Sansin Stain Blocking Primer

High-Performance Primer for Wood Stain Discoloration Control

Sansin Stain Blocking Primer is a water-borne primer designed to prevent wood extractives, tannins, and resin bleed-through from discoloring topcoat finishes. Ideal for use under light-colored or solid-hide coatings, this primer provides strong adhesion, excellent breathability, and advanced resistance to staining agents. It’s an essential step when finishing wood surfaces prone to yellowing or bleed-through—especially on knots, cedar, redwood, and exotic woods.

What Makes Sansin Stain Blocking Primer Unique?

Unlike traditional oil-based stain blockers, Sansin’s formula is low-VOC, breathable, and easy to clean up with water. It adheres exceptionally well to wood surfaces and forms a tough yet flexible base layer that seals in tannins and resin. When paired with compatible Sansin topcoats—especially the SDF and Purity lines—it ensures a smooth, even finish that stays true to color without unsightly staining or blotching.

Key Benefits

• Excellent stain-blocking for tannins, knots, and sapwood
• Strong adhesion to wood and engineered substrates
• Compatible with water-borne topcoats including Sansin SDF and Classic systems
• Allows wood to breathe — non-film forming
• Fast-drying and low VOC
• Easy application and clean-up with soap and water

Where to Use

• Wood siding (especially cedar and redwood)
• Trim, soffits, fascia, and paneling
• Knotted pine and spruce
• Log homes where color consistency is critical
• Interior or exterior surfaces prior to topcoat stain or paint

Application Notes

Surface Preparation Requirements

• Clean surface of dirt, oils, or contaminants
• Sand smooth surfaces to ensure adhesion
• For best results, clean with Sansin Multi-Wash and allow to dry thoroughly
• Ensure moisture content is below 18%

Application

• Apply with brush, spray, or roller
• Stir well before and during application — do not shake
• Do not apply in direct sunlight or on hot surfaces
• Apply in temperatures above 10°C (50°F)
• Topcoat with Sansin water-borne finishes within 2–3 days

Coverage

Surface Type	Estimated Coverage per U.S. Gallon
Rough or porous wood	200–250 sq. ft.
Smooth surfaces	300–350 sq. ft.

Maintenance Required

Sansin Stain Blocking Primer is not a finish coat and must be topcoated. For long-term performance, always use compatible Sansin topcoats and follow recoat schedules specific to the finish system. Spot repairs can be made by sanding and recoating affected areas.

Frequently Asked Questions

What surfaces benefit most from a stain-blocking primer?

Knotted or resin-rich woods like pine, spruce, cedar, and redwood that often show bleed-through or discoloration under light stains or paints.

Can I use this under oil-based stains?

No. It is designed for use under Sansin’s water-borne coatings like SDF, Classic, and Purity systems.

Is it breathable?

Yes. It allows moisture vapor to escape while blocking bleed-through and tannins.

Will it affect wood color or grain visibility?

It may slightly tone the surface, but it is designed to maintain wood character while blocking discoloration. It’s not a solid hide coating.

Does it prevent all types of bleed-through?

It significantly reduces the risk of bleed-through from tannins, extractives, and knots when properly applied.

What if I apply the topcoat too late?

For best adhesion and performance, topcoat within 2–3 days. If delayed longer, clean and lightly sand before recoating.

How many coats are needed?

One coat is typically sufficient. Heavier bleed-through areas may benefit from a second coat.

Can I use it indoors?

Yes. It’s low-VOC and suitable for interior surfaces where discoloration is a concern.

Is it tintable?

No. It is not a color coat—it’s a clear to slightly opaque primer used beneath finishing products.

How should I store it?

Keep from freezing. Store sealed in a cool, dry location out of direct sunlight.

Downloads

• 📎Sansin Stain Blocking Primer Product Data Sheet (PDF)
• 📎Sansin Stain Blocking Primer Safety Data Sheet (PDF)