Home / Resources / How to compare viscosity measuring cups in seconds to centipoise
How to compare viscosity measuring cups in seconds to centipoise
A cup second is not a centipoise. Convert efflux time to centistokes, then multiply by specific gravity. The original PDF is the chart. Call 800-249-0337.
Preview · about 1 minute
Plant-floor overview. Unlock below for the full converter checklist.
The original PDF is a viscosity conversion chart: cup seconds (Zahn, Ford, Shell, and related cups), Gardner bubble, Stormer/graphic, and Saybolt Seconds Universal (SSU) against centipoise. Use the PDF for the grid. This page is how to read it without mixing units.
What a cup actually measures
Dip the cup, lift, and time until the stream breaks. That efflux time is kinematic viscosity (flow under gravity), usually as centistokes (cSt). Centipoise (cP) is dynamic viscosity. For a given liquid, cP is about cSt times specific gravity, at the temperature you measured.
Report cup results as seconds, cup number, and temperature, for example "22 s, Zahn #2, 77 F", then convert if you need cP for a spec.
Typical Zahn conversions (ASTM D4212)
v in centistokes, t in seconds. Stay inside the cup's drain-time window (often about 20-80 s) or the equation lies.
- Zahn #1: v = 1.1 (t - 29)
- Zahn #2: v = 3.5 (t - 14)
- Zahn #3: v = 11.7 (t - 7.5)
- Zahn #4: v = 14.8 (t - 5)
- Zahn #5: v = 23 t
Ford cups follow ASTM D1200 (Ford #4 is common on inks and low-viscosity coats). Shell cups are the same ASTM D4212 family as Zahn, with different orifices. Gardner bubble tubes (A-Z) and SSU sit on other columns of the same chart.
Do not mix cup brands without checking the chart. A "#4 second" on Ford is not a Zahn #4 second. Measure at the temperature in the TDS. Hot-melt viscosity is a Brookfield number at application temperature, not a cup second.
Related Cattie grades
- 8241 — Water-based acrylic PSA. A cup or Brookfield number on the TDS.
- 8250 — Masking-tape PSA.
- 8299 — Lower-viscosity PSA for foams, films, and foils.
- 8347 — Flexible water-based heat seal.
Call 800-249-0337 or email sales@cattieadhesives.com.
Longer plant training (5–10 min)
Coming soon — downloadable deep-dive for the floor.
General plant guidance only — not a substitute for your process, SDS/TDS, or line trials. Call 800-249-0337 to match a grade.