C1 - Proper stand-off distance
To achieve the best blast pattern and profile on a surface while maintaining productivity, the abrasive nozzle should be kept at an appropriate distance from the work surface.
Being too close to the surface will produce a narrow blast pattern. Hence, it will take longer to prepare the area.
Holding the nozzle too far from the surface can result in poorer cleaning and the required profile might not be obtained.
For garnet media, the stand-off distance is ideally 46cm (18in) (although this can depend on the type of nozzle used).
C2 - Blasting angle
The angle of blasting can affect the productivity depending on the original state of the surface.
In general, a 90 degree angle will cause the abrasive to rebound, leading to reduced performance. However, in extreme cases, such as heavily rusted or pitted surfaces, angles between 80 and 90 degrees may prove to be most effective.
Too narrow an angle could cause the abrasive to skim across the surface, resulting in reduced profile.
When removing old paint, 45 to 60 degrees is typically used and for general cleaning it is 60 to 70 degrees.
When blasting with garnet, the most effective angles tend to be between 55 and 70 degrees, depending on the nature of the substrate.