+1 (954) 946-9454

30 Seconds in a Zahn Cup

What Does it Really Mean? 

Fifty-eight years ago it meant just what it says. Today these words can still be found in many technical specification sheets and literature, but today the phrase can be misleading, erroneous and meaningless because many makers have copied this cup and their efflux time in seconds can greatly differ from one make cup to another make cup, from one production run to another, as well as from one cup to another in the same lot. Differences of over 50% have been recorded.

Some original specifications were based on the early G.E. Zahn Cups. Unfortunately, such cups were not calibrated which often resulted in variations of efflux time in seconds from cup to cup. We make two calibrated Zahn type cups that do differ in efflux time in seconds in order to meet both past and present specification requirements. These two cups are the GARDCO S90/Zahn Signature Dip Cups and GARDCO EZ Zahn (ASTM) Dip Cups.

GARDCO S90/Zahn Signature Dip Cups are designed to meet the earlier specifications. Be sure to update your specification sheets and literature to include the type of Zahn cup (EZ or S90/Zahn Signature), the cup # and the efflux time in seconds. Only use CALIBRATED cups with a GARDCO (Paul N. Gardner Co., Inc.) nameplate.


  1. You can convert S90/Zahn Signature Dip Cup readings to ASTM D 4212 readings using the EZ to S90/Zahn Signature Seconds Conversion Charts by GARDCO. This will allow you to maintain the records you have established with your S90/Zahn Signature Dip Cups, and also enable you to invert to ASTM D 4212 readings if necessary, even though the cup Constants and Formulas for the S90/Zahn Signature Dip Cups differ from ASTM Specification D 4212. Sets of graphs with flow curves detailing these differences are available on request.
  2. GARDCO Cups give reliable, credible, accurate readings.
  3. EZ Cups are calibrated to within 3% tolerance.
  4. S90/Zahn Signature Dip Cups are calibrated within 5% tolerance.
  5. All GARDCO Cups can be calibrated and furnished with a set of Calibration Charts to convert seconds efflux time to viscosity in Centistokes.
  6. A wall size "Viscosity Cup Equivalent Chart" allows you to convert efflux times in seconds to viscosity in Centistokes for all 45 cups made and calibrated by Gardco.
  7. All GARDCO cups are calibrated with standard liquids traceable to the National Institute of Standards and Technology.
  8. Both GARDCO EZ & GARDCO S90/Zahn Signature dip cups qualify for Calibration Certification under ANSI/NCSL Z540-1 as applicable.
  9. Oils used to standardize GARDCO Cups are produced in accordance with ISO 9002.
  10. Take advantage of the 20% trade-in allowance on your old Zahn Type cup for purchase of a new EZ cup. (Dealers Excluded).

What You Get When Buying a Gardco Viscosity Cup...

  • Complete description of cup use, accessories, & prices.
  • Set of 5 conversion charts, efflux time versus Centistokes viscosity.
  • Calibration Oil Temperature/Viscosity charts for all 5 cups.
  • Questions and answers about viscosity cups.
  • Instructions for use.
  • How to calibrate your GARDCO viscosity cup.
  • Information on viscosity cup calibration liquids and prices.
  • ANSI/NCSL Z540-1 Tracebility Statement
  • Set of five charts to convert S90/Zahn Signature efflux time to EZ efflux time. (Sent only on request).

Watch out, for all those so called “Zahn-Type” Viscosity Cups out there!

Your products as well as your reputation are too valuable to use just any old type of “Zahn cup” just because it carries the name “Zahn-type” cup. There are many different producers of “Zahn-type” cups out there and all of them are different from one another, and everytime you buy another cup of the same make the odds are it could be a little bit different from the ones you have.

Why Are All These Cups Out There Different?

  1. Most of the cups out there cannot meet ASTM and ISC Specification’s requirements. Gardco EZ Cups meet and exceed ASTM D- 4212 and ASTM D-816. Calibration Oils used to standardize EZ Cups meet ISO-9002.
  2. None of them offer a Drain Time Warranty of 3% based on standard oils of certified viscosity. Gardco Calibrated EZ Cups do.
  3. Most of the cups out there are not certified liquid calibrated cups. Gardco EZ Cups Are Calibrated.
  4. None of the cups out there have printed fundamental viscosity information about their use along with technical information regarding cup calibration, etc. Gardco EZ Cups provide complete details.
  5. None of the cups out there have copyrighted conversion charts to convert tenths of seconds into centistoke viscosity. Gardco EZ Cups come with free Conversion Charts.
  6. Some of the cups out there have orifices drilled off-center. Gardco EZ Cups have perfect orifices.
  7. Some of the cups out there have oval, out of round orifices. Gardco EZ orifices are perfectly round.
  8. Some of the cups out there are so shabby they don’t even come with instructions for use. Complete Gardco EZ Cup instructions are furnished with each cup. A Conversion Chart is also included.
  9. Some of the cups out there are so poorly made they don’t come with an identity nameplate. Gardco EZ Cup nameplates are very informative.
  10. None of the cups out there have copyrighted Conversion Charts and formulas for them so that tenths of seconds efflux time can be converted immediately into basic centistoke viscosity. Gardco Calibrated EZ Cups are furnished with formulas and copyrighted Conversion Charts.
  11. None of the cups out there have a copyrighted wall size Viscosity Equivalent Chart that enables conversion between cups number 1 through 5 or between other types of Viscosity cups. Gardco has such a chart which includes all 46 Efflux Cups produced by the Paul N. Gardner Company. Ask for literature. This chart is only valid for Calibrated Gardco Cups.
  12. None of the cups out there can be documented in the way Gardco cups are documented. Gardco (Paul Gardner Company) Cups are documented.
  13. None of the other cups out there can be traded-in for a new cup with a 20% trade-in allowance. Gardco gives you a 20% discount when you trade an old Zahn type cup for a new Calibrated EZ Viscosity Cup.
  14. Most of the cups out there are so unreliable that their results can sometimes vary from one production run to another. Gardco EZ Cups' guaranteed accuracy is always 3% year-in year-out when they leave our plant.
  15. Some of the cups out there are made by foreign and domestic firms that admit they have no guarantee of accuracy and even state that they cannot promise one cup will be like another. Buying an uncalibrated cup is like buying a yardstick without measurements. Calibrated EZ Cups give you a standard basis of reference. EZ Cups' 3% accuracy is guaranteed year-in, year-out, when they leave our plant.
  16. None of the cups out there can be furnished with a Calibration Certificate that qualifies under MIL STD 45662A. Gardco EZ Cups qualify for certification under Mil Std 45662A. Ask for Certification price.
  17. Most cups out there are not furnished with Certified Calibration Oils when requested. Gardco “G” Series Certified Calibration Oils that meet ISO can be furnished for use with EZ cups. Ask for information.
  18. Most of the cups out there are not backed up by technical assistance on viscosity matters when needed by phone or fax. Our Physicist is always available to assist our customers in the use of Viscosity Cups.
  19. No other cup offers conversion information between two types of cups. Gardco does. We can furnish individual and/or sets of Conversion Charts that give conversion in seconds of readings on all five Gardco Zahn Signature Cups to all five Gardco EZ Cups. Ask for information. We also have a wall size Viscosity Equivalent Chart for use with all 35 Gardco Efflux-Type Viscosity Cups. It includes Zahn Signature Cups, EZ Cups, Ford Dip Cups, Standard Ford Cups, Fisher Cups, ISO Cups, ISO Dip Cups and Din Cups.
  20. Some of those cups out there are a bit lower in price than an EZ cup. You really get what you pay for. For a few dollars more an EZ Cup will give you accurate, reliable service for many years if treated properly. Buy an accurate, Calibrated EZ Cup with the Reliable Gardco name.

Trade-In those old uncalibrated cups ready for the junkyard!

  1. Remember Calibrated EZ cups won’t give you the same efflux time readings as uncalibrated cups that you might have been using. EZ Cups meet specifications and with an EZ cup you can determine what the viscosity of your material is by using the Conversion Chart furnished with each cup that converts seconds efflux time to centistokes viscosity. This gives you a standard basis of reference.
  2. Remember we cannot accept return of viscosity cups. Once they are immersed in coatings, paint, ink or other materials, they cannot be restored to their original appearance. Be sure which size cup you wish to use before you make a purchase. Maybe we can be of help.
Join our Email List. subscribe