Quote:


That is my recipe. I don't remember the exact ratio of Penetrol to the Brightside but the ratio is on the Penetrol can. The zhan cup is the little plastic paint viscosity measuring cup that came with a piece-of-crap electric sprayer that I bought years ago. I found that a reading of 25 seconds for the cup to empty to be pretty close to perfect for my painting style. The good part with the zhan cup method is that the 25 seconds to empty viscosity level seemed to work just fine on warmer days and also on cooler days as the viscosity is temp dependent.



Aussie Driver:
The Zahn cup is a great idea. Since it was first mentioned on the forum here, I've done some research and found out that Zahn cups come in different sizes. Any idea what size or number cup you have???

Here's some of the info I found:
http://www.gardco.com/pages/viscosity/zhancups/ez.html

http://www.paintcenter.org/rj/Dec02m.cfm
If you intend to measure the viscosity of organic coatings, you will want to purchase a Zahn #2 and/or a Zahn #3 viscosity cup. The Zahn #2 cup is intended for coatings that have a relatively low viscosity, generally in the range of 18 - 35 seconds. For high solids coatings you might find that the Zahn #2 cup is too insensitive and that viscosity measurements go well above 35 seconds. I have measured coatings with a Zahn #2 measurement well in excess of 1 minute. For these higher viscosity coatings I suggest that you use a Zahn #3 cup so that with the larger orifice at the bottom of the cup, you can bring the measurements back down to 18 - 35 seconds. The most important consideration in selecting between Zahn #2 and Zahn #3 is that you get a clear break in the paint stream as it effluxes from the cup. If you find that as the cup empties the paint stream stops and starts, and stops and starts again, then you are probably using a cup for which the orifice is too small, and you should probably go to the next higher cup number.

Someone might recommend that you use a Ford #4 cup instead of a Zahn cup. Before you purchase one or the other, here are some differences. The Ford #4 viscosity cup has a very much larger orifice than the Zahn cups, and for the most part they are used in paint or coating laboratories where more accurate measurements are required. They are well suited to laboratories, but probably are less convenient for paint production shops. If you have a mixing table in your paint shop and you want accurate viscosity measurements, then the Ford #4 cup is fine. But if your operation is not so critical of viscosity and if the painters are likely to forget to properly clean the cup after using it, the Zahn cups are probably your preferred choice because they are less expensive.