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Expanded perlite is a white, ultra-lightweight aggregate ranging from a very fine powder to an aggregate with a particle size up to 6mm in size. It is inorganic, inert, neutral in pH, biologically stable and has no asbestos content. It has excellent thermal insulation properties over an extremely wide temperature range from cryogenics at minus 273oC (absolute zero) up to refractory applications at over 1000oC. It also has a highly adsorbent surface and a very low bulk density which makes it an ideal carrier or low cost filler for many compound formulations.



The source of the ore for the manufacture of perlite is a naturally occurring siliceous volcanic rock. This is quarried, crushed and screened into closely graded fractions. 



Perlite is converted into expanded perlite by heating it in a furnace. When quickly heated to above 870oC (1600oF) the crude rock pops in a manner similar to popcorn as the combined water vaporises and creates coutless tiny bubbles in the heat softened glassy particles. It is these tiny glass sealed bubbles which account for the light weight and excellent insulating properties of expanded perlite. 


Chemical Properties

The mineral is an aluminium silicate and under normal conditions is chemically inert. Typical composition of expanded perlite is:

Silicon (SiO2)


Aluminium (Al2O3)


Iron (Fe2O)


Sodium (Na2O)


Potassium (K2O)


Calcium plus Magnesium (CaO+MgO)





6.5 - 7.5

Organic Matter


Moisture Content (when packed)



Physical Properties

The density of the particles can be varied by changing the method of expansion. The actual specific gravity of the mineral fraction is between 2.2 and 2.4. The bulk density despends of the density of each particle and their grading. Consequently the bulk density ranges from 40 to 120 kg/m when poured and 50 to 150 kg/m when compacted.

Softening Point

890 - 1100oC

Fusion Point

1280 - 1350oC

Specific Heat


Refractive Index



Reaction to Fire

Perlite is classified for reaction to fire as Class A1 in Decision 96/603/EC, as amended by Decision 2000/605/EC.


There are ten grades of expanded perlite currently available:


Nominal Size (mm)

Loose Poured
Bulk Density (kg/m)

P05 Ultrafine

0.01 - 1.0

90 - 180

P3 Cryogenic

0.75 - 1.2

35 - 55 (LW)
80 - 90 (HD)

P6 Extra Fine

0.10 - 1.70

45 - 85

P10 Super Fine

0.15 - 2.0

80 - 100

P15 Medium

0.15 - 3.0

80 - 100

P25 Special

1.0 - 3.0

55 - 75

P35 Standard

1.0 - 5.0

 85 - 110

PCLG Chimney Lining Grade

1.0 - 5.0

85 - 110

P321 Through Grade

0.15 - 6.0

95 - 110

P40 Extra Coarse 3.0 - 6.0 85 - 105

P45 Super Coarse

1.0 - 6.0

95 - 110

Note: Nominal particle size indicates the 80% band i.e. up to 10% above of below the specified range.

Prices and Conditions of Sale

Prices are quoted on a volumetric basis, ex works plus haulage. All quotations give, orders placed. and materials supplied are subject to our Standard Conditions of Trading, a copy of which is available on request.



Expanded perlite is normally supplied in heavy duty printed plastic sacks holding a nominal 100 litres when packed. A range of alternative packaging and bulk bags from 50 litres to 1250 litres are available on special order.  



Expanded perlite can be collected from our production unit at Ellesmere Port or delivered direct anywhere in the UK. A full vehicle load is 750 bags. 

Free trial bags can be sent to any company in the UK in response to a written request indicating the type of application and potential usage if satisfactory. Technical information is also available for many applications and advice can be given on alternative bonding systems to make rigid shapes, etc.

Health and Safety

 Click to download a copy of the Material Safety Data Sheet.



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