Keramicalia makes a range of cellular insulation materials based mainly on Hollofill tiny ceramic bubbles. These can also be made into a self-spreading insulation powder called Keratherm 1

Kerinduct 2 is a dry-spiking spinel forming induction furnace lining.

C.O. Spray is powder for mixing with water and spray repairing of coke oven jambs.

We stock various Industrial Mineral and Fillers for our on use and they are available for sale.


I get many enquires for alumina (Aluminium oxide) but there are a huge variety of grades varying from R5/kg to R56/kg.

Some varieties are:

Fused aluminas: They have been melted at 2000°C. They are solid and impervious.

Brown fused alumina: Brown, made from bauxite.

White fused alumina: Clear to white.

Fused chrome alumina: Dark ruby and emerald.

Pink fused alumina: Contains a small amount of chrome oxide.

Heat treated brown fused alumina: Blue grey

Tabular aluminas: R40/kg. 99.5% pure, white, mainly used in refractories. bright white, mainly used in slight porosity makes it bright white.

Polishing alumina: R56/kg has zero% coarse particles.

Catalyst alumina: Highly porous particles, as balls, “vermicelli” or powder.  New or used.

Pressing alumina: Spray dried powder for making abrasion resistant tiles. Very fine -5 micron.

Cell grade alumina: Raw material for aluminium manufacture.  From R6/kg for contaminated.

Volatilized alumina: Sub micron particles from boiled alumina.

Splinter alumina: Crushed wear resistant tiles.

Natural corundum.

Dross: The waste from aluminium production. Contains metal, nitrates and many impurities. Porous.

Grindings: Waste from abrasion manufacture.

Grog: Crushed refractory bricks

Balls: A wide variety of sizes and qualities.

Alumina fibre: High temperature insulation.

Bubble alumina: Hollow alumina balls.

Keraline: Woven alumina textile

Keratab: Powders: add water and pour into moulds to make refractory shapes.

Slip: Powder. Add water and pour into Plaster of Paris moulds. Fire to 1250°C to get hard shapes.

We stock all of these in small quantities.

Most of these come in a wide range of sizes. The main property is hardness, 9 on the Moh scale, just below diamond at 10. We also stock silicon carbide, 9,5 on the Moh scale in 42 different sizes.

C.O. Spray

C.O. Spray is a coke oven repair material. It is sprayed on in a similar fashion to hot gunning, but is a fine material. It is a heat setting alumino-silicate material.

Grading: 100% -2.8mm 90% -1.0mm

Chemical analysis:

Al2 O3 40.2%
Fe2 O3 0.70%
SiO2 51.8%
TiO2 0.09%
CaO 0.09%
MgO 0.28%
K2 O 0.88%
Na2 O5 1.92%
L.O.I. 2.74%

Pumpable: at +25% water addition.

Packaging: 20Kg plastic bags.

Shelf life: 4 years

Development no. 13907

Keratherm 1

Keratherm is an insulation cover composed of hollow glass spheres, less than «mm in diameter. It looks like light grey powder but is very free-flowing. It contains no carbon. Keratherm has a bulk density of 0.4g/cm³ and a specific gravity of 0.77g/cm³. Keratherm melts at around 1250ºC, but the bubbles do not pop, and the insulation properties are retained well past the melting point. The coefficient of thermal conductivity is 0,09W/mk. Consequently a layer of Keratherm remains cool on top for a very long time. The use of Keratherm reduces sculling. Keratherm virtually eliminates radiant heat from the surface of a vessel, allowing operators to approach it closely without protection, making sampling and temperature measurement comfortable. Keratherm prevents gas pickup from the atmosphere.

Packaging: 7.5Kg polyethylene bags.

Typical chemical analysis:

Al2 O3 37.9%
FeSiO2 47.5%
TiO2 1.06%
CaO 1.22%
MgO 0.94%
MnO 0.02%
K2O 1.5%
Na2O 0.48%
P2O5 0.94%


Applications: Ladle cover Tundish cover Ingot cover Skimmer bay cover


Hollofill is composed of hollow glass spheres, less than 0.5mm in diameter. It looks like light grey powder but is very free-flowing. Hollofill has a bulk density of 0.4g/cm³ and a specific gravity of 0.77g/cm³. This makes it the ideal lightweight filler. The hollow spheres are strong enough to withstand processing and mixing, and are chemically inert. Hollofill melts at around 1250ºC. The coefficient of thermal conductivity is 0.09W/mk. Hollofill has a volume filling capacity of 52%. Because of the free-flowing characteristic of the spheres, it can be used as a filler at very close to its saturation point. In a resin with a density of 1g/cm³, Hollofill can be added at 100% by volume, ie. 770g/Kg. The resultant composite density will be 0.885. Very few fillers are available which will reduce the density of resins. Even fewer fillers are available which will have virtually no detrimental effects on the flow properties of composites at a 50% volume addition. To sum it up, the benefits of Hollofill in resins and related products are as follows: Reduced cost. Reduced weight. Improved insulation. Improved fire resistance.

Packaging: 7.5Kg thick polyethylene bags.

Typical chemical analysis:

Al2 O3 37.9%
Fe2 O3 1.89%
SiO2 47.5%
TiO2 1.06%
CaO 1.22%
MgO 0.94%
MnO 0.02%
K2 O 1.5%
Na2 O 0.48%
P2 O5 0.94%

Bubble Alumina

Hollow balls of aluminium oxide. Used for thermal insulation between 1200oC and 1900oC.

Particle size: 1 to 2 mm is kept in stock, other sizes can be ordered.

Bulk density: 0.6kg / litre.

Composition: Pure alpha alumina

Al2 03 99 to 99.5%
Na2 O 0.18%
SiO2 0.1 to 0.7%
Fe2 O2 0.02%
CaO +MgO 0.02%

Particle shape: Near spherical, allows good packing and easy flow; it can be poured into place and it can be drained out of a lining through a hole.

Melting point: Approx. 1990 C.

Hardness: 9 on the Moh scale

Handling: Bubble alumina is totally inert and harmless.

Kerinduct 2

Description: A spinel forming alumina induction furnace lining. The aggregate is fused chrome alumina and the fines are high purity sintered and reactive aluminas and 12% dead burned seawater magnesia. There is no frit addition. Sintering is by spinel forming reaction which gives expansion and a tight sealed hot face, with powder behind it to prevent crack propagation.

Maximum service temperature: 1750ºC.

Density: Hand rammed density is around 2.9g/cm³.

Chemical analysis:

Total Aggregate Alumina fines
Al2O3 80% 87% 99.7%
Fe2O3 1.2% 2.0% 0.02%
Cr O 6% 10%
SiO2 0.2% 0.2% 0.04%
CaO 1.4% 2% 0.04%
MgO 12.0%
Na2 O 0.06% 0.3%
K2 O 0.6% 1%
P2 O5 0%


Sintering: 12 hours on low power, then 2 hours at 1680 – 1700ºC

Packaging: 25kg plastic bags

Shelf life: 6 months

Development no. 21943

Claimer: The above information had better be correct, since Dave Onderstall rests his reputation on it.

Kerinduct 2 Comparison

Below is a comparative analysis of Kerinduct 2 and other induction furnace ramming materials, taken from their data sheets. Note that it has the lowest silica content.

Chemical Analysis:

Kerinduct 2 1 2 3 4 5 6 7 8
Al₂0₃ 80% 83-85 85.5-88 90.6 83-84 88.0 84.4 88 87.3
Fe₂0₃ 1.2% 1 0.5 0.4 0.7 0.1 0.2 0.1
Cr₂0₃ 6% 0 0
Si0₂ 0.2% 9.5-11 0.3-0.8 3.7 0.5 0.6 0.8 0.6 0.35
CaO 1.4% 0.1 0.2 0.2 0.2
MgO 14.9% 10.5-12.5 0.1 14.5-15.5 10.0 14.2 10 10.75
Na₂0 0.06% 0.5 0.2 0.2
K₂0 0.6%
P₂O₅ 0 2.4-3
Other 0.7 1.1 0.7 0.95
Max. serv. T° 1700° 1700° 1750° 1800° 1700° 1815° 1750° 1815°
Density 2.9 2.97 2.97 3.14 2.8-2.9 3.04 2.93


1.  SIR Fe 84P

2. SIR Fe 85V

3. Veroram 95P

4. Capital D585

5. Dri-vibe 683A

6. Kingscrete 85

*Note: The chrome oxide is in the fused grain, not a green chromic oxide addition.

7. Induval 1010/2B

Kerinduct 2 Installation

Principle: A carefully graded powder is compacted as dense as possible with NO BINDER. On heating, the magnesia and alumina sinter to form the mineral spinel, and this expands and makes the lining tight. The cool part next to the coil remains powder, so that CRANKS CANNOT PENETRATE IT.

Compaction: The powder is not rammed, stamped or vibrated, it is “spiked”. Dry spiking is done with a sharp pointed tool, which may have 3 or more spikes, typically 75mm long. The spikes push the material sideways more than down, and compaction progresses slowly from the bottom of the layer, and the spike penetrates less. The top 20mm does not become compacted. It gets compacted after the next layer is added. Dry spiking is a skilled job, which cannot be learned from reading instructions. It should be learned by working with an experienced team. If one small area is neglected, a leak to the coil can occur.

Procedure: Place about 150mm layer of powder in the furnace. Spike it until the tools stop 20 to 30mm from the surface. This will take 6 men about half an hour. Add the next layer of 75mm and continue, up to about 30mm ABOVE the BOTTOM of the former level. Now scrape off the loose material on top, to the level of the former. Place the former in and start spiking the sidewalls. When the top is reached, dampen the powder with water and STAMP not spike, it down.

Cover with a capping material such as Keracap or Kerapatch.

Preheating: The former needs to be about 6mm mild steel.

Place a “button” of solid steel inside the former, about half the weight of the furnace capacity.

Start the preheat slowly; about 10% power for the first hour, 20% power for the second hour, 30% power for the third hour etc.

Add scrap to fill the furnace once molten.

After 10 hours, at full power, the furnace should be at around 1650°C.

Soak for about half an hour at 1700°C.

Industrial Mineral and Fillers

Alumina: (alumina oxide) aggregates, bubble, sintered, reactive, calcined splinter chrome alumina, white fused, brown fused, tabular, catalyst, Polishing. Aluminium Hydroxide
Aluminium Hydroxide Gel
Aluminum: powder and granular
Barites (Barium sulphate)
Cab o sil
Calcium aluminate
Caustic magnesia
Chrome oxide
Clays, Ball clay, Kaolinite, Fireclay, bentonite, pyrophyllite
Cobalt oxide
Cobalt oxalate
Foundary Sand
Fumed Silica
Fused alumina
Fused chrome alumina
Fused silica
Iron Powder
Paper pulp
Plaster of Paris
Precipitated Silica
Silica Fume
Silicon carbide
Zinc Powder