Jeff Lawrence on sun 26 apr 98
Hello,
Living as I do on part of a 35 cubic kilometer volcanic ash fall, I tried
some glazes out of it. The price was right!
Ball milling the stuff to get it fine, I discovered an intriguing and
puzzling characteristic of this fused-together ash. To wit, it makes the
settlingest stick-to-the-bottom-of-the-buckety glaze look like fluff on the
wind. This stuff sticks to itself like cement. When I milled it wet
overnight, I had to chisel it out of the ball jars in the morning. I tried
milling it dry and that jar is still clogged (not as bad as the wet was but
well worth procrastinating on).
My tests are too pretty to give up on, but I really need a way around this
self-adhesion. Adding the bentonite for my recipe up front had the best
effect -- any other suggestions?
Other data: When I chiseled the first batch from the bottom of the bucket,
it had that thixotropic aspect I've seen in other settled glazes, where you
a jiggled chunk goes to liquid before your eyes, except the ash in its stiff
state was harder.
The analysis by weight percent from a geologists field guide to the area is:
SiO2 78%
Ti02 .08%
Al2O3 2.16%
Fe2O3 1.54%
MnO .04%
MgO .35%
CaO .4%
Na2O 2.9%
K2O 4.48%
Plus you name it in parts per million.
Any theories about why this volcanic ash behaves this way? Any thoughts on
what characteristics this ash shares with calcined kaolin (the previous
champion "settle-out" additive)?
I keep dwelling on some sort of crystalline structure hooks onto the next
chunk over and creates things fast that are heavy enough to settle out.
Maybe I need some other hobbies ...
TIA
Jeff
Jeff Lawrence
jml@sundagger.com
Sun Dagger Design
Rt 3 Box 220
Espanola, NM 87532
ph 505-753-5913
Grimmer on mon 27 apr 98
Jeff,
Try mixing some of the ash with distilled H2O and taking a pH
reading with litmus paper. Perhaps there's some soluble
alkalis in there. Have you tried deflocculating the glaze with
epsom salt or muriatic acid?
steve grimmer
marion illinois
Jeff Lawrence wrote:
>
> ----------------------------Original message----------------------------
> Hello,
>
> Living as I do on part of a 35 cubic kilometer volcanic ash fall, I tried
> some glazes out of it. The price was right!
>
> Ball milling the stuff to get it fine, I discovered an intriguing and
> puzzling characteristic of this fused-together ash. To wit, it makes the
> settlingest stick-to-the-bottom-of-the-buckety glaze look like fluff on the
> wind. This stuff sticks to itself like cement. When I milled it wet
> overnight, I had to chisel it out of the ball jars in the morning. I tried
> milling it dry and that jar is still clogged (not as bad as the wet was but
> well worth procrastinating on).
>
> My tests are too pretty to give up on, but I really need a way around this
> self-adhesion. Adding the bentonite for my recipe up front had the best
> effect -- any other suggestions?
>
> Other data: When I chiseled the first batch from the bottom of the bucket,
> it had that thixotropic aspect I've seen in other settled glazes, where you
> a jiggled chunk goes to liquid before your eyes, except the ash in its stiff
> state was harder.
>
> The analysis by weight percent from a geologists field guide to the area is:
> SiO2 78%
> Ti02 .08%
> Al2O3 2.16%
> Fe2O3 1.54%
> MnO .04%
> MgO .35%
> CaO .4%
> Na2O 2.9%
> K2O 4.48%
>
> Plus you name it in parts per million.
>
> Any theories about why this volcanic ash behaves this way? Any thoughts on
> what characteristics this ash shares with calcined kaolin (the previous
> champion "settle-out" additive)?
>
> I keep dwelling on some sort of crystalline structure hooks onto the next
> chunk over and creates things fast that are heavy enough to settle out.
>
> Maybe I need some other hobbies ...
>
> TIA
>
> Jeff
> Jeff Lawrence
> jml@sundagger.com
> Sun Dagger Design
> Rt 3 Box 220
> Espanola, NM 87532
> ph 505-753-5913
Michael McDowell on mon 27 apr 98
Jeff,
That is an interesting deposit you are sitting on. I'm curious if there is
any speculations as to the source volcano. I'm guessing that with a silica
content of 78% it was a pretty explosive eruption. As I understand it, the
higher the silica content of the ejecting material the more solidly a
volcano seals itself up between eruptions. When enough pressure builds up to
force through this "plug" in a new eruption the results are often quite
explosive. This was more or less the picture I got of it when investigating
the geology and chemistry of the ash from Mt. Saint Helens here in
Washington State. Mt. Saint Helens was offered as an example of a "high
silica" volcano, but it's ash from the 1980 eruption had a silica content
ranging from 62 to 66% in the nine separate chemical analyses I'm looking at
right now from different locations around the Northwestern US. Here is the
analysis you presented:
"The analysis by weight percent from a geologists field guide to the area
is:
SiO2 78%
Ti02 .08%
Al2O3 2.16%
Fe2O3 1.54%
MnO .04%
MgO .35%
CaO .4%
Na2O 2.9%
K2O 4.48%
Plus you name it in parts per million."
However, I do "smell a rat" in the figure you give of 2.16% for alumina. I'm
more inclined that the original analysis probably gave a figure of 12.16%
(analyses of Mt. Saint Helens ash range between 16.31 and 19.69) and the "1"
was lost in transcription somewhere between the experimenter and the list.
If you'll add up the total of all the materials in the analysis you sent us
it totals 90.7. That definitely does leave room for adding 10% to the
alumina amount before I entering the figures in your glaze calculation
software. If it bothers you that this would give more than 100%, don't stew
about it too much. I gather that the experimental process determines the
amounts of the different oxides independently, and there is some margin of
error in each determination. In any case, none of the analyses I've seen for
Mt. Saint Helens ash add up to 100%. Eight of the nine I'm looking at now
are more than 100% and they range from 99.35% to 104.19%. I'm just guessing,
mind you, but this is one I'd bet on. Try plugging it in to whatever
software you use for your glazes and see which is more predictive of the
results you have already. Try comparing the amounts of the various oxides to
the limit formulas for the cone range you are firing to.
If the rest of the figures you report in that analysis are accurate, then
this is quite an interesting deposit. Your figure for calcia of .4% is quite
low compared to my ash with 4.13 to 6.27% calcia. Iron content of your ash
is quite low, at 1.54% compared to my 4.44 to 6.84%. Titania at .08 is also
remarkably low at .08, where Mt. St. Helens ash has .49 to .73% titania.
Chemically this material seems worthy of serious interest. But then you say
there are difficulties with it's mechanical properties.
It "sets up" in the bottom of your buckets, you say. And apparently you have
lost the use of a couple of good mill jars to it as well. Ahh yes, I
remember these complaints from my work with volcanic ash, though it sounds
like yours is even worse. Well I do have one suggestion that has helped with
Mt. Saint Helens ash. That is to take your raw material and "mine the fines"
from it. What I do with my raw ash is mix it up into a very thin slurry with
water, then pour or siphon off only what remains suspended after letting the
slurry settle for one minute. Then more slowly settling out and drying the
"nectar" gives me a far more tractable material. The remainder of the
material which settles quickly (and is about half the weight with my ash) is
destined for my garden soil where it helps provide fresh supplies of
available micronutrients from all those trace elements it contains. Kind of
expensive if you're buying your ash from a ceramic supplier, but if you're
living on top of a deposit as you are or have brought one home as I have,
It's a viable option :-).
Do continue to report on your experiments with this material. If you can
tame it, it could lead to many fruitful outcomes. One other advantage that
you might consider for using it in your glazes, other than it's low cost, is
that over the years it could be the most consistent, unchanging material
you've got.
Michael McDowell
Whatcom County, WA USA
http://www2.memes.com/mmpots
mmpots@memes.com
Ron Roy on tue 28 apr 98
Hi Jeff,
From what I have been able to understand about volcanic ash - there must be
lots of sodium coming out of it - the molecular formula says there is lots.
I suspect - if it had been weathered enough some of the sodium would have
been leached away and it would not be deflocculating your glaze so badly.
You might try "washing" it - as you would wood ash to get rid of the
alkalies - particularly the sodium.
This will raise the melting point of course. The combination of ball clay,
bentonite and Epsom salts would help the glaze as well but it looks like
you need to get some of that deflocculant out first.
You also have to realize that volcanic ash varies according to how fine it
is, how far from the volcano it was deposited and how it has been affected
by rain. The longer the weathering the less solubles will be present. If
your sample came from a lower layer then you can expect it to have more
solubles - from the material above.
If the conditions are dry then not much weathering has gone on at all.
I just read Michaels answer and tend to agree about the total - I get 89.95
- it could be there is something fishy there. If I were using such a
material I would certainly spring for an analysis.
Jeff asked......
>Living as I do on part of a 35 cubic kilometer volcanic ash fall, I tried
>some glazes out of it. The price was right!
>
>Ball milling the stuff to get it fine, I discovered an intriguing and
>puzzling characteristic of this fused-together ash. To wit, it makes the
>settlingest stick-to-the-bottom-of-the-buckety glaze look like fluff on the
>wind. This stuff sticks to itself like cement. When I milled it wet
>overnight, I had to chisel it out of the ball jars in the morning. I tried
>milling it dry and that jar is still clogged (not as bad as the wet was but
>well worth procrastinating on).
>
>My tests are too pretty to give up on, but I really need a way around this
>self-adhesion. Adding the bentonite for my recipe up front had the best
>effect -- any other suggestions?
>
>Other data: When I chiseled the first batch from the bottom of the bucket,
>it had that thixotropic aspect I've seen in other settled glazes, where you
>a jiggled chunk goes to liquid before your eyes, except the ash in its stiff
>state was harder.
>
>The analysis by weight percent from a geologists field guide to the area is:
>SiO2 78%
>Ti02 .08%
>Al2O3 2.16%
>Fe2O3 1.54%
>MnO .04%
>MgO .35%
>CaO .4%
>Na2O 2.9%
>K2O 4.48%
>
>Plus you name it in parts per million.
>
>Any theories about why this volcanic ash behaves this way? Any thoughts on
>what characteristics this ash shares with calcined kaolin (the previous
>champion "settle-out" additive)?
>
>I keep dwelling on some sort of crystalline structure hooks onto the next
>chunk over and creates things fast that are heavy enough to settle out.
>
>Maybe I need some other hobbies ...
>
>TIA
>
>Jeff
>Jeff Lawrence
>jml@sundagger.com
>Sun Dagger Design
>Rt 3 Box 220
>Espanola, NM 87532
>ph 505-753-5913
Ron Roy
93 Pegasus trail
Scarborough Otario
Canada M1G 3N8
Phone: 416-439-2621
Fax: 416-438-7849
Web page: Home page http://digitalfire.com/education/people/ronroy.htm
NgtvSpace on tue 28 apr 98
I dont know about volcanic ash but Denatured Alcohol seemed to do the trick
for me on glazes that have a high percentage of Borax and turn to rock after
mixing. If you are in the R & D mode try it and let me know if it worked.
Lorca
Mudnjoy on wed 29 apr 98
> I discovered an intriguing and
>puzzling characteristic of this fused-together ash. To wit, it makes the
>settlingest stick-to-the-bottom-of-the-buckety glaze look like fluff on the
>wind. This stuff sticks to itself like cement. When I milled it wet
>overnight, I had to chisel it out of the ball jars in the morning. I tried
>milling it dry and that jar is still clogged (not as bad as the wet was but
>well worth procrastinating on).
Hey guys test it as s sculptural filler, it it sticks so great it might be a
new patching material. JOY Waiting for shade to thinset my tile in Tucson.
Michael McDowell on wed 29 apr 98
Jeff,
Most everyone seems to think that there's an electrostatic problem with your
ash settling. But don't throw out the idea you started with, that the shape
of the particles has something to do with it. I once saw a photo taken of
Mt. St. Helens volcanic ash taken through a powerful microscope. The
particles were incredibly jagged. Like burrs almost. Whether or not the
molecular charges are causing the ash particles to clump up, they are quite
likely also locking on to each other mechanically. Quite possibly both
effects are working at once, and that's why you have such a nightmare in
your buckets. Still, you've got several approaches now to try and improve
it's behavior.
Your remark about the "ash on top apparently lacked the mass to hold the
sufficient heat to keep the silica molten" indicates perhaps some lack of
clarity on how ash deposits form. Volcanic ash is molten material that is
ejected under high pressure from a volcano and shot up into the air as
atomised particles. The stuff cools to a solid almost immediately while
still in the air. These plumes of ash can be carried tens of thousands of
feet into the air and travel hundreds of miles before dropping to the
surface. From my experience chasing around Washington State looking for the
best deposits of ash from Mt. St. Helens I know that the ash particles tend
to be large and granular in deposits close to the source. Further away, most
of the larger particles have already dropped out and the ash deposits are
finer in texture. I ended up gathering most of my ash near Ritzville, nearly
300 miles from the volcano. A slight rise in the land there picked up a 2"
accumulation on the surface. From that source, nearly 100% of the material
will pass through a 100 mesh screen. What can you tell us about the particle
size of your deposit?
I'm not sure I agree with Ron Roy's comments on the solubles in your ash.
The soda and potassia are not freely occurring, but bound up in a glass.
They should be no more soluble in your ash than they are in a feldspar,
possibly less so. This is glass. It would be obsidian if it had come out in
larger particles and cooled a little slower. That's where "apache tears"
come from I believe. But I do support Ron's suggestion that you get an
analysis done of this material if you plan to proceed very far with it.
There are many questions in my mind. But you're the one who needs answers.
Try some of the things that have been suggested and let us all know your
results. Then we can have another round of speculations. Excerpts of yours
and Ron's posts follow...
>Date: Tue, 28 Apr 1998 10:01:39 EDT
>From: Jeff Lawrence
>Subject: Volcanic Ash Riddle #1 resolved
>I asked Rob (PhD Chemistry) about the unsettling settling of volcanic ash
>and he punted to Dave (PhD Geology) who seemed to know these very strata
>by heart.
>He ascribed the self-adhesion to the nature of amorphous silica. Since we
>are 20 miles from the Valles caldera (the source for all that Great Plains
>ash) anything that settled here was fresh from the source. The ash on top
>apparently lacked the mass to hold the sufficient heat to keep the silica
>molten. So the silica froze up in a glassy, amorphous state rather than in
>crystals. When you break crystals of silica, like quartz, you end up with
>lots of little bits where all the chemical bonds remain satisfied. When you
>break up an amorphous form, apparently the broken bonds leave big
>unsatisfied charges, attractive to other bits of opposite charge. So, these
>little electric (?) charges make the little chunks want to come together
wet
>or dry. Dave further said smaller batches will probably work in the ball
>mill, and then gave instructions for exactly the butter-churn cullet
crusher
>Richard Gralnik described.
>Jeff Lawrence
>Date: Tue, 28 Apr 1998 10:03:27 EDT
>From: Ron Roy
>Subject: Re: Volcanic ash settling
>Hi Jeff,
>From what I have been able to understand about volcanic ash - there must be
>lots of sodium coming out of it - the molecular formula says there is lots.
>I suspect - if it had been weathered enough some of the sodium would have
>been leached away and it would not be deflocculating your glaze so badly.
>You might try "washing" it - as you would wood ash to get rid of the
>alkalies - particularly the sodium.
>
>This will raise the melting point of course. The combination of ball clay,
>bentonite and Epsom salts would help the glaze as well but it looks like
>you need to get some of that deflocculant out first.
>
>Ron Roy
Michael McDowell
Whatcom County, WA USA
http://www2.memes.com/mmpots
mmpots@memes.com
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