The Accurate Way to Determine Ink Viscosity
You may very well be asking yourself right now, "What the heck is a Zahn Cup?" No, it's not something that you use to sip herbal tea when visiting the Dalai Lama in Tibet. It is the most commonly used device for determining viscosity in liquids. Without getting into a complicated (and impossible to understand) definition, in everyday terms (and for fluids only), viscosity is "thickness". Thus, water is "thin" having a lower viscosity, while molasses is "thick" having a higher viscosity. Viscosity describes a fluid's internal resistance to flow. The Zahn Dip Cups are most commonly used to determine the viscosity of flexo and gravure inks in the printing industry, with a #2 Zahn Cup or a #3 Zahn Cup being most widely used.
Using the Zahn Cup
A Zahn cup is a viscosity measurement device originally developed for use in the paint industry. It is a stainless steel cup with a tiny hole drilled in the center of the bottom of the cup. There is also a long handle attached to the sides. There are five cup specifications, labeled Zahn cup #x, where x is the number from one through five. Use large number cup sizes when viscosity is high, use low number cup sizes when viscosity is low. To determine the viscosity of a liquid, the cup is dipped and completely filled with the substance. After lifting the cup out of the substance the user measures the time until the liquid streaming out of it first stops flowing. This is the corresponding "efflux time". A conversion table relating efflux time in seconds (to the nearest tenth of a second) to viscosity in centistokes (the viscosity unit of measurement) is furnished with each Zahn EZ™ Cup.
Features of the Zahn EZ Dip Cup
There are several types of Zahn Cups (and Zahn-type cups) in common usage – the Zahn EZ Dip Cup, the S90/Zahn Signature Dip Cup, the Mini-Ford Dip Cup and several others. We have chosen to offer the Zahn EZ Dip Cup Series for several reasons:
- 3% guaranteed tolerance complies with and exceeds ASTM D4212
- The EZ Cup formula for each cup of the series matches the applicable ASTM formula in D 4212 at the recommended calibration level
- EZ Cup calibration is traceable to the National Institute of Standards and Technology, an important feature to shops striving for ISO Certification
- The EZ Cup is not matched by any other cup of its type, either with respect to the advantages listed above, in highest quality of workmanship or in continuing quality control procedures
- All stainless steel cup and handle
- The finest, most reliable, calibrated & documented cup on the market
The following table provides specifications of the various cups:
||Seconds Efflux Time
||Zahn EZ #1
||Zahn EZ #2
||Zahn EZ #3
||Zahn EZ #4
||Zahn EZ #5
A Zahn Cup is no different than any other precision quality control instrument. It needs to be calibrated from time-to-time, based upon its frequency of usage. The standard oils used for calibration are available from Lithco on a special order basis. Refer to the chart above when inquiring about calibration oils for your specific Zahn Cup.Certification certificates available: Must be ordered when the cup is ordered. Price $200.00.
Timing the Flow
As mentioned above, it is necessary to time the liquid flowing from the cup, accurate to a tenth of a second. For this purpose, We now offer a digital stopwatch, part # MIS-SW.
- Models: MIS-ZAHN1, MIS-ZCOG10, MIS-ZAHN2, MIS-ZCOG60, MIS-ZAHN3, MIS-ZCOG200, MIS-ZAHN4, MIS-ZCOG200, MIS-ZAHN5, MIS-ZCOG350, MIS-PU-G201, MIS-PU-G260, MIS-VI-201901, MIS-LA-2029060, MIS-CTTH16100860/C, MIS-CTTH02226/C, MIS-SW, MIS-AX725BKC & MIS-AX705