Nozzle Operation and Technique (Dry-Mix)
Nozzle technique controls quality more than any other single factor in dry-mix placement. Hold the nozzle perpendicular to the surface, at a consistent distance (commonly about 3 to 5 feet, adjusted for air pressure and output), and move in steady, overlapping passes. The stream should be cohesive, with minimal dust and low rebound. Watch the material: a proper mix holds together, sticks without sagging, and compacts on impact.
Water adjustment is continuous. Judge by appearance: too dry shows dust and dark, unconsolidated patches; too wet shows sagging, glistening, and slumping. Build up in uniform layers, working from lower areas upward where appropriate, and avoid letting material accumulate and then be blown into place. Keep the nozzle moving; dwelling in one spot over-wets and over-builds. Encapsulate reinforcement and fill corners by directing the stream at an angle that avoids shadowing behind rebar.
Traps: holding the nozzle too close or too far; angling the stream so rebound is trapped; adding water after placement instead of at the nozzle; spraying over previously placed material that has started to set; ignoring shadowed areas behind obstructions.
Worked example / rule of thumb: if you see dust and dark pockets, increase water slightly and confirm the stream is cohesive; if you see sagging, reduce water. Keep a consistent perpendicular distance and overlap each pass by about half the stream width to avoid seams and cold joints.