SCT Sealing Primer

SCT Sealing Primer is a clear acrylic primer from Sealants & Coatings Technologies. It seals the substrate before a textured or elastomeric topcoat goes on, blocks moisture penetration, and stops tannic-acid bleed-through from staining the finish.

It is not optional on masonry work. The manufacturer requires it on all cementitious surfaces before Stucco Recoat 80/20 Textured Coating, eF-Coat Elastomeric Foundation Coating, or SCT Flexible Joint Compound.

Substrates

• Cementitious surfaces, existing stucco and masonry
• Structural insulated panels (SIPs) and foam form blocks
• OSB and urethane foam sheathing
• Aged wood
• Interior or exterior

How to apply

• Brush, roller or airless sprayer. No dilution needed.
• Apply one wet coat. Saturation is not required unless the surface is unusually porous or roughly textured.
• Wipe or brush out all runs and puddles. Do not let it build up — excess primer creates too thick a bond line under the topcoat.
• Milky white when wet, clear when dry.

Sequence matters

On most substrates, seal joints, windows and other penetrations before priming. On cementitious surfaces it is the reverse: the primer goes on first, before any caulking or SCT Flexible Joint Compound.

Surface preparation

The surface must be clean, dry and structurally sound, and free of loose, crumbly or chalky material, oil-based finishes, dust, oil, solvents, fungi and mildew. Clean by sandblasting, pressure washing or wire brushing.

Specifications

Good to know

• Odorless when dry. Salt spray stable per ASTM G-53.
• Do not apply if subfreezing temperatures are expected within 48 hours, and avoid rain. In hot weather, work the shaded side of the building.
• Do not let it freeze in storage. Store between 40°F and 90°F.
• Clean up with soap and water. Dried brushes need lacquer thinner.
• Contains petroleum distillates. Read the safety data sheet before use.