Ceramic materials are employed in the ceramic industry to make glazes, stonewares, earthenwares, porcelains, engobes, refractories, structural products, etc. We study ceramic materials at the mineral, chemical and physical levels.
The recipe mixing area of Tony Hansen
Tony's lab work area of mineral and chemical powders for mixing test glazes and clay bodies. Stoneware and earthenware glazes are made from dozens (even hundreds) of commodity industrial mineral powders.
This is what a semi-trailer load (40,000 lbs) of talc looks like
Talc is not nearly as dense as many other materials. If this was silica these pallets would be half this height.
New Zealand Kaolin original container
The original bag of this product in 2014.
Ceramic materials can vary widely in density
A bag of magnesium carbonate beside a bag of feldspar. Although the former weighs 25 kg (vs. 22.7 kg for the feldspar), clearly it is a dramatically lighter (per volume unit) material. Lifting that bag of Mag Carb feels like lifting a pillow!
An example of a 50 lb bag of soda ash (or sodium carbonate).
Soda Ash is soluble and is thus not useful in most ceramic glazes. However that very solubility makes it very useful to control the electrolytics of ceramic slurries. This is the dense variety, non-hydrous.
An original container of manganese dioxide
This bag will give you a clue as to what manganese dioxide is mainly used for.
Original container of Lithium Carbonate
An original container bag of Tricalcium Phosphate
A material storage rack
This material storage area employs a rack to keep pails off the floor so the area can be hosed down easily. The materials in each pail are sealed in plastic bags or the pail is covered with a lid.
Refined 200 mesh materials are not guaranteed to be such
Each of these eight pallets of kaolin are being sampled to screen them for oversize particles. The 50 gram samples needed can be taken without having to open the bags, they are filled through a valve at the top and it can be opened easily. Kaolins and ball clays especially are suspect and body manufacturers must be vigilant about this (each can tell you disaster stories about making product with faulty raw materials containing grit, carbon and iron particles). The samples will be washed through 70, 100 and 150 mesh screens to spot any particles that could introduce grit or fired speckle into the bodies.
Each 50 lb VeeGum bag is packaged in its own box
This is a quality but expensive material!
Raw red burning clay stockpile
The raw Plainsman M2 clay stockpile before it is ground. This is mined in Montana and imparts red color to various middle and low temperature clay bodies. It is a remarkably consistent material.
When both mineralogy and chemistry are shown on a data sheet
Some material data sheets show both the oxide and mineralogical analyses. Dolomite, for example, is composed of calcium carbonate and magnesium carbonate minerals, these can be separated mechanically. Although this material participates in the glaze melt to source the MgO and CaO (which are oxides), it's mineralogy (the calcium and magnesium carbonates) specifically accounts for the unique way it decomposes and melts.
Do not rely on material data sheets, do the testing
The cone 6 porcelain on the left uses Grolleg kaolin, the right uses Tile #6 kaolin. The Grolleg body needs 5-10% less feldspar to vitrify it to zero porosity. It thus contains more kaolin, yet it fires significantly whiter. Theoretically this seems simple. Tile #6 contains alot more iron than Grolleg. Wrong! According to the data sheets, Grolleg has the more iron of the two. Why does it always fire whiter? I actually do not know. But the point is, do not rely totally on numbers on data sheets, do the testing yourself.
Bulk 2500 lb bulk bags of Pioneer Kaolin
The material is much less dense than most other ceramic materials (that is why these bags are so tall). When moved the powder within becomes unstable and they are prone to falling over.
What can you do using glaze chemistry?
There is a direct relationship between the way ceramic glazes fire and their chemistry. Wrapping your mind around that and overcome your aversion to chemistry is a key to getting control of your glazes. You can fix problems like crazing, blistering, pinholing, settling, gelling, clouding, leaching, crawling, marking, scratching, powdering. Substitute frits or incorporate better, cheaper materials, replace no-longer-available ones (all while maintaining the same chemistry). Adjust melting temperature, gloss, surface character, color. Identify weaknesses in glazes to avoid problems. Create and optimize base glazes to work with difficult colors or stains and for special effects dependent on opacification, crystallization or variegation. Create glazes from scratch and use your own native materials in the highest possible percentage.
Do ceramic material powders go bad?
Many minerals are just ground up rocks, they were in the ground for millions of years (e.g. kaolin, feldspars, ball clays, bentonite, calcium carbonate, dolomite, talc, kyanite, wollastonite, etc), so the powders should last millions of years as well. Some are powderized man-made glasses and sintered solids, these are very stable (e.g. frits, stains). Other man-made materials are less stable and can hydrate or oxidize (e.g. carbonate colors, plaster), keep them sealed containers. Some materials are organic (e.g. Gum Arabic) and they can go bad in damp conditions, so keep them in a sealed container also.
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