One figure decides what a body is called
Water absorption is the property that sorts fired ceramic bodies into classes. It measures how much water a fired body takes up when it is tested in a defined way, and the result is the number the trade uses when it calls a body vitreous, semi-vitreous or something else again. The name is a consequence of the figure, not the other way around.
That is why a phrase like vitreous china is worth less than the number behind it. The phrase is a category. The number is evidence about a specific body, and it is the only part of the description a buyer can check against a document rather than against a catalogue word.
How the figure is obtained
Absorption is measured by taking a fired sample, drying it, weighing it, saturating it under controlled conditions and weighing it again. The difference between the two weights is expressed as a percentage of the dry weight. The conditions and the method belong to the standard the test is carried out to, which is why the report has to name that standard and the testing house.
Two consequences follow. First, the figure is about the sample that was tested, not about every piece in a firing or in a year of production. Second, a figure without a named method is not comparable to another figure, because a different method can produce a different result on the same body. Absorption results travel in reports, not in sentences.
Why firing sets the figure, not the recipe alone
A fired body is dense because it has been brought to a temperature at which the material fuses and its open pores close. The density that gives a low absorption figure is created in the kiln, so the firing cycle does as much work as the body formulation. A well-formulated body that is not fired properly still ends up more absorbent than the specification intends.
This is the reason production control and absorption results are connected. A plant that controls its firing can hold a body property consistently, because the same variable is controlled at every firing. A plant that buys in fired parts cannot control that variable at all, and can only report what it was given.
Our own bodies are fired in our own tunnel kiln at Chaozhou, with casting, glazing, firing, QC and export under one roof in the same plant. The factory was established in 2021, covers 51,000 m² and employs 285 people. Every model in the range, across all 89 codes, is vitreous china; there is no second body specification elsewhere in the catalogue.
What the classes are for
The classes exist so that a buyer and a supplier can agree on a body without describing it every time. They also let a market or a specifier set a floor: a clause can require a body class rather than a brand, and any bidder who meets it can bid.
- A denser, less absorbent body is what a hostile wet environment calls for, because a body that stays closed is a body that does not take on water.
- The class names themselves vary between markets and standards, so a name from one standard is not automatically transferable to another.
- A named class in a specification means little without the test standard that defines it, because the class boundary is set by that standard.
The practical advice is to specify the property and the standard that defines it, then ask for the report. A specification that names only a class leaves the supplier to choose a standard, and that choice can be the difference between a checkable claim and a sentence.
The one figure we publish
Our published AS 1976 test report records water absorption of 0.14%. The report is open on our downloads page, without a login or a form, so that the figure can be read against the method rather than taken on trust.
Read it as what it is. It is one report, on the sample that was tested, issued by the testing house named on the report. It is not a promise about every firing, and it is not a market approval. Where a market needs an absorption result for a specific model, that is a request against that model, and we will send the matching file or say plainly that it is not available yet.
What a low figure does not do
A low absorption result answers one question about one body property. It does not answer the questions a project has to answer, and reading more into it is how specifications go wrong.
- It does not approve the fixture for a market. Approval is a process tied to a model and a market, such as CE on the construction-products route for the EU or WaterMark in Australia.
- It does not describe the glaze, the rim, the flush or the mounting, all of which are recorded separately per model.
- It does not tell you what the fixture emits, which is a different test and a different report.
- It does not stand in for factory quality control, which is what keeps a property repeatable across a year of production.
Where a project is concerned with what the fixture emits rather than what it absorbs, we publish SGS VOC test reports for two models in the range. Where it is concerned with the management system behind the plant, the plant holds ISO 9001. These are separate documents for separate questions, and none of them substitutes for another.
How to ask for the right document
An absorption request that says only “send your certificates” will get a bundle, most of which will not answer the question. Three lines get the file that does.
- The property, named: water absorption.
- The standard the result has to be reported against, because the figure is only comparable within one method.
- The printed model codes the answer has to cover, so the reply is about your order rather than about the catalogue.
Ask for the same three things on every body property and the reply becomes a list of file names rather than a paragraph about quality. That is easier to check, easier to file with the order, and easier to defend if a question is raised later.
Frequently asked questions
What is water absorption in ceramic sanitaryware?
It is the share of its own dry weight that a fired body takes up when it is saturated under a defined test method. The figure says how dense and how closed the fired body is. It is one of the few body properties a buyer can ask for as a number and check against a document.
What figure do you publish?
Our AS 1976 test report records water absorption of 0.14%. The report is open on our downloads page with the catalogues and drawings. It covers the sample that was tested and it names the testing house, so the figure can be read against the method rather than taken as a general claim.
Does absorption decide the class name of a body?
Yes, within a given standard. The class boundary is set by the standard, and the absorption result is what places a body either side of it. This is why a class name without the standard behind it is weaker evidence than the figure itself, and why specifications should name both.
Does firing change the absorption figure?
It sets it. The density that produces a low figure is created in the kiln, so the firing cycle is as important as the body formulation. A body fired away from its intended cycle ends up more absorbent than the specification expects, which is why the figure is a production property as well as a material one.
Is every model in your range vitreous china?
Yes. All 89 models are vitreous china, covering two-piece and one-piece WCs, wall-hung and back-to-wall pans, smart toilets, bidets and accessible suites. There is no second, lower body specification elsewhere in the catalogue, and the bodies are fired in our own tunnel kiln.
Does a low figure mean the toilet is approved for my market?
No. Approval is a separate process tied to a model and a market, and the body is only part of what gets tested. Tell us the model and the market and we will send the documents we hold for that route, and say plainly where a document is not available.
Related on this site
Documents and certificates
Related reading
- What vitreous china describes
- Reading a sanitaryware specification sheet
- What a Wall-Hung Pan Hangs On