A Brief History of Saggars
Posted by Tom Evans on June 28, 2021
Put basically, the saggar is a deep ceramic box used in industrial applications to hold materials or items while they’re being fired in a kiln or furnace. While they can look relatively simple, the saggar was one of the first items of kiln furniture ever invented and has been through many ups-and-downs during its long existence. We’re here to pay tribute to the elder of the ceramics world and take a look inside the saggar.
The Early Age (Pre-1700s)
The very first saggars were probably created over a thousand years ago for the production of porcelain in the Jiangxi province of China. The purpose of the saggar was to protect the items during firing from direct flames and to prevent wood ash from blemishing the ceramics. Over the centuries the secret of the saggar spread to Japan and other Asian countries before reaching the UK in the 1700s.
The Golden Age (Pre-1950s)
Early saggars were usually handmade items manufactured by individual pottery factories (‘Pot Banks’) for their own use. Each saggar would be made by a team of three. First the Framemaker would form the sides of the saggar (known as the frame) using an appropriately shaped template, a mound of clay and a very large mallet. At the same time, the entertainingly named Saggar Maker’s Bottom Knocker would form the bottom of the saggar using similar equipment. While still wet, the bottom and the frame would then be handed to the Saggar Maker who’d join the components together by hand. The finished saggar would then be dried and fired on top of a kiln.
The saggar was a fundamental part of the growth of the pottery industry in Stoke-on-Trent. The ‘bottle kilns’ of the time largely produced heat by burning coal, resulting in a lot of smoke (hence why most contemporary paintings of the Potteries shroud the land in dark grey clouds). Given this, having the saggar to protect the ware from the dirt and the smoke was essential (especially given that tableware is at least partially meant to be a decorative item).
In the early 1900s, it was found that the life of the saggars could be extended by first firing them to a higher temperature. The need for dedicated high temperature kilns moved the manufacture of the saggars out of the individual ‘pot banks’ and into specialist kiln furniture companies, where the production of saggars really took off.
The Dark Age (1950s – 2000s)
This Golden Age couldn’t last forever though. The introduction of “clean air” legislation in the 1950s meant that many manufacturers had to literally clean up their acts and cut down on the emissions that their kilns were producing. This led to the industry rapidly moving from coal to gas firing, in turn resulting in cleaner kilns producing less smoke, ash and fumes. The issue for the saggar was that this meant that the ware now needed less protection from the kiln atmosphere, reducing the needs for saggar’s tall sides.
The result, oddly enough, was the invention of the batt, a now ubiquitous pieces of kiln furniture that literally started its life as a saggar without the sides attached. The batt was great for manufacturers, providing the same support while requiring a fraction of the materials and workforce to make it, though we imagine there were some Saggar Maker’s Bottom Knockers who were miffed to be out of a job.
As the batt became more popular, the saggar’s prevalence waned. They were now typically used for more specialist applications in more aggressive environments. The writing seemed to be on the wall.
The Renaissance Age (2000s and Beyond)
All was not lost though. As more new technologies and new industries have sprung up over the past decade which require more complicated firing techniques, the saggar has become increasingly relevant to the modern landscape for a large range of reasons:
- Saggars can be used to contain powders, granules, and small components. For example, the parking sensor on your car uses a tiny piezo-electric transducer – these are often fired by the thousand in a saggar.
- Saggars can be used as enclosures, helping to retain the vapors of volatile ingredients as they are processed at high temperatures. Many industrial chemicals such as tin oxide (which is used as an additive during glass manufacture) are made using saggars.
- Saggars can protect objects from contamination. Researchers use saggars made of non-reactive materials such as alumina to hold materials they are testing or that they’re reacting together. Any reaction between the saggar and the contents would invalidate the test result or ruin the material produced.
By far the biggest industry to have recently embraced the saggar is the Electric Vehicle (EV) Battery industry. The production of these batteries requires the use of complex multi-metal oxide active powders. These powders are made by reacting the raw ingredients together at high temperatures, at which point the potent brew of metal salts becomes incredibly corrosive. IPS’ Mullite saggars are used to contain these materials during this calcination process, mullite being used for its non-reactive nature and high corrosion resistance.
With the EV Battery Industry rapidly expanding and seemingly here to stay, it’s fair to say that the legacy of the saggar has been secured for quite some time to come.