About us

The various aluminum hydroxides (ATH, hydrate) and aluminium oxides (alumina) manufactured by Silkem Hungary Ltd. are made from purchased wet aluminum hydroxide and precalcined alumina raw materials obtained by bauxite processing.


Aluminum hydroxides are manufactured and sold in four main product groups:

  • normal dried ATH
  • white dried ATH
  • ground ATH (coarse, medium and fine)
  • viscosity optimized ATH

In terms of use, the most important properties of aluminum hydroxides are:

  • non-toxic
  • soft (MOHS hardness: 2.5)
  • good dispersibility, miscibility
  • good fire and flame retardant effect (thermal decomposition above 200 °C)

Dry aluminum hydroxides are important raw materials in the following areas:

  • aluminum compounds
  • glass, frits, glazes
  • ceramics
  • refractory materials
  • chemical and cosmetic products
  • synthetic zeolites

Ground and viscosity optimized ATH is mainly used as an environmentally friendly flame retardant filler in the manufacture of the following products:

  • cable insulation
  • plastic composites (BMC, SMC)
  • thermoplastics
  • polyurethanes
  • epoxy resins
  • polyester resins
  • aqueous dispersions
  • paints
  • papers
  • adhesives

Our aluminum hydroxide products:

Dried hydrates:

  • Normal dry hydrate: Alolt 01
  • White dry hydrate: Alolt 1AF

Ground hydrates:

  • Coarse grinds: Alolt 21AF, Alolt 2AF
  • Medium grinds: Alolt 28AF, Alolt 8AF, Alolt 38AF
  • Fine grinds: Alolt 30AF, Alolt 50AF, Alolt 59AF

Viscosity optimized hydrates: Alolt 704, Alolt 710, Alolt 720, Alolt 720T


In accordance with market needs, we manufacture and sell a wide range of special (non-metallurgical) alumina and ground alumina types with medium and low sodium oxide content, controlled specific surface area, and different particle size distributions.

The most important characteristics of alumina in terms of use are:

  • non-toxic
  • high hardness (MOHS hardness: 9)
  • good abrasive and polishing effect
  • good heat and electrical insulation
  • high chemical resistance
  • fire resistance
  • good heat and heat shock resistance
  • good ceramic properties

Main applications of alumina and alumina grinds:

  • corundum
  • tabular alumina
  • glazes, fries
  • glasses
  • household ceramics
  • technical ceramics
  • support insulators
  • refractory materials
  • abrasive and polishing materials

Our alumina products:

Unground alumina:

  • Low calcined aluminas: Alo -EX30, Alo-EX31, Alo-EX32, Alo-EX325
  • Medium calcined aluminas: Alo-EX33
  • High calcined aluminas:
    • Alo-GB1-K, Alo-EX34 (medium Na2O content)
    • Alo-Ex35LS (low Na2O content)

Ground alumina:

  • Coarse grinds:
    • Alo-DN-10, Alo-DN-7P (medium Na2O content)
    • Alo-EL-7P (low Na2O content)
  • Medium grinds:
    • Alo-G4-4G, Alo-DN-4F, Alo-DN-4S (medium Na2O content)
    • Alo-EL-4F, Alo-El-4S (low Na2O content)
  • Fine grinds:
    • Alo-DN-3S, Alo-KN4FM (medium Na2O content)
    • Alo-EL-3S (low Na2O content)

Polishing alumina:

  • Low calcined aluminas: Alo-P90, Alo-P90-20, Alo-DF2, Alo-P90-06, Alo-P90-02
  • Medium calcined aluminas: Alo-P95, Alo-P95-08, Alo-P95-06, Alo-P95-01
  • High calcined aluminas: Alo-P54, Alo-DFM, Alo-P54-04

Reactive aluminas:

  • With medium Na2O content: Alo-DN-2S, Alo-DN-21, Alo-DN-23, Alo-KN-2S
  • Low Na2O content: Alo-EL-2S