Earl Krueger on thu 20 nov 03
Depends on what else is in the glaze.
A small amount of most any copper compound
would prevent putrefication. Silver also.
Doubt that iron or cobalt would have any effect.
Zinc? Maybe, maybe not.
Earl...
Bothell, WA, USA
Dave Finkelnburg on thu 20 nov 03
Hi,
I wrote in a post that CMC could decompose in a glaze. It has been
politely, graciously suggested to me off-list that no such thing happens. I
must admit, I have no scientific proof that CMC is the source of the septic
odor I have detected from some glazes after long storage. I think I know
what I know, but I don't want to spread misinformation. So, I must ask,
does anyone else have any hard evidence on this, either way? Is CMC immune
from decomposition? Does it have some anti-fungal, anti-bacterial power?
Or can it decompose? I'd test this right now, mixing a dilute solution, say
0.7% CMC in water, and seeding it with a tiny bit of clay from my reclaim
bucket (boy, does it smell septic!), but I have no CMC in the studio at the
moment.
Thanks for any input!
Dave Finkelnburg, who has been publicly mistaken before and is
living proof it is not a fatal illness...
Fredrick Paget on thu 20 nov 03
I have had a half gallon bottle of CMC solution go bad in my lab. It
became smelly and less viscous .
I added a split pea sized crystal of bluestone (copper sulfate) to a
new batch in the bottle having read somewhere that the copper would
preserve it. New batch is still ok after several months. That is not
enough copper to color any glazes.
It is known that you can kill algae in a lake by putting bluestone in
the water in miniscule amount so I think that this has validity.
Fred
--
From Fred Paget, Marin County, California, USA
fredrick@well.com
Laura Kneppel on thu 20 nov 03
Hi,
I know I read somewhere within the past 10 years about putting one
small drop of formaldehyde in a quart batch of CMC and water which is
then added in small amounts to the glaze. I still have a jar of CMC and
water that I mixed this way several years ago and it's not cloudy or
gunky like you would expect it to be after sitting on the shelf all
that time. I thought I read it in the Chappell book but maybe it was
somewhere else. I'll have to check. Of course be VERY careful with
formaldehyde, they don't put that skull and crossbones symbol on it for
decoration! But it may remind you of your high school biology class.
I'm not sure if I have any glazes on the shelf that have that
"preserved" CMC batch mixed in. I think I used them up and I haven't
mixed any more. But unless I look on the test shelf I won't know! If
there's anything still wet up there, who knows what kind of science
experiment I might be running after all this time!
Laurie
Sacramento, CA
On Thursday, November 20, 2003, at 04:55 AM, Dave Finkelnburg wrote:
> Hi,
> I wrote in a post that CMC could decompose in a glaze. It has been
> politely, graciously suggested to me off-list that no such thing
> happens. I
> must admit, I have no scientific proof that CMC is the source of the
> septic
> odor I have detected from some glazes after long storage. I think I
> know
> what I know, but I don't want to spread misinformation. So, I must
> ask,
> does anyone else have any hard evidence on this, either way? Is CMC
> immune
> from decomposition? Does it have some anti-fungal, anti-bacterial
> power?
> Or can it decompose? I'd test this right now, mixing a dilute
> solution, say
> 0.7% CMC in water, and seeding it with a tiny bit of clay from my
> reclaim
> bucket (boy, does it smell septic!), but I have no CMC in the studio
> at the
> moment.
> Thanks for any input!
> Dave Finkelnburg, who has been publicly mistaken before and is
> living proof it is not a fatal illness...
Edouard Bastarache Inc. on thu 20 nov 03
Hello Dave,
"Protect liquid organic additives with a biocide. Liquid additives
containing
organic matter must also be protected with a biocide to prevent them from
acting as carriers of contamination when they are introduced into the
process (i.e., in liquid glazes in which an aqueous glue such as CMC is
introduced, the glue should be treated with a biocide when manufactured to
ensure its preservation)."(Smart.Conseil)
It probably depends on the type of CMC you intend to use.
Later,
"Ils sont fous ces quebecois"
Edouard Bastarache
Irreductible Quebecois
Indomitable Quebeker
Sorel-Tracy
Quebec
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/
http://perso.wanadoo.fr/smart2000/index.htm
http://www.digitalfire.com/education/toxicity/
----- Original Message -----
From: "Dave Finkelnburg"
To:
Sent: Thursday, November 20, 2003 7:55 AM
Subject: Can CMC spoil?
> Hi,
> I wrote in a post that CMC could decompose in a glaze. It has been
> politely, graciously suggested to me off-list that no such thing happens.
I
> must admit, I have no scientific proof that CMC is the source of the
septic
> odor I have detected from some glazes after long storage. I think I know
> what I know, but I don't want to spread misinformation. So, I must ask,
> does anyone else have any hard evidence on this, either way? Is CMC
immune
> from decomposition? Does it have some anti-fungal, anti-bacterial power?
> Or can it decompose? I'd test this right now, mixing a dilute solution,
say
> 0.7% CMC in water, and seeding it with a tiny bit of clay from my reclaim
> bucket (boy, does it smell septic!), but I have no CMC in the studio at
the
> moment.
> Thanks for any input!
> Dave Finkelnburg, who has been publicly mistaken before and is
> living proof it is not a fatal illness...
>
>
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>
John Hesselberth on thu 20 nov 03
On Thursday, November 20, 2003, at 07:55 AM, Dave Finkelnburg wrote:
> I wrote in a post that CMC could decompose in a glaze. It has been
> politely, graciously suggested to me off-list that no such thing
> happens.
Hi Dave,
CMC, also known as carboxymethyl ether cellulose sodium salt, is an
organic compound. I'd be more than a little surprised if one bug or
another wouldn't consider it dessert. (Speaking of dessert, CMC is what
was used--maybe still is--to make milk shakes thick--yum, doesn't that
just make you want to run out to your local Dairy Queen?? You, of
course, could get the same nutritional mix by drinking a cup of milk,
eating a small bowl of ice cream and a sucking up a tablespoon or so of
CMC--sounds better all the time). Your correspondent may be thinking of
something like Veegum-T which is similar to bentonite--it sounds like
it should be organic (incorporating the word gum) but is really not.
Regards,
John
http://www.frogpondpottery.com
http://www.masteringglazes.com
Craig Martell on thu 20 nov 03
John commented:
>Your correspondent may be thinking of something like Veegum-T which is
>similar to bentonite--it sounds like
>it should be organic (incorporating the word gum) but is really not.
Hi:
It was me, I did it. I'm the guy who butted in. I was thinking of CMC as
a replacement for gum tragacanth which really gets stinky fast. I've been
told that CMC isn't problematic like tragacanth. So, I finally went to
Multi-Kem Corps website and checked it out. It basically says that CMC is
resistant to heat, bacterial, and enymatic decomposition. I guess that
"resistant" means it will still decompose and get stinky. So, Dave was
right with what he originally posted to Clayart.
later on, Craig Martell Hopewell, Oregon
Tom Buck on sun 23 nov 03
Dave F:
Hi! my chem dict says CMC is quite variable, although what we
potters get is probably high-molecular weight stuff. the reaction between
acetic acid (ethanoic acid, CH3COOH) and refined cellulose (woodfibre
usually) takes place in a sodium hydroxide (lye) solution. every so
often along the cellulose polymer chain, an "OH" ending is changed
to -CH2COOH, so we get R-O-CH2COOH which is then rendered neutral by
reaction with NaOH to yield the sodium salt R-O-CH2COONa.
the properties of CMC depends very much on how many OH endings
take on the methylcarboxy radical.
the actual reaction materials are alkalized woodfibre (to make
the cellusose somewhat soluble) and sodium chloro-acetate, yielding
the above product, namely R-O-CH2COONa.
Now, much of the original cellulose polymer pesists in CMC,
and it is well established that there exist in nature cellulose-eating
bacteria/molds otherwise we would be inundated with dead trees, and
other plant life forms. so when conditions are right, CMC on long-standing
in aqueous dispersions will degrade and some lingering lignins (sulfur-
bearing) will be converted into hydrogen sulfide which can be
detected by the human nose at concentrations barely above 10 nanograms
per cubic metre of air, and which can become dangerous at levels below
10 micrograms per cubic metre of air.
So, Dave, you are right, and others are right. Sometimes the CMC
will degrade, sometimes it won't...the difference? the pH of slurry
will be the major factor. If you dissolve the CMC in water, the resultant
pH will be 6.5 - 8.0. When added to a glaze slurry, the pH can vary
widely. And although CMC itself is stable chemically at pH range of
2-10, the bugs might like a slightly acid condition, say 4.5-6.0 to
do their eating. so test the pH of your slurry containing CMC and
see if the bugs will bite in a year or so.
til later. Peace. Tom
Tom Buck ) -- primary address.
"alias" or secondary address.
tel: 905-389-2339 (westend Lake Ontario, province of Ontario, Canada).
mailing address: 373 East 43rd Street, Hamilton ON L8T 3E1 Canada
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