What temperature can I apply Liquid Rubber Waterproof Sealant? Liquid Rubber Waterproof Sealant should be applied above 5°C (41°F). Avoid hot, direct sunlight applications. Related articles How should I prepare the surface before applying Waterproof Sealant? What should I use to clean up? Can I build my final membrane all at once? What if I see blisters? The black surface turns brown when wet? Comments 0 comments Please sign in to leave a comment.