A low modulus, one-component, versatile, general purpose, high performance silicone construction sealant for demanding caulking, glazing and industrial applications.
SIR-O-SIL 50™is a versatile, neutral cure, one component high performance low modulus silicone. SIR-O-SIL 50™ reacts with atmospheric moisture to produce a flexible silicone rubber. SIR-O-SIL 50™ is ideal for a wide variety of general purpose caulking, glazing and industrial applications. and provides high movement capability of +/- 50%. SIR-O-SIL 50™ has excellent weatherability and has exceptional shelf life that requires no special storage conditions.

Basic Uses

The low modulus profile and outstanding physical properties of SIR-O-SIL 50™ allow for sealing a wide variety of demanding applications:

  • Building, glazing and industrial sealing applications
  • Perimeter pointing around all types of frames, including PVC building products
  • Sealing construction joints in brickwork, concrete and stone subject to movement up to + or - 50%
  • Sealing between precast concrete panels
  • AMMA approved for a back bedding, glazing compound

Capable of taking extension, compression, transverse and longitudinal movement, SIR-O-SIL 50™ resists severe environmental conditions such as wind loading, wind driven rain, snow and sleet and is impervious to acid rain, ozone, ultraviolet light and extreme temperature variations. The tenacious adhesion of SIR-O-SIL 50™ provides long-term performance required for demanding weatherproofing applications. SIR-O-SIL 50™ is recommended for use on both new and renovation applications.


  • Non-corrosive curing mechanism
  • Excellent movement capabilities (+/-50%)
  • Excellent gunnability throughout a wide temperature range -35ºF to 160ºF (-37ºC to 71ºC).
  • Excellent unprimed adhesion to many common substrates
  • Long product life expectancy
  • Highly resistant to ultraviolet light, ozone, moisture and extreme temperature variations
  • Dry tools easily to a smooth, attractive finish
  • Good tear resistance
  • Rubberlike properties are maintained throughout product life
  • Service temperature range -65ºF to 300ºF (-54ºC to 149ºC)
  • Skins quickly
  • No special cold storage requirements are necessary

Typical Properties

As Supplied
Sag or Slump
Tack-Free Time at 77ºF (25ºC), 50% RH, minutes
Tooling Time, minutes
Specific Gravity at 77ºF (25ºC)
As Cured - After 7 days 77ºF (25ºC) and 50% RH
Durometer Hardness, Shore A, points
Ultimate Tensile Strength, PSI (MPa)
230 (1.9)
Tear Strength, PLI (kN/m)
25 (4.4)
Peel Strength, PLI (kN/m)
20 (3.5)
Movement Capability, percent
Weathering (10,000 hours in Quv. Weatherometer)
No change in color; remains elastomeric
Extrusion Rate, g/min
Please contact Siroflex® Inc. Greenville, SC prior to writing specifications on this product.

Limitations - Not for

  • Exterior below grade use.
  • Continuous water immersion.
  • Applications over tars, asphalt or materials that bleed oils, plasticizers or solvents.
  • Marble substrates.
  • Applications in airtight enclosures as the sealant requires atmospheric moisture to cure.
  • Horizontal traffic joints.


SIR-O-SIL 50™ is available in 10.1 fl. oz. (299 ml) cartridges, 12 cartridges per case/140 cases per skid. Bulk packaging (5 and 55 gallon containers) is available by special request.


Clear and White

Application Standards

SIR-O-SIL 50™ Silicone Sealant meets or exceeds the test requirements of:

  • Federal Specification TT-S-0001543A (COM-NBS) Class A.
  • Federal Specification TT-S-00203C (COM-NBS) Type 11, Class A.
  • ASTM Specification: C-920 Type S, Grade NS, Class 25, Use T, NT, M, G, A: and GSA (C.I.D.) No. AA-1556 Type S, Grade NS, Class 25, Use T, NT, M, G, A.

SIR-O-SIL 50™ meets the performance requirements of AAMA 803.3-92, Type II and is approved by AAMA

Storage Life

Product Shelf life is 12 months under normal storage conditions of 80ºF (27ºC) or less. No special cold temperature storage provisions are required.


Immediately available from both Siroflex® Inc. distributors and distribution centers strategically located throughout the U.S.


Cost information is available from your local Siroflex® Inc. distributor or by calling our Customer Service Department 1.800.359.6398.

Bead Configuration for General Purpose Sealing

SIR-O-SIL 50™ silicone sealant should have a ratio of approximately twice the joint width to sealant depth. The sealant depth should be not less than 3/16" (4.8mm, minimum) and not greater than 1/2" (12.7 mm, minimum). See the table below.


Joint Width-to-Depth Recommendations for General Purpose Sealing









B. Depth








C.Lineal ft./gal








Joint Backing - Bond Breaker

Joint backing should be used to control the recommended joint depth and prevent 3-sided adhesion. Joint backing may be open cell polyurethane foam or closed cell polyethylene. Joint backing must be thoroughly dry. Where joint design or depth will prevent the use of joint backing, an approved adhesive backed polyethylene bond breaker tape must be installed to prevent 3-sided adhesion. Do not install more joint backing or bond breaker tape than can be caulked in one day.


SIR-O-SIL 50™ can easily be applied with conventional hand or air-powered caulking equipment. The sealant should be applied in a continuous operation with adequate pressure to fill the joint to the proper width and depth. (Do not overfill the joint.)


Dry tool the sealant with light pressure immediately after application to ensure positive and complete contact of the sealant to the joint interfaces.


Should masking be required, it is recommended the masking tape be removed immediately after tooling, before the sealant skins. If necessary, the sealant can be installed below freezing provided the surfaces are clean, dry and frost-free. We recommend, however, for best conditions and performance, that the sealant be applied above 40ºF (4ºC).

Cure Rate

7-14 days


Cleaning of equipment and tools can be accomplished with solvents such as xylol, while sealant is uncured.

Notice to Purchaser

Siroflex® Inc.warrants its products to conform to Siroflex® Inc. published specifications. The user shall determine the suitability of the product to their particular application. the foregoing warranty is in lieu of all other warranties expressed or implied, including those of the merchantability or fitness for any purpose not expressly set forth herein. Manufacturer’s and seller’s liability for damage hereunder shall not exceed the purchase value of the goods used. IN NO EVENT SHALL MANUFACTURER OR SELLER BE RESPONSIBLE FOR INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF OR IN CONNECTION WITH THE USE OF THIS PRODUCT BY BUYER, BUYER’S USER, OR ANY OTHER PERSON. Notification of claim must be sent in writing to Siroflex® Inc. The notice should contain a statement as to how the product failed to meet our warranty, the proof of purchase and the amount of refund claimed.

For more information, refer to the SIR-O-SIL 50™ SDS.