David Finkelnburg on thu 25 nov 10
Stephani,
It mostly just leaves empty seats on the bus. Great visual, btw!
Most clays have LOI due to organics on the order of less than 2%,
usually less than 1%. It would be hard to observe and measure the effect of
shrinkage due to organic burnout.
Strictly speaking, LOI is a measure of loss in weight expressed as a %
of the starting weight. Since shrinkage does not necessarily involve any
loss in weight I think it makes sense that it is considered separately.
Good playing in clay,
Dave Finkelnburg
http://www.mattanddavesclays.com
-----------------------------
On Thursday, 25 Nov 2010, Stephani Stephenson
asked, "While we are at it, can anyone help me either affirm or reject th=
e
notion that LOI might contribute to 'shrinkage'?" and, "...is LOI describin=
g
a loss in mass or weight only, and not volume?"
Stephani Stephenson on thu 25 nov 10
While we are at it, can anyone help me either affirm or reject the not=
=3D
ion
that LOI might contribute to 'shrinkage'?=3D20
if loss on ignition happens via outgassing but also involves combustion=
=3D
of
organic materials (carbon, sulfur, etc?), right?
So, do those materials 'take up space' in the clay body?
here's my highly scientific analogy.=3D20
If you are following the claybody from when it is moist to when it is fi=
=3D
red
and=3D20
if the the claybody is a bus, and all the elements and compounds are
passengers on the bus...
we know that when water gets up out of it's seats and leaves the bus, the=
=3D
bus gets smaller.=3D20
so does the same thing happen when carbon, sulfur, etc get up and leave t=
=3D
he
bus?=3D20
or do they just leave vacant seats, but the bus size remains the same ?
I.E., is LOI describing a loss in mass or weight only, and not volume?
or is it possible it involves volume, but so miniscule as not to matter=
=3D
.
just wondering if LOI is a factor at all.=3D20
i know, Dave, Vince, Lili, everyone, you are laughing your arses off, in
fact i am not sure exactly where along the path i even came up with this =
=3D
notion!
but I swear, I am prepared for reality....
Stephani Stephenson
who can visualize buses better than electrons....
Stephani Stephenson on fri 26 nov 10
Dave, thanks for the response.
Sooooo , if that is the case, and the seats on the bus are empty but sti=
=3D
ll
present, would the empty seat spaces be considered voids?
If the weight has lessened ,but not the volume,=3D20
then does it follow that absorption and/or porosity , rather than shrinka=
=3D
ge,
would be affected by LOI?
1% -2& is small but could be significant or (possibly?) measurable=3D
.=3D20
I was trying to nudge a claybody in a certain direction with regard to
absorption/porosity as well as shrinkage, so that's the basis of my query=
=3D
.=3D20
Since a lot of the materials in a claybody have varying LOIs including th=
=3D
e
clays themselves,( in addition to the wollastonite/whiting issue), I was
considering what the combined effect might be in selecting materials with=
=3D
the lowest LOI .
The true mystery remains though. Who's driving the bus, and does it have =
=3D
to
stop at ALL railroad crossings, even those long out of use?
Thanks much
thawing out the hummingbird feeders this AM.=3D20
Stephani Stephenson
_____________________
Dave wrote:"......Most clays have LOI due to organics on the order of les=
=3D
s
than 2%,
usually less than 1%........
Strictly speaking, LOI is a measure of loss in weight expressed as a =
=3D
%
of the starting weight. Since shrinkage does not necessarily involve any
loss in weight I think it makes sense that it is considered separately.
Jon Pacini on fri 26 nov 10
Greetings all---Hi Stephanie-----In bodies such as earthenwares that do not
fully vitrify, the open seats left behind by LOI materials contribute to
what give the body part of it's porosity. In Stonewares and porcelains as
the body gets hotter and fuses the open seats collapse or shrink and there
is no porosity.
So LOI materials contribute to both situations ---a large bus with open
seats and a smaller bus.
Best regards
Jon Pacini
Headed up to the spectacular mountains above Palm Desert today, to get
Fred's wood kiln ready for another firing
David Finkelnburg on sat 27 nov 10
Stephani,
I agree with Jon Pacini who expressed it much better than I did. Voids
only affect porosity if they are part of an interconnected network. It's
what happens after the burnout that affects porosity and absorption.
Good nudging that claybody.
Dave Finkelnburg
http://www.mattanddavesclays.com
-----------------------------
On Friday, 26 Nov 2010 Stephani Stephenson wrote:
"....Sooooo , if that is the case, and the seats on the bus are empty but
still
present, would the empty seat spaces be considered voids?...."
Stephani Stephenson on sat 27 nov 10
Thanks so much Jon and Dave!
This gives me a good visual on what is happening and helps me review my=
=3D
thinking.=3D20
Ingredients alone do not determine how the behavior of the bus and the=
=3D
passengers but they are a factor , along with the softening or melting
process ( which is a major factor) .
They are a few of the variables we work with , whether we do so from
instinct, experience or scientific knowledge. I like it when all three
approaches are in sync.
So now I am picturing the bus climbing a long hill. (The water has long b=
=3D
een
'driven ' off.)
As the bus gets hotter it starts to soften and wrinkle a bit, even afte=
=3D
r
those who have left have left, and those who are staying ,are staying.=3D20=
=3D
but that's enough of that.
gotta go walk off the pumpkin loaf and think about adobe/cob loafs.
Stephani Stephenson
http://www.revivaltileworks.com
http://www.revivaltileworks.com/arcilla/
| |
|
