Tom Buck on fri 26 jun 98
Magnesium oxide Mg(II)O the only form of Mg that exists at high
temperature has a melting point of 2800 deg Centigrade (Celsius) or 5070
(+/-) deg Fahrenheit. But this seldom happens in a well formulated glaze
since other ingredients influence the melting point, and bring it down to
the usual highfire range (22-2400 F, 12-1300 C).
In a glaze, the element Manganese undergoes chemical change in a
more complex manner. Potters generally use either Manganese Dioxide
Mn(IV)O2 or Manganese Carbonate, Mn(II)CO3. The MnO2 switches to
Mn(III)2O3 at 535 C 1000 F... this compound sometimes is called Manganese
Sesquioxide. Later, at 1080 C 1980 F, the Mn2O3 changes to the monoxide
(see below).
The Carbonate undergoes a change at 1000 C 1800 F and becomes
Mn(II)O or manganese monoxide, a compound that by itself would melt at
1650 C 3000 F but since it is with other glaze materials it will
participate in the general fusion of the glaze at a lower temperature.
(Data from Condensed Chemical Dictionary and Handbook of Chemistry
& Physics).
Laura, does this help?
Tom Buck ) tel: 905-389-2339
& snailmail: 373 East 43rd St. Hamilton ON L8T 3E1 Canada
(westend Lake Ontario, province of Ontario, Canada).
On Wed, 24 Jun 1998, Laura Conley wrote:
> ----------------------------Original message----------------------------
> James Chappell's book Clay and Glazes list the melting temp of magnesium and
> manganese both at 5072F. I can believe this for manganese, but magnesium???
> Does anyone know if this is correct, and if not what is?
>
> TIA,
> Laura Conley
>
Earl Brunner on sat 27 jun 98
I have heard that metallic magnesium, once lite will burn under water. As a
scout master, in our survival packs while backpacking we carried small bars of
it that a flint imbeded in one side, to start a fire with damp material we
would shave off a small pile of shavings and flakes and strike the flint into
the pile. We could get a fire going this way because the magnesium burned at
such a high temperature.
John H. Rodgers on sun 28 jun 98
-- [ From: John H. Rodgers * EMC.Ver #2.5.02 ] --
Magnesium is so active when burning that it can be placed under water, and
will separate the oxygen atoms from the hydrogen atoms in the water molecule
.. Also, a burning stick of magnesium can be place in pure carbon dioxide and
the intensity of the burning is so great that it will separate the Oxygen
from the carbon and leave black carbonacious soot floating in the air. Co2
extinguishers don not work on burning magnesium.
During world war two, crankcases for aircraft engines were made of magnesium
because of the strength to weight ratio. But an inflight fire in an engine
could be a nightmare because if the metal got hot enough to burn, the fire
could not be put out, and it would burn right off the engine mount and fall
from the airplane, or burn through the wing.
Hard burning stuff, magnesium.
John Rodgers
-------- REPLY, Original message follows --------
Date: Saturday, 27-Jun-98 02:02 PM
From: Earl Brunner \ America On-Line: (brunnerec)
To: Multiple recipients of list CLAYART \ Internet: (clayart@lsv.uky.
edu)
Subject: Re: magnesium & manganese
----------------------------Original message----------------------------
I have heard that metallic magnesium, once lite will burn under water. As
a scout master, in our survival packs while backpacking we carried small
bars of it that a flint imbeded in one side, to start a fire with damp
material we would shave off a small pile of shavings and flakes and strike
the flint into the pile. We could get a fire going this way because the
magnesium burned at such a high temperature.
-------- REPLY, End of original message --------
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