Dow Corning 121 Two Part Structural Silicone

DOWSIL™ 121 Structural Glazing Sealant is a two-part silicone formulation explicitly designed for use in structural glazing applications in field and factory applications. The material is supplied in a two-part cartridge in which the catalyst is a smooth, white paste and the base is tinted either black or grey. Once catalysed, the material cures into a medium modulus, flexible silicone rubber that is flexible for use in structural and weather seal applications. It can be used in deep, narrow joints to obtain a complete cure. DOWSIL™ 121 Structural Glazing Sealant will fully cure in deep sections within 24 hours and generally achieves full adhesion within 48 hours. However, full cure time depends on joint design, substrate type, temperature and humidity.

Dow Corning 121 Two Part Structural Silicone


Approved for structural and weather seal applications1 according to EOTA ETAG 002, ETA 17/0405

  • High level of mechanical properties
  • Structural capability
  • Odorless and non-corrosive cure
  • Excellent stability through wide temperature range: -50°C to 150°C
  • Stable viscosity for base and catalyst, no heating required
  • The cured product exhibits excellent weathering characteristics and a high resistance to ultra-violet radiation, ozone, heat and humidity.
  • Primer less adhesion to alodine and anodised aluminum2
  • Adhesion to DOWSIL™ structural sealants for reglazing applications
  • Adhesion and structural strength achieved in 24–48 hours
  • Meets ASTM C719 Class 25 (G, A, O)
  • Meets ASTM C1184 Structural Sealant Specification

Technical Data Sheet

Dow Corning 121 Application Guide

Dow Corning 121 Application Guide

Available Colours


The Dow Chemical Company / Dow Corning Video

Additional Products

Dow Corning 1200 OS Primer 

Dow Corning 1200 OS Primer is used to improve adhesion and accelerate adhesion build-up of silicone sealants to various substrates. This moisture curing primer is supplied as a dilute solution of reactive materials in low viscosity siloxane.

Dow Corning Structural Spacer Tape

Dow Corning® Spacer Tape for Structural Glazing is specially formulated for many outdoor mounting and joining the application, including spacer tape for structural glazing. It has especially excellent bonding strength and high holding power on LSE (low surface energy) materials such as PVDF coated panel without primer in most cases.