What the Heck is a Ford #6 and # 8 Viscosity Cup?

[David Ruhland]

I am "testing" a waterborne Poly Topcoat and the TDS says "Viscosity using Ford Cup #6 40 +/- 5" I have googled a conversion chart for a ford #6 to #4 and found nothing. I cant even find a place to buy a number 6 cup lol.

I did thin the product 10 percent and am able to spray beautifully with my 1.8 Fujispray, but i am just curious if there is a conversion chart?

Thanks..

[Gary Petersen]

I don't believe you'll find a perfect conversion chart as different sized cups work for different viscosity ranges. While there is some overlap between successive cup sizes, there isn't much. Moreso when skipping a size between cups. Having said that, searching for viscosity cup conversion chart turns up many hits that might be helpful to you.

[Rob Luter]

I've always used Zahn cups. But this will tell you all you want to know about Ford cups: https://en.wikipedia.org/wiki/Ford_viscosity_cup

[David Ruhland]

Thanks... That clears things up :-)