Sometimes we encounter confusion about white foam. What I am referring to specifically is hydrophilic foam. It seems that all hydrophilic foam is white, but not all white foam is hydrophilic. The word "hydrophilic" means that the foam attracts water. This is in contrast to black or green foam which is hydrophobic, meaning it does not soak up and retain water. Negative pressure wound therapy (NPWT) foam dressing kits use hydrophobic foam. The foam conducts the suction down to the wound bed, and allows water to pass through and into the suction dome and out to the canister. 

Consequently, white foam is used as an addition to, not in place of black foam included in a foam kit. Due to its higher tensile strength it is used to pack into undermined or tunneled areas of the wound bed. It can also be used to cover and protect exposed tendons or bones.