Powder blasting (abrasive jet machining) is a fast directional machining technique for brittle materials like silicon and glass. The cross-section of a powder blasted channel has a rounded V-shape. These inclined sidewalls are caused by the typical impact angle dependent removal rate for brittle materials. It has a negative influence on the channel depth and aspect ratio, and results in the blast lag: wide channels become deeper compared to smaller channels. Two approaches are studied in this paper that can influence this effect: using smaller powder particles and decreasing the particle jet impact angle (oblique blasting). Calculations and measurements show that the blast lag can be reduced for these two cases. However, oblique blasting requires additional equipment and results in low mask/target selectivity while the reduction in blast lag is relatively small. Powder blasting with smaller particles is much easier to perform and leads to straighter sidewalls and a large blast lag reduction. © 2002 Elsevier Science B.V. All rights reserved.