EPS blanks must be sealed properly before laminating. Resins without micro-balloons added, will soak deep into EPS foam, making it difficult to properly wet out laminating cloths. This means you can use much more resin than is necessary. This creates a heavy board, trapped air and pinholes; and loses the advantage of a lighter blank.

Although there are other methods of sealing EPS blanks, sFoam™ recommends using the "aviation" method of sealing structural foam.

Mix one part (by volume) micro-balloons and one part (by volume) epoxy resin/hardener. Squeegee this mixture over each side in turn, be sure to use a minimal amount to make a dry coating (try making a final hard pass with the squeegee). Make a final hard pass over the stringer when you finish the sealing, to remove the sealer from the stringer.

Let side cure, repeat on other side.

Use a "cake frosting" consistency of epoxy/micro-balloons to fill in any pukas or dents left in the blank ( this can be done before the initial sealer is fully cured. )

When both sides have been done and cured, dampen a clean cloth with de - natured alcohol and wipe the blank. Then lightly sand the blank with 100-150 grit sandpaper and laminate.

Using the micro-balloon mixture keeps the epoxy from migrating too deep into the foam, yet insures a total epoxy-to-epoxy bond with the laminate and a strong bond to the foam.

Epoxy fill, sanding and finish coats offer the highest strength and better UV resistance, although some epoxy resins may require more work to sand.

Polyester resins can be used on top of epoxy laminations; as fill, sanding and finish coats, but just do not let these resins come in contact with raw EPS foam.