Brand: Oscar Acoustics
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Manufacturer: Oscar Acoustics

Oscar Seal - Intumescent Sealant 310ml

Intumescent Sealant & Intumescent Mastic | Oscar Acoustics
Oscar Seal - Intumescent Sealant 310ml
£ 2.98 ex. VAT / £3.58 inc. VAT

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25+ 25%

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Oscar Seal - intumescent mastic - 310ml

Oscar Seal intumescent acoustic mastic is a high density, flexible, paintable Halogen free acoustic mastic that provides up to a 4 hour fire barrier combined with excellent sound damping properties.

Our intumescent acoustic mastic is ideal for:

  • Sealing irregular or uneven gaps around service penetrations or soundproof ceilings

  • Can be used with our Oscar Iso-Mount space saving soundproofing system

  • Sealing fire protection boards and partitioning

  • Sealing around door casings and sills

Delivery of intumescent sealant

Order before 12pm Monday-Friday for next working day delivery.*
Next day delivery is subject to having no courier issues. Some remote areas of the UK can take longer.  Delivery prices apply to mainland United Kingdom only.  Please contact us before purchasing online to receive a quote for delivery costs and times outside of mainland United Kingdom.  Our offices are closed over the weekends & bank holidays.  

Intumescent mastic technical information

This acrylic intumescent acoustic sealant is a ready to use sealant that is ideal for sealing uneven or irregular gaps around service penetrations, sills, door casings also for sealing fire protection boards and partitioning.  Use to seal low movement construction joints where fire rating is required. Can be used to seal joints up to 35mm wide for excellent building acoustics

Test data & classification of intumescent mastic

Tested independently to current specification: BS EN 1366 Part 4
Also complies with previous test: BS 476 Parts 20
Classification: ISO 11600 – 12.5P
Acoustic intumescent sealant properties: Tested to BS EN ISO 140-3:1995
Test report Nos. 125-76, 77,79-81

How to use acoustic intumescent sealant

Surfaces to be sealed with acrylic intumescent acoustic sealant must be clean, dry and free from dust, dirt, frost, grease and other contamination. Cut both the cartridge tip and applicator nozzle to the required diameter and angle, screw nozzle onto cartridge.  Apply sealant with applicator gun ensuring good surface contact is achieved by forcing sealant into the joint to be sealed.  If necessary, tool within 5 minutes of application using a spatula dipped in soapy water, apply sufficient pressure to ensure good contact of the sealant against the joint surfaces.  Clean tools with water immediately after use.  Wash hands after use.

Storage of acoustic intemescent sealant

Store Oscar Seal intumescent acoustic sealant in a cool dry environment, product can be stored for at least 18 months from its production date in original unopened container, at temperatures between +2C and +30C.  Do not allow to freeze.

Coverage of acoustic intumescent sealant

One Cartridge of Oscar Seal acrylic intumescent acoustic sealant contains sufficient material to seal 4 metres of a 12mm x 6mm joint.

Intumescent mastic limitations

Oscar Seal acoustic sealant is not be used in applications subject to permanent water immersion.  It is always the user’s responsibility to determine suitability of use.  It is not recommended for use in areas subject to abrasion.

Intumescent mastic health & safety

Avoid contact with skin and eyes.  In case of contact with eyes, flush immediately with water and seek medical advice. Wear suitable protective clothing and gloves.  Keep out of reach of children.  Do not ingest.



PRODUCT       Oscar Intumescent Sealant


Oscar Intumescent Sealant is a halogen free, polymer emulsion based sealant that swells when subjected to temperatures in excess of 125oC and forms a char coat that restricts the passage of smoke and fire.  It is easily applied and dries to a flexible and smooth surfaced material which is readily over paintable.  It has excellent adhesion to a wide range of substrates and will not harden or crack with age.


Oscar Intumescent Sealant has been independently tested to the following assessments:

  • BS EN 1366-3: 2004 & BS EN 1366-4: 2006 Tested at Bodycote Warrington Fire, report No. 173658A achieving up to a 4 hour integrity and insulation rating for a range of linear and penetration seals.
  • an indicative fire test based on BS476 Part 20 at Warrington Fire Research and achieved up to a 4 hour fire rating (integrity) for a range of vertical and horizontal joints up to 35mm wide between various non-combustible construction materials.  A 1 hour fire rating (integrity) was achieved for a range of vertical joints up to 25mm wide between combustible materials (timber).
  • BS EN ISO 140-3. 1995 Measurement of Airborne Sound Insulation of Building elements.

 University of Salford reports 125-76;77 and 79.  The sealant maintained the integrity of a plasterboard partition wall with a Sound Reduction Index of 55dB    


Oscar Intumescent Sealant forms a fire and smoke seal in joints up to 35mm wide without slumping.  It is ideal for sealing joints in and around internal partitions, lap joints in fire-rated cladding and for sealing between fire doors and fire-rated walls.  It is recommended that a sealant depth of at least 8mm be applied.

If the sealant is to be overpainted, building regulations may require a fire resistant coating.


Oscar Intumescent Sealant is not suitable in joints where movement exceeds ± 7.5% of joint width, or in external joints.


Movement Accommodation:       ± 7.5% Conforms to ISO 11600 7.5P

Skinning Time:                            15 mins to 1 hour depending on conditions.

Cure time:                                   5 to 15 days for 15mm X 20mm bead.

Hardness Shore A:                     25 - 30

Temperature Resistance:            -20oC to +60oC (intermittent)

Paintability:                                 With most paints.

Application Temperature:             +5oC to 40oC

Cleaning:                                    Uncured sealant with water.

Shelf Life:                                   min. 18 months when stored in unopened containers as recommended.

Specific Gravity:                          1.60 – 1.64



To achieve a high quality joint, clean all surfaces, remove dust and ensure surfaces are dry.  Non porous surfaces should be degreased using a suitable degreasing agent.  Highly porous surfaces should be sealed with a suitable primer. Apply masking tape to each side of joint and gun sealant firmly into joint, smoothing off with a wetted spatula.  Masking tape should be removed within 10 minutes of application.


1 tube is sufficient to produce approx. 1m using a 20mm x 15mm bead.


Store in cool dry conditions.  PROTECT FROM FROST.


Oscar Intumescent Sealant presents no known health hazards when used as recommended.  Consult Health and Safety data sheet for further information.  As with all chemical product, care should be taken during use and storage to avoid contact with foodstuffs, skin, eyes and mouth.  If accidentally ingested, seek medical attention do not induce vomiting and give copious amounts of water to drink.  


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