Talk:Mullite

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Quote "Researchers recently discovered [1] that potters in the Hesse region of Germany unknowingly used mullite to create crucibles, enabling alchemists to heat their crucibles to very high temperatures. The formula for making it (using kaolinitic clay and then firing it at temperatures above 1100 degrees) was kept a closely guarded secret." Now I admit I have not read the referenced paer but just the quote suggests nothing radical. The knowledge that firing kaolins to high temperatures resulst in the formation of mullite has been very oldTheriac 18:48, 5 January 2007 (UTC)[reply]

Addition

I have added a reference to porcelain.

Confusing Sentences

I am a chemist and I do not understand these sentences: "Unusually, mullite has no charge balancing cations present. As a result, there are three different aluminium sites: two distorted tetrahedral and one octahedral."

Ag2O3 and SiO2 are both charge neutral materials - no additional cations needed. Stated another way, Al and Si are the cations. The second sentence is true, but I don't see how it follows as I don't understand what the first sentence is trying to say.

When I have time later I will try to edit this so it makes more sense, but I thought I would ask here first in case someone more knowledgeable than me knows why the sentence is phrased this way. — Preceding unsigned comment added by JohnCabbage (talk • contribs) 21:40, 30 May 2016 (UTC)[reply]

Another potter finds article fishy

I agree with the comment left on 5th January 2007. Chasing the citations led me to where I believe the [citation needed] argument is sourced: [12], https://doi.org/10.1111%2Fj.1551-2916.2008.02383.

Crucibles from the German region of Hesse have been famous since the Middle Ages due to their exceptional quality, regarded by many as a mystery. We analyzed 50 Hessian and non-Hessian archeological crucibles using SEM-EDS, FESEM, and XRD to investigate their technology and material properties. It was revealed that Hessian crucibles were systematically made of kaolinitic clay with a low flux content, mixed with quartz sand, and fired to temperatures in excess of 1300°C. Primary mullite developed in most of the glass matrix, with secondary mullite in some regions of clay–feldspar relict mixtures. Consequently, the vessels showed superior creep and thermal shock resistance, high-temperature strength, and thermal and chemical refractoriness.

The usefulness of kaolin in clay bodies should be assumed to have been known to ancient potters, who could distinguish between mediocre and exceptional clay. The low flux (adulterants added to let glass melt at lower temperatures) content of the clay from Hesse may have been as relevant to the production of mullite in its fired vessels as the high amount of kaolinite.

I urge a responsible editor to either excise the citation-needed-bearing-clause or to arrive at the truth of this matter. 24.80.197.243 (talk) 16:42, 19 September 2023 (UTC)[reply]