Foster® 40-30C Protective Coating

1 of 184 products in this brand
Foster® 40-30C Protective Coating is a low-odor, fast-setting, water-based surfacing material intended for field or shop application to faced or unfaced fiberglass duct liner, fiberglass duct board insulation, or galvanized surfaces. Its low viscosity makes it suitable for application with a wide range of spray equipment currently available on the market.

Product Type: Coating, Waterborne Sealant

Application Area: Duct Liner

Application Method: Brush, Roller, Spray

Compatible Substrates & Surfaces: Fiberglass

Features: Fast Setting, Fire-Resistant, Fungus Resistant, Highly Flexible, Low Odor, Low Viscosity, Mildew Resistant, Moisture Resistant, Mold Resistance, Stain Resistant, Water-based

Message our experts with questions
Robert Blackstone avatar

Robert Blackstone

Global Leader - Inside Sales

Please reach out to me with any questions, I am happy to assist you in finding the right product or learning more about our storefront

Enhanced TDS

Identification & Functionality

Features & Benefits

Labeling Claims
Product Highlights
  • Foster® 40-30C resists mold, fungus, discoloration from mildew and stains by mold. 40-30C has been formulated with an EPA-registered fungicide to resist mildew growth.
  • Its extremely high level of resistance enhances the longevity of the material.
  • Foster® 40-30C dries to form an effective, air erosion preventive, surfacing material sealing and reinforcing the surface of new or aged duct liner insulation materials.
  • Foster® 40-30C is non-flammable when wet and extremely fire-resistive when dry.
  • When tested on both faced and unfaced fiberglass duct liner insulation, Foster® 40-30 produced flame and smoke ratings below the 25/50 NFPA 90A and 90B requirements.
  • The dry film stays flexible and moisture resistant. It will not cause flash rusting on metal surfaces.

Applications & Uses

Application Area
Application Method
Compatible Substrates & Surfaces
Preparation and Application Information

Material Preparation

  • Do Not Thin. 
  • Keep container closed when not in use.

Surface Preparation

  • Apply only to surfaces free of all loose dirt, grease, mold or other materials that may interfere with the adhesion of the coating to the substrate.
  • HVAC systems: Always follow industry accepted cleaning procedures. Lined air ducts must be lightly vacuumed to remove all mold, dust and loose particles, being careful not to tear or loosen the liner. Galvanized surfaces need to be vacuumed or washed clean of all accumulated mold, dust and loose particles. Ensure that all interior surfaces are thoroughly dry before applying Foster® 40-30C. See metal surface preparations for primer requirements.
  • Masonry, brick, plaster and cement-based surfaces: On mold-infested surfaces, aggressively scrape the surface, then wire brush to produce a firm, sound substrate. Clean the intended surface of any materials that may interfere with the adhesion of the coating and allow to dry completely before proceeding. Prime all unpainted brick, plaster and cement-based surfaces with a masonry sealer or primer if dusty. A block filler may be used to patch and smooth porous surfaces.
  • Painted surfaces: Wire brush painted surfaces, removing all flaking, loose or chalking material. Sand all glossy surfaces (alkyl, oil, epoxy-based coatings, etc.) to roughen entire area. Alternately, a primer may be applied to glossy surfaces to improve adhesion; adequate adhesion must be confirmed prior to completing application. Clean the intended surface of any materials that may interfere with the adhesion of the coating and allow to dry completely before proceeding.
  • Metal surfaces: Remove any dust, grease, oil or materials. Abrade all surfaces to remove all surface rust. Clean the intended surface of any materials that may interfere with the adhesion of the coating and allow to dry completely before proceeding. All rusted, metal surfaces must be primed before application of Foster® 40-30C. Foster® 40-30C may be applied directly onto cleaned, unrusted, galvanized surfaces.
  • Unpainted wood and drywall: Remove all dirt, grease, oil, loose mold or mildew or other materials. Remove all loose substrate materials, unnatural protrusions, splintered materials, etc. to a sound surface. In wall cavities or unexposed surfaces, Foster® 40-30C may be applied directly without the need for primer. On exposed surfaces where staining or discoloration of the coating would be objectionable, prime with a stain blocking primer.


  • Always ensure adequate ventilation.
  • HVAC systems must be under negative air pressure during and after application to allow for exhausting of odors and rapid drying of the coating.
  • Apply Foster® 40-30C to all surfaces by brush or airless spray at the following wet coverage rates (rates are minimum required and are subject to the nature of the material being coated):
    • Galvanized Metal: 0.75 gal./100 sq. ft. (0.31 l/m2 )
    • New Duct Liner: 1.0 gal./100 sq. ft. (0.41 l/m2 )
    • Old Eroded Duct Liner: 1.5 gal./100 sq. ft. (0.61 l/m2 )
    • Wood, Drywall, OSB: 0.33 gal./100 sq. ft. (0.14 l/m2 )
  • Unsealed, rough or low-density surfaces may require more material to attain required surface sealing.
  • Brushing will require two heavy coats applied at 90° to each other.
  • Under normal circumstances, a spray application can be completed in one coat, but for extremely porous or irregular surfaces, a second coat may be required.
  • Ensure that the finished surface is smooth and well-sealed.
  • For airless spray application, use an electric 2800 psi minimum pump with a 0.015 – 0.025 fluid tip.
  • Clean brushes and equipment with warm water before product dries.


  • Continue to circulate fresh, dry air throughout the area during the application and for as long after the application as is possible.
  • Exhaust circulated air outside the building or occupied space. If air must be exhausted inside the building, circulate air through an air scrubbing filtration system with odor absorbing medium such as a charcoal medium.
  • This circulation and filtration helps to reduce the dry time of the coating and reduce latex-type odors that could possibly migrate from the application area.
  • Be sure exhausted air is odorless before venting into occupied spaces.


  • Normal cleaning procedures must be maintained in HVAC systems to remove accumulated airborne particles.
  • Where accessible, the coating may be washed down periodically to remove any accumulation of materials with water and a mild detergent.
  • If coating becomes damaged, clean surface and re-apply coating.


Physical Form
Typical Properties
ValueUnitsTest Method / Conditions
Average Weight11.0lbs.ASTM D1475
Average Non-Volatile (by Weight)51.0% ASTM D2369
Average Non-Volatile (by Volume)35.0% ASTM D2369
Coverage Range (Old Eroded Duct Liner)1.5gal./100 sq. ft-
Coverage Range (Galvanized Metal)0.75gal./100 sq. ft-
Coverage Range (New Duct Liner)1.0gal./100 sq. ft-
Drying Time (Set to Touch)6.0HoursASTM D1640
Drying Time (Dry Through)24.0HoursASTM D1640
Wet Flammability100.0°C-
Application Properties
ValueUnitsTest Method / Conditions
Service Temperature Limits (at coated surface)-50 to 180°F
Flame Characteristics
ValueUnitsTest Method / Conditions
Flame Spread ¹10ASTM E84
Smoke Developed ¹5ASTM E84

¹ - Tested at a coverage rate of 150 sq. ft./gal. Applied to 1” (25 mm) faced duct liner. The flame spread may vary at different product thicknesses and/or when applied over other surfaces.

Regulatory & Compliance

Quality Standards

Storage & Handling

Shelf Life
12 months
Storage and Handling Conditions
  • Store between 40°F (4°C) and 100°F (38°C).
  • Protect from freezing. Apply between 50°F (10°C) and 100°F (38°C) with less than 70% RH air conditions maintained until dry.
  • Water-based products may corrode carbon steel spray equipment.
  • Corrosion resistant pumps and fittings are suggested.
  • Avoid direct application onto pressurized PVC or CPVC piping and wipe off or remove overspray. For interior use only. 
  • Do not dilute.
  • For professional use only.