal Unit
2
Q
One ___ is the amount of ___ required to raise ___ ____ of ____ ____ _____ _____.
A
BTU heat one pint water one degree Fahrenheit
3
Q
formula for combustion
A
C + O2 (+ kindling heat) = CO2 (gas) + Heat (released as byproduct)
4
Q
_____ must be converted into a ____ before combustion will take place
A
fuels
gas
5
Q
The ___ the ____ in relation to the ____ of the combustible material, the ___ and ___ the fuel will burn
A
larger surface area volume easier hotter
6
Q
Specific kilns are designed to burn ____ _____ and there are many different designs to accommodate differing ____.
A
specific fuels
fuels
7
Q
____ ____ measure ___ ___, which is a measure of a ____ and _____ relationship.
A
Pyrometric cones
work heat
time
temperature
8
Q
____ is achieved when there is enough air (oxygen) for complete combustion of the provided fuel.
A
oxidation
9
Q
___ is achieved by cutting back the air supply so there is not sufficient oxygen present for the complete combustion of the fuel.
A
reduction
10
Q
Grade of hard brick that we use for cone 8-10 kilns
A
2600F/1427C
11
Q
The insulating value of soft brick is ____ to ____ times that of hard brick.
A
three to five
12
Q
Size and temperature rating for our soft brick:
A
brick #26
2600F/1427C
13
Q
The ____ shelves for the gas kilns should not be fired past cone ___ or they ___.
A
mullite
10
will warp
14
Q
Kiln wash recipe
A
50% flint + 50% EPK
15
Q
Avoid using ____ products
A
asbestos
16
Q
Formula for Kaolinite
A
Al2O3·2SiO2·2H2O
17
Q
____ and ____ make up close to ____% of the earth’s crust.
A
Silica
Alumina
75
18
Q
Silica chemical formula
A
SiO2
19
Q
Silica makes up ___% of the earths crust
A
59.14
20
Q
Alumina chemical formula
A
Al2O3
21
Q
Alumina makes up ___% of the earths crust
A
15.3
22
Q
Iron chemical formula
A
Fe2O3 + FeO
23
Q
Iron makes up ____% of the earths crust
A
6.88
24
Q
Two types of rock that we are concerned with
A
metamorphic and sedimentary
25
metamorphic rock is altered by ___, ____ and ___
erosion, heat and pressure
26
sedimentary rock is ____
redeposited in layers
27
____ is the chief agent of geologic change
water
28
Difference between physical change and chemical change
With physical change there is a physical action that is happening; with chemical change there is no physical action required
29
Five examples of physical change
```
plate tectonics
freeze/thaw
glaciation
action of plants growing and other biological activity
wind
```
30
Example of chemical change
dissolving
31
Chemical change:
| Why is dissolving important?
it is a chief agent in clay formation
32
Chemical change:
| What is 'dissolving'?
the chemical action that leaches soluble salts out of rock and makes the oceans continually saltier.
33
Three types of feldspars:
Orthoclase
Albite
Anorthite
34
Chemical formula of orthoclase
K2O·Al2O3·6SiO2
35
Chemical formula of albite
Na2O·Al2O3·6SiO2
36
Chemical formula of Anorthite
CaO·Al2O3·2SiO2
37
Four impurities that make found clay unusable
alkalies
lime
sand
too much organic matter
38
8 tests to determine usefulness of clay
* Test for soluble impurities
* Test for excess sand or other mineral fragments
* Test for lime
* Test for plasticity
* Test for water of plasticity and for dry shrinkage
* Test to determine firing range and fired colour
* Test for shrinkage and absorption
* Deflocculation test
39
In terra sigillata, the usual weight ratio of clay to water is
4:10
40
4 steps to make terra sigillata
o ball mill (not required)
o allow slip to settle for a minimum of a day
o water and suspended carbonaceous matter is decanted off
o top third of clay slip is skipped off for use
41
my claybody recipe
```
6 barnard clay
6 redart clay
18 OM4
20 goldart clay
50 lincoln fireclay
```
42
what does barnard clay do
flux
adds some plasticity
colourant - very dark brown to black once fired; high iron content; cheaper than using iron oxide
43
what does lincoln fireclay do
highly refractory - allows for high firing temperature
filler
adds some plasticity
44
what does goldart clay do
main plasticizer
gives strength
affects porosity - not porous when fired
45
what does OM4 do
adds plasticity
46
what does redart clay do
flux
colour - high iron content
plasticity
47
name of my clay
black stoneware
48
wet to dry shrinkage of my clay
6.2%
49
wet to fired shrinkage of my clay
13.2%
50
which of our feldspars is the orthoclase
custer
51
which of our feldspars is the albite
kona
52
which of our feldspars is the anorthite
we dont normally have one
53
two things that contribute to clay plasticity
organic matter
| bacteria
54
outline the decomposition of feldspars, eg orthoclase
K2O·Al2O3·6SiO2 +H2O ---> Al2O3·2SiO2 +H2O (clay mineral) + K2O(SiO2) (soluble alkali which is carried off in water) + SiO2 (in solution or in the clay)
* the clay can withstand high temperatures due to the leaching out of the soluble alkaline fluxes (K2O, Na2O, CaO) which would otherwise lower the melting temperature
55
"definition" of plasticity
clay when wet will tend to hold any form which is given to it
56
what are the most important qualities of clay (2)
plasticity and permanency
57
characteristics of primary (residual) clay (5)
```
formed close to parent rock
originate from beds of more or less pure feldspar
coarse particle size
relatively non-plastic
relatively pure
often found in irregular pockets
```
58
examples of primary clays (2)
most kaolins
| north georgia kaolin
59
characteristics of secondary (sedimentary) clay (4)
have been transported from original site, usually by water
deposits have usually come from several sources - chemically more complex
more common than primary clays
tend to be much finer grain than primary clay
relatively plastic
60
example of secondary clay
common red clay
61
completion of drying happens in the kiln until what temperature
100C
62
what temperature does the chemically combined water begin to be driven off at in the kiln
350C
63
once clay has been fired to ____C all the chemically combined water has been driven off and the piece cannot be slaked down into clay again
500
64
what happens to the mineral components of the clay after 500C in the kiln
they are now in oxide form
65
at what temperature does quartz inversion happen
573C
66
what happens at quartz inversion
in heating: quartz changes from alpha to beta
| in cooling: quartz changes back to alpha
67
what should happen with the kiln firing at quartz inversion
in both heating and cooling the kiln should be fired very slowly to avoid cracking
68
cooling cracks are called ____ and are characterized as ____
dunting
| fine hairline cracks that may not be very visible
69
explain a heating crack
shows up as a crack that is widened during the firing and is more visible than a cooling crack
70
vitrification is the gradual ____ and ____ and finally ____ of the clay body
hardening
tightening
glassification
71
what are mullite crystals and when do they form
form around cone 1
| needle-like crystalline structures lace the clay together giving it more strength
72
porcelain clay bodies ____ at about cone __ to __
vitrify
| 10 to 15
73
stoneware clay bodies ___ at about cone __ to __
vitrify
| 8 to 11
74
midrange clay bodies ____ at about cone __ to __
mature
| 2 to 8
75
earthenware clay bodies ____ at about cone __ to __
mature
| 05 to 1
76
5 kinds of kaolin we have
```
Edgar plastic kaolin (EPK)
tile six
pioneer
grolleg
helmer
```
77
Ball clay we have
OM4
78
What does the term fireclay refer to
the refractory-ness of the clay. withstands high firing temperatures and is usually added to clay bodies for this purpose
79
a clay which resists deformation below ____C is considered a fireclay
1500
80
fireclays we have (2)
plainsman buff
| lincoln
81
saggar clay we have (1)
xxx saggar
82
stoneware clays we have (3)
goldart
palestone
redstone
83
earthenware clay we have (1)
redart
84
slip clays we have (4)
barnard slip
alberta slip
helmer kaolin
ravenscragg slip
85
What is a clay body
a mixture of clay and other earthly substances which are blended to achieve a specific ceramic purpose
86
what is the purpose of temper
to reduce shrinkage and warping
87
what is an example of a temper
grog
88
what is grog made from
sand, or ground up fired ceramics
89
seven reasons to blend clays are to adjust
```
plasticity
strength
firing temp
shrinkage
colour
texture
glaze fit
```
90
what do plastics do in a clay body
add plasticity and workability
91
what are the plastic components of a clay body
the clays
92
what do fillers do in a clay body
decrease shrinkage in drying or adjust glaze fit
93
three examples of fillers in a clay body
grog
flint
calcined clay
94
what do fluxes do in a clay body
control the fusion point of materials
95
example of a flux in a body
feldspars
96
what is usually added to throwing clays
tooth or texture in the form of fine to course materials such as sand, grog, or molochite (ground up fired porcelain)
97
for increasing plasticity, ____ can be added in small amounts but will cause the clay to be sticky
bentonite
98
casting clays have a ___ mixed in them which makes it so that ______________
deflocculant
| the clay can be made liquid and fluid with much less water than for normal plastic clay
99
two examples of deflocculants
sodium silicate
| darvan #7
100
five important considerations for designing slips
it will suitably cover the ware in a dense coating of the desired colour
it will cling to the ware during shrinkage that accompanies drying and firing
it vitrifies or hardens at a temperature similar to or slightly lower than maturing temperature of the clay body
it will survive under the glaze coating without becoming dissolved in the glaze
it will not make the glaze crack or peel (shivering)
101
what does 'fit' mean in terms of slips
the slip will stay on the surface without flaking off after firing
102
what is the best way to ensure a slip will always fit
always apply it to leather hard clay
103
six categories of materials that go into slips
```
clays
fluxes
fillers
hardeners
opacifiers
colourants
```
104
the clay content of a slip will usually total between __% and __%
40 and 70
105
what clays are usually used for white slip
kaolin and ball clay
106
in slip, ___ clays with ___ in them can be used for earthier colours
darker
| iron
107
the flux used in an engobe will vary with the _____ and possibly the _____
maturing temperature
| colour requirements
108
what may be used as a flux for higher temperature slips (2)
feldspars or calcium (whiting)
109
what may be used as a flux for lower temperature slips (2)
frits or sometimes talc
110
what filler is usually used in slip
silica
111
what does silica do in a slip (3)
lessens shrinkage
lends a desireable property of hardness to the fired slip
increases likelihood of a good glaze fit because it has a low coefficient of expansion
112
how much silica is usually added to a slip
15 - 30%
113
what does a hardener do in a slip
makes slip harder when dry to avoid flaking off during kiln loading
114
what can be used as a hardener in a slip (3)
borax, gum arabic, or CMC gum
115
with regards to slip, what does opacity refer to
how well the slip covers the ware
116
what is the most common opacifier in slip
```
ziconium oxide (zircopax or superpax)
tin oxide works better but is more expensive
```
117
what can kaolin sometimes do in terms of opacity
its refractory nature will allow it to lend opacity
118
how can slips be coloured (3)
mineral colouring oxides
commercial stains
taking advantage of the clay itself
119
why must coloured slips be covered with a clear glaze
to achieve the richest colour
120
what is a good way to get a food safe coloured liner in pots
using clear food safe glaze over coloured slips
121
____ is a latin term meaning "sealed earth"
terra sigillata
122
engobes: what colour does 2% iron oxide produce
light tan
123
engobes: what colour does 4% iron oxide produce
brown
124
engobes: what colour does 6% iron chromate produce
dark brown
125
engobes: what colour does 1% iron chromate produce
light grey
126
engobes: what colour does 2% iron chromate produce
medium grey
127
engobes: what colour does 1% cobalt oxide produce
medium blue
128
engobes: what colour does 1% cobalt oxide and 2% iron oxide produce
grey-blue
129
engobes: what colour does 3% copper oxide produce
medium green
130
engobes: what colour does 10% vanadium stain produce
yellow
131
engobes: what colour does 6% manganese dioxide produce
purple-brown
132
engobes: what colour does 3% granular manganese produce
speckled brown
133
engobes: what colour does 6% rutile produce
creamy tan
134
engobes: what colour does 3% iron oxide, 2% cobalt oxide, and 2% manganese dioxide produce
black
135
what is a kiln
a kiln provides a method of successfully containing and elevating the temperature and firing atmosphere of a ceramic to particular levels
136
6 changes in a clay body that firing achieves
- making it impervious to being re-slaked in water
- heating to maturing or vitrification temperature
- melting or fusing a coating or glaze materials onto the surface of the ware to seal it and/or provide decoration
- providing a means of regulating the amount of oxygen in the atmosphere in order to affect changes in the colour and textures of clays and glazes
- providing enough insulating properties in order to allow the work to be heated and cooled appropriately and safely
- providing a closed environment to allow the introduction of 'atmospheric' firing additives such as soda, wood, and salt
137
It is probable that heating clay to make it ceramic was developed independently at different times in various areas of the world, ___ ____ often produces different types of invention to suit the particular need of a given culture
geographic isolation
138
types of kilns (9)
```
early kilns:
- open pit firing
bank kilns
freestanding kilns
- modern jingdezhen Kiln (china)
- asian climbing chamber kilns
modern kilns:
- updraft kilns
- downdraft kilns
```
139
notes on open pit firing (6):
- low temperature (~800C). earthenware is the only clay that will mature
- often terra sigillata types of slips applied (and burnishing) to help seal surface and decorate
- work was initially dried in the sun and then placed in a pit on top of, and then covered by, fuel. whole thing is covered by broken shards of ceramic to provide insulation
- red iron oxide (Fe2O3) converts to black iron oxide (FeO)
- carbon impregnates surfaces - usually no glaze
- high breakage rate, open bodies are best as they take the thermal shock involved
140
notes on bank kilns (5):
- took advantage of the fact that hot air rises. these retained heat and reached higher temperatures
- a draft created by the rising of hot air pulled oxygen over the fuel, providing more thorough combustion
- control of heat building up and control of oxidation/reduction was possible
- earth walls retain the heat and allow slower cooling which meant more pots survived the firing
- first dampers were seen which affected the amount of oxygen in the kiln and slowed cooling
141
notes on freestanding kilns (8):
- could be constructed where and when needed, didn't need to find a riverbank or hill.
- developed to further refine control over temperatures
- made of fired brick
- ceramics and metalsmithing developing technologies to achieve higher temperatures
- could be modified easily
- beginnings of multiple chambers for various purposes
- insulation as well as control over air and fuel entering the kiln become more sophisticated
- developed rapidly in europe, middle east, and asia
142
types of freestanding kilns (2)
modern jingdezhen kiln (china)
| asian climbing chamber kilns
143
types of early kilns (1)
open pit firing
144
types of modern kilns (2)
updraft
| downdraft
145
notes on modern jingdezhen kiln (4):
- freestanding, based on bank kilns the floor slanted upwards from firemouth to chimney (updraft)
- work was fired in saggers (porcelain) and freely (stoneware)
- saggers and freestanding pots act as bag wall. different temperatures are achieved in various parts of the kiln and are loaded according to where it needs to be fired. porcelain in saggers at the front and loose pots in the back
- kiln design produces a venturi effect near the flue
146
what is a venturi effect
concentrates air flow
147
what is a bag wall
direct how air is going to flow through the kiln.
low wall = heat going directly through
high wall = heat has to go all the way up and then down and through to get out the flue
148
notes on asian climbing chamber kilns ():
- by song dynasty climbing chambered kilns were common
- saggers were used to protect the work from ash and flames and to direct flame
- one chamber provided heat transfer to the next - efficient use of fuel
- downdraft design, provides more even heating
- fuel is introduced to each chamber in line, as it needs to be fired
- not portable; designed and built to last a long time
149
ways to ensure efficient use of resources when firing (8)
- always fire well packed, full kilns
- keep the temperature to between cone 9 and 10 in reduction gas firings
- explore single fire methods
- try to use lower temperature technologies to save fuels
- cull your work and only fire the best pieces
- work as a community and share resources
- use technology to test your glazes etc first
- gas is still cheaper than electric so bisque in gas
150
which updraft kilns do we have (3)
alpine
sagger kiln
raku
151
notes on updraft kilns (5):
- gas burners enter at the bottom or underneath, the heat rises through ware
- oxidation and reduction are controlled by adjusting the air and gas that enters the kiln. dampers are used and alpine has forced air burners
- tend to be hotter at the top and cooler on the bottom
- advantage is that they do not require a tall chimney to operate
- can be relatively portable
152
which downdraft kilns do we have (3)
car kilns (dont have anymore!)
soda
caternary arch
153
notes on downdraft kilns (7):
- provide more even heat distribution
- chimney is usually large and tall
- when chimney becomes hot it creates a passive draft and draws air through burner ports (secondary air)
- primary air is air that enters into combustion at the back of the burners and can be precisely controlled
- dampers at the back of the kiln control the rate of the draft through the kiln
- opening the dampers allows more air in - oxidation
- closing the dampers restricts air - reduction
154
____ air is air that enters into combustion at the back of the burners and can be precisely controlled
primary
155
when chimney becomes hot it creates a ____ _____ and draws air through burner ports (_____ air_
passive draft
| secondary
156
downdraft kilns are often preferred over updraft because (4)
- more even heat in the kiln
- forced air burners are not necessary
- oxidation and reduction are more easily controlled
- efficient, large kilns are possible
