Porcelain in Wood Design - Impression Video
Since 2018 "Alumina Porcelain" represents the second highest level of quality by Holst Porzellan. As a modification of the "High Alumina Porcelain", we have succeeded in implementing the raw material composition formula in order to manufacture this quality level in conventional production facilities. Alumina Porcelain by Holst corresponds to the quality class of hard porcelain. Unlike ordinary porcelain, the kaoline contains about 28% reinforcing aluminium oxide. Although this is significantly less than with our High Alumina, it is still enough to fire the body at much higher temperatures than normal hard porcelain.
In addition to the individual perceptions of brilliance, color and similarity of the articles, the following usage properties represent the essential differences from conventional quality porcelain and thus guarantee users a much higher long-term value.
Product benefits & technical information
Alumina Porcelain was conceived as an improved level of hotel porcelain. Alumina Porcelain is also produced by the two-firing-process. The first firing called bisquit - is made in kilns about 1000 ° C for about 13 hours. The second firing we called glaze-firing heats up to 1320 - 1350 ° C for about 19 hours. Like the classic feldspar porcelain, Alumina also consists of classic raw materials such as kaolin, feldspar and quartz. Due to a special enrichment of additives, the strength and stability is higher than with normal hard porcelain, without losing the hardness of the glaze or body. German technology combined with our German quality management, as well as constant laboratory monitoring of the production guarantee a constant quality level of this porcelain for commercial use.
The combination of aluminium oxide with its eight enrichments of quartz-crystalline minerals and the high firing temperature gives the porcelain body a higher durability and resistance against physical shocks. The edge impact resistance of our alumina porcelain is considerably higher than that of conventional hotel porcelain. Under laboratory supervision and in application of DIN-EN-12980 we have determined the following load limits.
Alumina porcelain - in edge-reinforced hotel quality - is in comparison to..
- Ordinary household porcelain is 888% more stable.
That makes a factor of 9.8 times stronger.
- Asian hotel porcelain in the mono-brand process is 534% more stable.
That makes a factor of 6.4 times stronger.
- European premium hotel porcelain in the two-brand process is 343% more stable.
That makes a factor of 4.4 times stronger.
- German premium hotel porcelain of the highest quality level, 154% more stable.
That makes a factor 2.5 times stronger.
This numbers speak for themselves and document, that our Alumina Porcelain is very much stronger than common feldspar porcelain.
Alumina Porcelain by Holst is a special reinforced hard porcelain. We combine all the positive facts of the high-fired feldspar porcelain and the mechanical stability of Durable or Vitreous China. The water absorption of the Alumina Porcelain is, depending on the type of production, between 0.01 and 0.04%. Alumina Porcelain also meets the scientific requirements of the hard porcelain quality class. By adding a special formula of aluminum oxide and eight other inorganic substances, we achieve a high formation of needle mullite in hard fires at 1,320-1,350 ° C. These thousands of interlocking crystal structures make the body particularly strong. Hence the high edge impact resistance.
It gives critical points such as the edges of the cup, the edges of the mouth, sniffing and handles a much higher stability.
Ovenproof & Thermal shock resistance
For the documentation of thermal shock resistance and oven ability, you will find a one-minute video above, which documents these properties in an understandable and impressive way.
High Alumina can be used without hesitation in all types of ovens, convection ovens, combi steamers, convectomats, etc. up to a temperature of 350 °C. Please note the maximal thermal shock resistance of 180 °C. Coming out of the cooler or fridge, porcelain should not be put into a running pizza oven.
Like normal hotel porcelain also Alumina Porcelain is made from natural, inorganic and mineral-containing raw materials. This means that it has no metallic ingredients which are against any kind of suitability or heating in the microwave. Alumina Porcelain is 100% suitable for microwaves.
Since the introduction of DIN-EN 12875-1, the specification of dishwashing resistance has been strictly regulated. The description of dishwasher resistance is eliminated and substitued by the number of dishwashing-cycles which can be passed of the material. This begins at 125 cycles and then progresses to 250, 500 and 1.000. However, the use of the promise of dishwasher resistance in conjunction with the official pictogram according to DIN requires an expensive and, in our opinion, very dubious test procedure. We therefore voluntarily guarantee our white, unfinished alumina porcelain a general dishwasher resistance of at least 3.000 wash cycles. Decors, logos and other types of finishing are excluded.
Cut resistance, glaze hardness and abrasion resistance
Like all other types of hotel porcelain or hard porcelain, Alumina Porcelain basically has a glaze hardness of 6 Mohs. All porcelain manufacturers who still describe their surface or glaze hardness with 8 Mohs have not been familiar with the conversion of the DIN-standard EN-15771 since 2010! 8 Mohs does not exist for tableware porcelain. Depending on the measuring point and the number of pinholes Alumina Porcelain - like all other types of porcelain - can reduce the surface hardness by 1 Mohs. This hardness of the glaze makes the Alumina Porcelain resistant to all kinds of mechanical loads, such as those created when used with cutlery and ordinary cutlery. This resistance is called "ordinary cut resistance".
Lead & cadmium free
Our Alumina Porcelain is also constantly checked by independent research laboratories for the migration of lead and cadmium (EU regulations 84/500 / EEC and 2005/31 / EC) and for full conformity in accordance with the food commodities regulation. All articles have passed this test and are therefore intended for contact with food. Alumina porcelain is subject to the worldwide regulations regarding food contact.
The determination of the qualities of Alumina and High Alumina Porcelain in comparison to normal hard porcelain by determining the transparency. The following video is an excerpt from our "Determination" section from our merchandise knowledge.