Dave Finkelnburg on fri 2 apr 04
Taylor,
The density difference is real. Clays are about 2.5. Glazes about 2.6
(except for fritted and lead and high rutile or iron glazes). Is the
difference important? That's a personal matter, but I think it's only
important in terms of understanding.
I've gone to the books for the following densities, all in
grams/milliliter:
The density of silica in glazes (quartz) is about 2.65. Note 1
The density of feldspar in glazes is about 2.6. Note 2
The density of whiting (calcite) in glazes is about 2.71. Note 3
The density of kaolin is about 2.6-2.63. Note 2 (also, www.digitalfire.com
uses 2.5, but does not cite a source for this density value)
From these it is clear to me that an "average" high-fire stoneware glaze
(Leach 4321) that contains about 40% feldspar, 30% silica, 20% whiting, 10%
kaolin will have a density of about 2.64. I've used 2.65 and 2.67 in posts
to the list before, because I often use talc (density 2.8) in my glazes.
What dry ingredient density you want to use in Brongniart's formula is
less important than understanding where that number comes from.
Being able to derive the formula is useful to understanding it as a tool
for working with glazes. See my post
http://lsv.ceramics.org/scripts/wa.exe?A2=ind0401C&L=CLAYART&P=R31782
Good glazing,
Dave Finkelnburg
Note 1: "An Introduction to Metallurgy," 2nd Ed., Joseph Newton, 1947,John
Wiley & Sons, Inc.
Note 2: "Manual of Determinative Mineralogy," 16th Ed., George J. Brush,
1926, John Wiley & Sons, Inc. Precise values are 2.57 for potash spars,
2.62 for soda spar (albite).
Note 3: "Handbook of Chemistry and Physics," 44th Ed., 1962, Chemical
Rubber Publishing Co.
----- Original Message -----
From: "Hendrix, Taylor J."
To:
Subject: Re: Relative density
The real question still is this. Is the 7% difference between values
really all that in the real world?
Hendrix, Taylor J. on sun 4 apr 04
Hehehe. Now Professor Finkelnburg, you don't think I would have come to
class without first preparing. I've read your book for sure and now I
know quite well what is and how to use Buggerhead's formula.
Thanks to your goading me into computing my glaze ingredients total r.d.
I use a lot of 3134 (~2.6) and will use a lot of talc and wolly (2.9).
I'm just not sharp on whether a difference is significant or not given
the types of measurements we do in our studios (you) or our newbios
(me). Since I have had to make my own weights for my two pan, I guess I
shouldn't be too worried about it. Still, once a lab rat, always a lab
rat.
Taylor, in Waco
p.s. I use material constants from the Hammar book.
-----Original Message-----
From: Clayart [mailto:CLAYART@LSV.CERAMICS.ORG] On Behalf Of Dave
Finkelnburg
Sent: Friday, April 02, 2004 1:10 AM
To: CLAYART@LSV.CERAMICS.ORG
Subject: Density of dry glaze ingredients
...
Being able to derive the formula is useful to understanding it as a tool
for working with glazes. See my post
http://lsv.ceramics.org/scripts/wa.exe?A2=3Dind0401C&L=3DCLAYART&P=3DR317=
82
Good glazing,
Dave Finkelnburg
..
Pat Southwood on mon 5 apr 04
Hi List,
Still chortling at "Buggerheads formula" Brilliant.
I can't pronounce it either, never mind understand it.=20
My bucket chemistry method is to make up 100 grams of your glaze at the =
correct consistency and then pour it into a measuring jug.
Mine come out at a quarter of a pint of glaze for 100 grams. From that =
you can work out colourant additions.
It's a bit basic, but functional.
Best,
Pat.
pat@southwood4.fsnet.co.uk
www.theceramicartist.com.co.uk
Earl Krueger on tue 6 apr 04
When talking about density of materials are you referring to the weight
of one cubic centimeter of solid material, such as a single crystal, or
the weight of one cubic centimeter of ground up powdered material?
I imagine the two would be different.
Thanks...
Earl K...
Bothell, WA, USA
Just want to be prepared in case I ever take Taylor's correspondence
course.
daniel on wed 7 apr 04
Hi Earl,
> When talking about density of materials are you referring to the weight
> of one cubic centimeter of solid material, such as a single crystal, or
> the weight of one cubic centimeter of ground up powdered material?
>
> I imagine the two would be different.
That's exactly what I was getting at. I'll look up the methods that Taylor
mentioned at some point but for now I'm content to understand that I can't
do this in my garage.
But I will probably have a go at the unfortunately re-monikered Monsieur B.
Head's formula to try to really understand it.
Thanx
D
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