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Sanitary ware

A type of porcelain zircon-glazed ceramic that includes bathtubs, sinks, toilets, etc.

Key phrases linking here: sanitary ware, sanitaryware - Learn more

Details

This is a very large industry worldwide, second only to ceramic tile in clay and energy use. The knowledge of how to make sanitaryware can be found on every industrial continent. Although a lot of it is made in China (e.g. Chaozhou is a small city in Southern China that has hundreds of sanitary ware factories) many other countries have very highly developed processes and innovative products (we are impressed by many in the Middle East).

Most sanitary ware is fired at high temperatures from porcelain bodies resembling the standard 4x25 recipe (feldspar, kaolin, silica, ball clay) and is glazed using zircon opacified feldspar-based recipes. The manufacture of sanitaryware pushes many ceramic processes to their limit (thick casting, high mass drying and firing, thick glaze layers, highly deflocculated slips, etc.) and product loss or defects is common. Many of the factories in the third world that make sanitary ware are less automated and use lower-quality materials but still very dependent on supplier technical support (some have no technical people on staff, any of the requests we get for technical assistance come from these types of companies).

Much technology goes into this industry and its modern form is barely recognizable when compared to a few decades ago. Many other advanced products and applications of porcelain have grown out of the creativity and attention to detail of the sanitaryware industry.

Related Information

Oversize particles in a typical manufactured porcelain body


Example of the oversize particles from a 100 gram wet sieve analysis test of a powdered sample of a porcelain body made from North American refined materials. Although these materials are sold as 200 mesh, that designation does not mean that there are no particles coarser than 200 mesh. Here there are significant numbers of particles on the 100 and even 70 mesh screens. These contain some darker particles that could produce fired specks (if they are iron and not lignite); that goodness in this case they do not. Oversize particle is a fact of life in bodies made from refined materials and used by potters and hobbyists. Industrial manufacturers (e.g. tile, tableware, sanitaryware) commonly process the materials further, slurrying them and screening or ball milling; this is done to guarantee defect-free glazed surfaces.

Crawling sanitary ware glaze sourcing Al2O3 from only feldspar


The original recipe had a very low clay content, sourcing almost all of its Al2O3 from feldspar instead. Although the glaze slurry was maintained at 1.78 specific gravity (an incredibly high value) and thus would have had very low shrinkage, it did not stick and harden well enough to the ware. Why? Lack of clay content in the glaze. The fix was to source much more of the Al2O3 from kaolin instead of feldspar. The reduction in feldspar shorted the glaze on KNaO and SiO2 so these were sourced from a frit and pure silica instead (the calculations to do this were done in Insight-live.com). The change also provided opportunity to substitute some of the KNaO with lower expansion CaO. This reduced the thermal expansion and reduced crazing issues.

Over deflocculated slip causes instability in toilet tank


Sanitary ware factories optimize their slips to have the lowest possible specific gravity for production volume reasons. Potters would be happy with 1.7 SG whereas numbers approaching 1.9 SG are common in factories. They often teeter on the edge of issues like this (sections softening causing localize warping) and inexperienced technicians can be unaware of the critical balances needed to prevent loss in production.

Zircon glazes cover well but they have a problem


This sanitary ware tank lid was made in China. Notice how thick the white glaze is being applied to cover the iron containing body below. This is a testament to how opaque a zircon opacified glaze can be. Zircon often causes crawling (likely due to a combination of the effects of its fine particle size on drying properties and its tendency to stiffen the melt). Extra measures and constant attention to detail (e.g. glaze thickness, slurry rheology, avoidance of sharp contours on ware) are needed with such glazes.

Links

URLs https://ceramicninja.com/
Technical information about the production of sanitaryware
URLs https://archvaladares.com/en/
This company has been making handmade Sanitaryware since 1921.
Glossary Slip Casting
A method of forming ceramics. A deflocculated (low water content) slurry is poured into absorbent plaster molds. As it sits in the mold, usually 10+ minutes, a layer builds against the mold walls. When thick enough the mold is drained.
By Tony Hansen
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