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"Paint Viscosity Chart / Cross-reference of Ford cups to Zahn cups"



Current question:

November 22, 2021

Q. Sir, how did you find that formula and what is that 3.85 value in the formula?

Deshmukh Prasad sampatrao
Student - Pune
^


"Viscosity of Liquids"
by Viswanath, Ghosh, Prasad, Dutt, Rani
from Abe Books
or

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November 2021

A. Hi Deshmukh. That formula is from ASTM D1200 [affil. link to spec at Techstreet], and is only valid when the efflux time is between 20 and 100 seconds. It's an empirical formula for the best fit across that time range for the Ford #4 cup. The best fits for other cups use different multiplicands and subtrahends.

Luck & Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^




Closely related Q&A's, oldest first:

Ford Viscosity Cup #4 with Certificate


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Set of Zahn Cups #1-#5


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2003

Q. I am looking for a paint viscosity chart that will give me relative comparisons between a #2 EZ Zahn cup, a #3 EZ Zahn cup, and a #4 Ford cup, with the ideal temperature of the paint being 77 degrees. I have been unsuccessful in my attempts to locate a chart using the resources I have available to me. Any direction would be greatly appreciated.

Juliana Frush
aluminum extruder & paint shop - Girard, Ohio
^


2003

A. You should be able to obtain tables with the conversions from the company that sold you the cups. Typically the EZ series Zahn cups come with a blue booklet that has these tables in them.

David J. Wolf
David J. Wolf
Medina, Ohio ^



To minimize search efforts and to offer multiple viewpoints, we combined previously separate threads onto this page. Please forgive any resultant repetition, failures of chronological order, or what may look like readers disrespecting previous responses -- those other responses may not have been on the page at the time :-)



25811
2005

Q. Many times I find it difficult to convert various viscosity parameters mainly between, Ford cup, Din cup, Iwata cup etc. Can anyone help me to find out an conversion chart between various measuring cups of viscosity.

SUBIR SIL
- Shanghai, Shanghai and PRC
^


2005

A. Not very difficult, really. I just googled "viscosity conversion chart" and got 489,000 hits. The very first one on the list =>
has a comprehensive conversion chart available for free download at a click of the mouse button. No doubt there are many others among the 489,000.

Bill Reynolds
Bill Reynolds [dec.]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.

^



2005

Q. In Ford cup the viscosity of paints is measured in terms of seconds. What is conversion factor for this to convert it into centipoise?

Lokesh Dhimole
- Bhopal, India
^


2006

A. The chart below may help you.

Chart for Viscosity Conversion for Reference

     cps    Ford#B3    Ford#B4    Zahn#2    Zahn#3
            (sec.)     (sec.)     (sec.)    (sec.)
	 
     10                  5         16
     20      12         10         18
     30      19         14         20
     40      25         18         22
     50      29         22         24
     60      33         25         27
     80      41         31         34
    100      50         34         41         10
    120      62         41         49         14
    140                 45         58         16
    200                 58         80         23
    240                 65                    28

The comparison given is for reference purpose only.

Meghan Manjrekar
- Pune, India
^


Viscosity Tester


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2007

A. Try www.visco.co.za/downloads/ford-conversion-chart.pdf for Ford cup conversion chart - efflux seconds to Centistokes - then convert CPs = cSt X S.G.

lesley graham
- Durham, England
^


January 10, 2012

thumbsdown www.visco.co.za/downloads/ford-conversion-chart.pdf appears to be a dead link. Any recent links referring to the same problem of converting FC - 4 data to poise?

PC Sarkar
- Ranchi, Jharkhand, India
^


July 31, 2012

thumbs up signviscositycup.com/ViscosityCupConversionChart.pdf

Atul Mishra
- Anjar, Gujarat, India
^

----
Ed. note: That one is broken now as well, but both the table offered by Bill Reynolds and the one offered by Meghan Manjrekar give you that comparison.



September 22, 2008

Q. I want viscosity chart for different temperatures in B4 Cup.

Mohan Subramaniyam
paint industry - India
^


A. Hi, Mohan.

The B4 cup offers you an estimate of the absolute viscosity of a liquid in centistokes based on its efflux time. The viscosities of liquids decrease with increasing temperature. But regardless of whether you specify the viscosity in terms of centistokes or Ford #4 efflux time or anything else, I think you would need to specify exactly what liquid you are speaking of before anyone could offer a chart to show the relationship between its viscosity and its temperature because different materials react so differently to temperature (when honey is hot it runs almost like hot water; when it's cold it's very much thicker than cold water). Good luck.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^



February 6, 2009

Q. Dear Meghan,

Do you have conversion of 552.317 cst to Ford cup #4 - secs.

Regards,

Aniruddha Oak
- Bangalore, India
^



A. Hi, Aniruddha.

Meghan's posting was from 3 years ago so he might not be around to answer.

But I think the basic issue is that there are practical limits to such rough conversions. Using a cup with a huge hole to measure the viscosity of thin liquids that will drain in a flash would be like timing a 100 meter sprint with a sun dial; and using a cup with a tiny hole to measure the viscosity of very thick fluids would be like using a stop watch to time the lifespan of an elephant :-)

The viscosity which you are trying to measure is beyond the workable range of an F4 cup. According to the previously referenced chart at www.visco.co.za/downloads/ford-conversion-chart.pdf, it looks like the efflux time for an F5 cup would be about 48 seconds.

Luck & Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^



April 15, 2009

Q. I find that Two cups - #4 cups never give the same results. Can anyone explain to me the reasons? I can verify the volume of cup and the dia of orifice. Can you correlate these parameters to the disagreement of the cups? How do I say that a particular #4 cup is faulty and should be discarded?

A. Dear David and other friends,
Try www.viscosity.com registrationreqd
-- Viscosity conversion tables by Norcross Corporation. I think it has wide range of useful information.

Sushil Samvatsar
- Aurangabad, Maharashtra, India
^

----
Ed. note: Although you can buy "certified" Ford #4 cups I'm not sure that that quite answers Sushil's question. If anyone can help, please do.




August 31, 2009

Q. Sir We are using ford cup #4. Our material is viscous. We are checking its time to empty the cup in seconds. Please send us how to convert it in to centipoise.

With Regards

Manikantan Rajan
executive - Ambernath, Maharastra, India
^


August 31, 2009

? Hi, Manikantan. Can you clarify in what way Meghan Manjrekar's chart did not fully answer your question? Thanks!

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


September 1, 2009

Q. Dear sir,

Sorry Sir I can't get the answer to the question from the chart of Mr. Meghan. My question was when the seconds is more than 200 sec how the conversion table will help. Please send me the conversion formula from seconds to centipoise at room temperature.

Thanks

Manikantan Rajan [returning]
executive - Ambernath, Maharastra, India
^


Ford Viscosity Cup #5


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September 1, 2009

A. Hi again Manikantan. Method ASTM D1200 [affil. link to spec at Techstreet] covers viscosity measurement with the Ford Cup. Please also try to also get hold of the ASTM Gardner/Sward "Paint Testing Manual" [affil. link to book on Amazon] as it has an excellent chapter on the subject of viscosity and its measurement with the various cups and devices. It includes a chart by Euverard showing a conversion factor of 3.7 for the Ford #4 cup. That is,

centistokes = efflux time x 3.7

centipoise = centistokes x specific gravity

But as previously explained to Aniruddha, you're using the wrong cup. A Ford cup with efflux time "more than 200 seconds", is a meaningless way, way, off the chart extrapolation :-(
A carpenter doesn't drive tacks with a sledgehammer, nor landscape spikes with his tack hammer; he uses different hammers for different jobs. Nor is there a single cup that allows good measurement of all possible viscosities. I think the basic problem is that you are trying to measure a high viscosity liquid with the wrong cup for the job; the first step would probably be to get a cup which is designed for higher viscosity liquids than the #4 cup . . . like a #55 cup. Best of luck!

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


September 10, 2009

Q. Conversion of viscosity
We are using Dr Beck's varnish Elmotherm 97. Viscosity as per manufacturers specification is 300-400 mPa.s. We are using Ford #4 cup for checking the viscosity.of the varnish.
In how many seconds the cup should become empty. Please also specify the orifice of B4 cup. Please clarify.

V.K. Chebbi
Supplier of laminated stampings - bangalore.India
^


December 2, 2009

Q. How to measure the viscosity in #4 ford cup? Is there any calculation available? Please clarify.

siva balan
Quality Engineer - Chennai , Tamil nadu, india
^


December 3, 2009

A. Hi, Siva. In light of the previous answers and referenced charts & tables, I am not fully understanding wherein the difficulty lies. Can you please try to re-cast your question in terms of the answers already supplied? Sorry, I understand that the information supplied is deficient for your needs in some way, but I don't know not in what way :-) Thanks!

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


April 8, 2011

A. As per the ASTM D1200 [affil. link to spec at Techstreet], "Standard Test Method for Viscosity by Ford Viscosity Cup", the following formula is used to convert efflux time in seconds (unit s) to Kinematic viscosity (unit cSt.) for Ford Cup Number 4:

Kinematic Viscosity (cSt) = 3.85 (t - 4.49), where t is efflux time in seconds.

Please remember that this ASTM method (D1200) covers the determination of Newtonian or near-Newtonian liquid materials. For non-Newtonian, Method ASTM D2196 [affil. link to spec at Techstreet] should be used.

Dr. Danish Jamal
- Pune, India
^


June 25, 2011

Q. From where are you all getting the factor 3.7 please tell me for the problem of manikantan.

Amit Patil
student - Maharastra
^


June 2011

A. Hi, Amit. Unfortunately my copy of the book I quoted is out on loan so I can't double-check but, as I recall, "3.7" is simply an empirical factor that is reasonably close for a narrow range of efflux times. If you look at the previously referenced chart at www.visco.co.za/downloads/ford-conversion-chart.pdf, you will be able to see that the centistokes is reasonably close to 3.7 times the B4 efflux time in seconds.

The ASTM D1200 [affil. link to spec at Techstreet] formula quoted by Dr. Jamal is presumably a better fit.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


October 15, 2011

Q. Sir, I want the conversion of Ford cup B4 unit in second to poise.
So please tell me how can I convert this.

Pravin K.
student - Gujrat, India
^


March 3, 2013

Q. Can I measure viscosity 120-130 in #4 Ford cup?

Shah j.r.
- Vadodara, India
^


March 5, 2013

A. Hi Shah. Yes. But I can't tell whether there is something here which is specifically confusing you, or whether you haven't read the page :-) Please explain what it is about Meghan's chart that you are not following . . . then we will be able to clarify it. Thanks!

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^



Conversion of B4 cup to Zahn cup #2

July 30, 2013

Q. I would like to compare the results of my paint with other lab for NATA.
The other lab has used B4 cup using our paint and our lab has used Zahn cup #2 for viscosity testing.
Therefore I would like to see if my instrument is giving the correct reading with other lab.
Basically I am doing the Inter-laboratory testing.

So what is the relation or conversion factor from B4 cup to Zahn cup #2?

Dinesh Chandra
- Brisbane, Qld Australia
^


July 31, 2013

? Hi Dinesh. Why is Meghan's chart insufficient for you? Please detail the issue for me. I am trying to understand this continuous repetition of a question that I thought was already very clearly answered several times. Please clarify what happens when you look for your answer on that chart. Thanks!

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


August 4, 2013

Q. All I need is the conversion chart or any similar that would enable my Zahn cup is giving us the true reading as #4 cup.
The #4 cup measured from other lab is made of Brass.

Is B4 cup same as Ford B4 CUP?

The results are as follows :

Zahn cup#2         B4 cup
Sample B : 26s         22s
Sample A: 29s         34s
How would you explain the conversion?

Dinesh Chandra [returning]
- Brisbane, QLD Australia
^


July 2013

A. Hi Dinesh. As noted, Meghan Manjrekar has already posted the relationship between Zahn #2 Cup and Ford B4 cup on this page so you can compare your Zahn readings vs. the Ford B4 readings and decide if they are close enough. To me they don't seem to be close enough because for sample A the Zahn reading was lower that the Ford reading, which goes against the whole direction of the chart.

To my knowledge, the only B4 cup is the Ford B4 cup, but I think you can't resolve this unclear communication by asking a 3rd party what the party of the first part was thinking :-)    Good luck.

Regards,

Ted Mooney, finishing.com
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^



January 28, 2016

Q. Hello all,
As my project work I am designing an impeller for a mixing tank for solvent based paint having viscosity 100 to 140 sec (ford cup 4).
What will be equivalent viscosity in Cps?

Thank you

Ruchir Patel
- dortmund,NRW,Germany
^


January 2016

A. Hi Ruchir. Although I am not an expert on this stuff, I am confident from simply reading this page, and looking at the several conversion charts on it, that your problem is the same as previously explained to Aniruddha and then explained again to Manikantan, i.e., that you have a cup that is designed to measure a lower viscosity fluid, and you are trying to use it to determine the viscosity of a higher viscosity fluid.

You're not finding the conversion factor that you're looking for because extrapolation can lead to huge errors and they DON'T WANT YOU TO EXTRAPOLATE. The charts tell you the viscosity of fluids that drain in 5-60 seconds, probably most accurately when the drain time is in the 20-40 second range. So when you ask the viscosity of a fluid that takes 140 seconds to drain from a Ford B4, the chart writers and cup makers don't want you to hazard wild & unrepeatable extrapolated guesses … they want you to use a cup with a bigger hole :-)

Luck and Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^


March 2, 2016

A. Paint viscosity is not a simple subject. Most paints are deliberately formulated to have non Newtonian characteristics. i.e. they typically contain thixotropic agents which give non drip properties. The flow rate (viscosity) depends on the shear speed so that the paint goes on thin and does not immediately flow off again before the solvent evaporates.
Ford, Zahn and similar measures are simple devices for use in the paint shop to confirm that under a very limited set of conditions the paint is thinned to a degree suitable for spraying. They are only comparators.
If you need a more accurate assessment you could start with
http://www.brookfieldengineering.com/download/files/Paint_Viscosity_Temperature.pdf
Welcome to the world of Rheology.

geoff smith
Geoff Smith
Hampshire, England
^

----
Ed. note: That link is broken now as well. Google is for live searching; the page is for permanent reference. Please use google to search for the conversion charts you need.


May 31, 2017

A. From literature, I find that the kinematic viscosity (cSt) tapers off with increasing flow times in Ford cups or Zahn cups, above 40 - 60 secs flow times. So, it does not make much sense to measure flow times that exceed 60 secs, and try to correlate to cSt / cPs.

Mohan Das
Polymer Consultant - Bangalore, Karnataka, India
^



May 22, 2018

Q. Kindly clarify conversion unit for viscosity from cst to KU unit.

PURUSHOTHAMAN Devaraj
- Trichy,India
^


May 2018

A. Hi Purushothaman. There is a 2-step conversion process presented at https://www.gardco.com/stormer_krebsconv_PU-G271.pdf … first you convert Krebs Units to centipoise from a graph they offer you, then you convert centipoise to centistokes by dividing by the specific gravity (S.G.) of your liquid. You can work it in reverse by multiplying your centistoke value by the S.G. to obtain centipoise, then look on the graph for the corresponding Krebs Units value. As that page will warn you, and this page already warns you, such conversions are only accurate for newtonian and near-newtonian fluids (where shear force is directly proportional to speed) and within very limited ranges. Good luck.

Regards,

pic of Ted Mooney
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
^

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