Waterproof Coating Options

waterproofing kit from Dynamic Systems
Waterproofing Kits, available through DSI, contain everything required to waterproof one 16"x18"x2" cushion. Additional tubes of silicone may be ordered depending on cushion size.

Laminar cushions with and without silicone waterproof coating
Laminar cushions with and without silicone waterproof coating.

Dynamic Systems provides waterproof coating materials, waterproof slipcovers, and waterproof fabric by the yard for SunMate, Pudgee, and Laminar cushions, and FIPS inserts.

Cushions may be ordered with a factory-applied waterproof coating for an additional charge.

DIY Waterproofing with Silicone

The silicone coating provides an elastic, waterproof layer which is safe for skin contact, resistant to odors and soiling, and won’t detract from the cushion’s support capabilities.

  • One tube of silicone will coat a 16"x18"x2" cushion.
  • The silicone may be applied directly to the cushion or to a fabric that is at least 50% cotton/polyester glued to the cushion surface, as on a FIPS insert.
  • The silicone sealant provides a high-friction surface.
  • Velcro® will not adhere to silicone. If applying Velcro® strips, first adhere a piece of fabric to the moist silicone. When the silicone is dry, glue the Velcro® to the fabric.
  • After waterproofing the cushion, cut a 1/16" slit at each corner to allow air to escape and circulate. Without these small cuts, air bubbles may form beneath the coating causing the silicone to separate from the cushion.

NOTE: Dow Corning 732 RTV silicone and GE Silicone II are two brands most often used to waterproof our cushions. GE Silicone II is available in white or clear and produces fewer fumes than the Dow brand. The two brands are not compatible and should not be used together.

Preparation

Apply the silicone in a well-ventilated area. The Dow Corning 732 RTV silicone sealant releases acetic acid fumes while curing. Wear latex gloves, and cover the work area with polyethylene plastic. Be sure the cushion surface to be covered is dry and oil-free.

Application

Holding the spreader

  1. Place half of the silicone tube contents in a paper cup or on a paper plate. Add an oil-based pigment if color is desired. Stir with a tongue depressor stick until well-mixed.
  2. Apply the first coat: Scoop half of your prepared silicone onto the center of the cushion. To obtain good penetration and even distribution, hold the spreader vertically as you scrape the silicone across the surface of the cushion. (See top image, at right.) Coat the top of the cushion and half-way down each side.
  3. Apply the second coat. Scoop the rest of the silicone on the top of the cushion. Hold the spreader at a 45o angle so the second coat creates a complete seal and a smooth, even surface. (See bottom image, at right.)
  4. Let the cushion dry to the touch. It will take 30 to 60 minutes, depending upon the humidity.
  5. Turn the cushion over and repeat steps 1-4.
  6. Cut away 1/16" of silicone at each corner so the air can flow through the cushion. (Cuts do not need to be made in a FIPS insert due to the large surface area.)
  7. Dust the cushion lightly with cornstarch or similar powder to reduce friction and create a smoother surface.

For details on finishing a FIPS insert, refer to the FIPS Instruction Manual.