Part II: Defining The Dye Ingress Operating Window

By Oliver Stauffer

As syringe-based products evolve toward higher viscosities and larger fill volumes, longstanding assumptions about dye ingress testing face growing mechanical constraints. Earlier analysis showed that the method relies on a delicate balance: pressure must be high enough to force fluid out through a micro-defect, yet remain stable long enough to draw dye back in without the plunger absorbing that differential. Part II advances this understanding by quantifying where that balance collapses. By calculating the maximum product viscosity at which dye ingress can still generate a detectable signal—given realistic boundaries for defect size, pressure, plunger behavior, and detection limits—this section highlights the method’s hard physical cutoffs.

Gain a clearer sense of when dye ingress can be trusted, and when viscosity and geometry place it beyond feasible use.