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biondoli 04-06-2008 10:25 AM

fireclay or diatomaceous
I finally was able to reach my friend who gave me a bag of white cristal powder (I raised a question on my tread this morning, but I opened a new tread now as it deserves fresh focus)....this stuff is called DIATOMACEOUS.
I thought it was fireclay as it was a left over from his oven....
He told me that you insert/add this powder on top of the dome between the mortar and bricks and it is supposed to fill in when cracks happen.
Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae.
86% silica, 5% sodium, 3% magnesium and 2% iron
Does anybody know about it?
Diatomaceous earth - Wikipedia, the free encyclopedia
I have a 25lb bag so I am going to use it to level the calsium silicate boards and on top of them to fill the gaps and then I'll follow his idea and put some on the dome.
I thought to share this... Ciao Carlo

brokencookie 04-06-2008 03:54 PM

Re: fireclay or diatomaceous
So this is supposed to make the oven self-repairing like a punture proof tire ?

biondoli 04-06-2008 03:56 PM

Re: fireclay or diatomaceous
that's what my friend was told...looking for more info...

brokencookie 04-06-2008 04:12 PM

Re: fireclay or diatomaceous
Here are the physical properties. It looks like it turns to silica ( glass ) when melted. However, the melting point is 1700 degrees C ( 3100 degrees F for others ) I don't think a pizza oven will reach those temperatures. If they did we could cook a 5 second pizza :eek:

March 2001

Amorphous diatomaceous earth
Diatomite, uncalcined
Diatomaceous earth, natural

CAS No: 61790-53-2
RTECS No: VV7311000 SiO2
Molecular mass: 60.8

FIRE Not combustible. In case of fire in the surroundings: all extinguishing agents allowed.

Inhalation Cough. Local exhaust or breathing protection. Fresh air, rest. Refer for medical attention.
Skin Dry skin. Roughness. Protective gloves. Rinse and then wash skin with water and soap.
Eyes Redness. Pain. Safety goggles. First rinse with plenty of water for several minutes (remove contact lenses if easily possible), then take to a doctor.
Ingestion Do not eat, drink, or smoke during work.

Sweep spilled substance into containers; if appropriate, moisten first to prevent dusting. Wash away remainder with plenty of water. (Extra personal protection: P1 filter respirator for inert particles.)


Physical State; Appearance

Physical dangers
Heating the material at high temperatures results in the formation of crystalline silica (see ICSC 0809 Cristobalite).

Occupational exposure limits
TLV (as silica amorphous): 10 mg/m E,I (ACGIH 2000).
TLV (as silica amorphous): 3 mg/m E,R (ACGIH 2000).
TLV: Intended change silica amorphous - insufficient data
MAK: 4 mg/m (Inhalable fraction) Pregnancy risk group: C (DFG 2005).
Routes of exposure
The substance can be absorbed into the body by inhalation.

Inhalation risk
Evaporation at 20C is negligible; a harmful concentration of airborne particles can, however, be reached quickly when dispersed.

Effects of long-term or repeated exposure
The substance may have effects on the lungs, resulting in mild fibrosis (see Notes).

Boiling point: >2200C
Melting point: 1710C
Density: 2.3 g/cm
Solubility in water: none

Typical Applications:
A silica source in the production of calcium silicates, insulation bricks and material in safes, fireproof filing cabinets, etc. Used in the paint, varnish, lacquer, and polish industries. Used as an insecticide in gardens and in swimming pools as a filtering agent.

gjbingham 04-06-2008 05:26 PM

Re: fireclay or diatomaceous
Insecticide and filtering agent! Will it cure baldness?

I never understood where they came up with the "earth" on the name. Is it mined from old sea floor sediments?

brokencookie 04-06-2008 05:50 PM

Re: fireclay or diatomaceous
It is mined near bodies of water or old dry lake beds ( or seabeds). There are two varieties, saltwater and freshwater. The properties of each are a little different. "Diatomaceous earth consists of fossilized remains of diatoms, a type of hard-shelled algae." I checked the properties of the most common varieties and the melting temps are all very high. IMHO there must be something else that could be used as a self sealer. I have used a block sealer in my car that consists of a high copper content silica that becomes "glass" @ aobut 240 degrees F. A self sealing oven is kind of a neat idea but I think it would not be worth the trouble to set it up correctly. As we have seen, the cracks are only important to the builders ego, not the performance of the oven.


Wiley 04-06-2008 08:10 PM

Re: fireclay or diatomaceous
Another bit of useless info on diatomaceous and diatoms: In the open ocean the small algae type organisms have either a calcium or a silca shell. When they die they start the slow descent to the ocean floor. At about 600 ft of depth, calcium goes into solution, literally it desolves into the sea water. The result is the silica based organisms reach the bottom and over eons develop quite thick layers. After even more geologic time some sea floors are lifted above sea level due to tectonic forces and these sediments become "diamomaceous earth". Under a microscope they are quite beautiful and the age of the sediment can be fairly accurately dated by the species of diatom present.

These are spikey little devils and something one really doesn't want in one's lungs (or one's shorts! :-). They kill bugs by puncturing their hard exoskeleton and then they simply dry out, dissicate to death.

See all that college wasn't wasted! LOL


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