Robert Reeve on tue 20 feb 07
Hi Folks,
As the subject states I'm looking for some input. I have access to a
mountain of flint fire clay and it seems I can sort out a decent castable
recipe. I'm looking to do a multi fuel, roughly 20 cu. ft. arch top. One
question for those familiar with train/coffin kiln lids.... what is the max
span that can be cast in one piece? how much arch rise? Reinforcement ?
I'm thinking to sort of cast this in "leggo" sections (or maybe tongue and
groove would be more accurate) but a one piece arch would change the framing
and casting needs a bit. The castable will be either:
4 pts by volume 1/4" to fines 30% alumina flint fireclay
2 pts coarse fir shavings
1 pt calcium alumina (71%) cement
or
2 pts 1/4" to fines 30% alumina flint fire clay
2 pts 1/2" to 1/4" aggregate 30% alumina fire clay
2 pts coarse fir shavings
1 pt calcium alumina (71%) cement
I'm still brainstorming on the fire boxes which will have adequate
combustion area for wood (bourry style???) as well as ledges and cast
inserts to accommodate oil and separately gas burners. Any thoughts or
pointers would be greatly appreciated.
I went out with my sons (ages 7, 9 and 11) last weekend and we got 10
5gal buckets of fireclay in 45 minutes. Screened 1/4" mesh. Fun for the
boys.... Rainy grey oregon day... but the sun broke out right as we got to
the quarry and stayed till we left. From the summit it looked like the
whole willamette and umpqua valleys were ocean with islands. We thought
ourselves pretty blessed...
Take care,
Robert
Ann Brink on wed 21 feb 07
Hi Robert,
My gas kiln (which I hardly ever fire-electric is too easy)...is made of a
castable mixture. It has a low rise arch which we made by building a plywood
box shaped form which was placed on the hard brick floor of the kiln. I
packed the walls first (there was a metal shell in place) and after the
walls were set up, we made the arch shaped plywood form and propped it in
place and patted the castable over it, to a thickness of aboutabout 6 inches
thick. The galvanized metal shell doesn't get very hot at all. This is an
updraft kiln, btw.
After a while the ceiling was shedding crumbs and I had to face it with
fiber, using wire and fireclay buttons, (actually, golf tee shaped pieces
with a hole in the tip).You can see a picture of the kiln here:
www.impulse.net/~annsart and click on "Gas Firing" . This picture also
shows the large blocks I made to brick up the door.
Lucky you, having all that clay available!
Ann Brink in Lompoc CA
(mostly about pottery)
----- Original Message -----
From: "Robert Reeve"
> Hi Folks,
> As the subject states I'm looking for some input. I have access to a
> mountain of flint fire clay and it seems I can sort out a decent castable
> recipe. I'm looking to do a multi fuel, roughly 20 cu. ft. arch top. One
> question for those familiar with train/coffin kiln lids.... what is the
> max
> span that can be cast in one piece? how much arch rise? Reinforcement ?
> I'm thinking to sort of cast this in "leggo" sections (or maybe tongue and
> groove would be more accurate) but a one piece arch would change the
> framing
>
Ivor and Olive Lewis on thu 22 feb 07
Dear Robert Reeve,=20
You say one of your materials is flint fire clay. This definition =
implies that it contains an appreciable proportion of Silica. If this is =
in the form of Quartz it may undergo phase transformation what can lead =
to breakdown in structural integrity. It might pay to check this point =
out.
Best regards,
Ivor Lewis.
Redhill,
South Australia.
Robert Reeve on thu 22 feb 07
Ivor,
I think in the states "flint" in the term flint fireclay has nothing to do
with its mineralogy but rather the hardness of the clay mineral kaolinite
itself as presented in certain deposits. I think flint in this context is a
comparative term which refers to the nature of the material to split by
conchoidal fracture as does flint - quartzite.
In any case this is an excerpt of the appropriate section of a report on
this deposit as published in 1951 by the usgs.
Quartz (Si0 2 ) is present in some altered tuffs
and volcanic rocks in grains so small that it es-
capes detection with a microscope. Its presence
has been established by X-ray patterns, and in
some analyzed samples its presence is con-
firmed by a higher silica content than that re-
quired by the alumina-silica ratio of kaolinite
or dickite, with which it is associated. In a few
specimens, quartz of microscopic size occurs
as prismatic crystals with well-formed termina-
tions in association with scorodite and mans-
fie1dite. This quartz probably resulted from the
action of hydrothermal solutions on the invaded
rocks. Some of it formed by crystallization of
excess silica liberated when the volcanic glass
was altered to dickite or kaolinite. The silica fdr
quartz in veins associated with the mosaic inter-
growths of kaolinite and dickite, and in the sili-
ceous matrix which surrounds some clay pellets,
was probably transported from its place of ori-
gin to its pre sent position by hydrothermal solu-
tions.
What do you think anything to worry about?
Thanks for the input,
Robert
On 2/21/07, Ivor and Olive Lewis wrote:
>
> Dear Robert Reeve,
>
> You say one of your materials is flint fire clay. This definition implies
> that it contains an appreciable proportion of Silica. If this is in the form
> of Quartz it may undergo phase transformation what can lead to breakdown in
> structural integrity. It might pay to check this point out.
>
> Best regards,
>
> Ivor Lewis.
> Redhill,
> South Australia.
>
>
> ______________________________________________________________________________
> Send postings to clayart@lsv.ceramics.org
>
> You may look at the archives for the list or change your subscription
> settings from http://www.ceramics.org/clayart/
>
> Moderator of the list is Mel Jacobson who may be reached at
> melpots@pclink.com.
>
Ivor and Olive Lewis on sat 24 feb 07
Dear Robert Reeve,=20
No problems there . I thought it wise to comment since our group is so =
diverse with a wide spread of knowledge and experience.
I can understand that highly compressed Kaolinite which gives a =
conchoidal fracture might be likened to flint or quartzite. I would =
expect all clay samples to contain residual minerals within the size =
range of clay particles. It would be unusual if Quartz was not =
represented in such a mixture.
Sounds as thou you have a perfectly good, low cost, resource. Make the =
most of it.
Hope you have many many firings.
Best regards,
Ivor
| |
|
