| The Breakroom > The Water Cooler |
| Viscosity - a question with pur'Poise' ? |
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| picclock:
Using a clear airline water drain 'cup' i marked upper and lower levels with a felt tip, and clamped it in a retort stand above a plastic 1 pint beer 'glass' to catch the fluid. I filled it with water and waited until the top mark was reached to start my stopwatch. The time to the second mark was 32 secs. Water has a viscosity around 0.89 (or 1) depending on the internet site. Timed again for consistency and spot on. Same test with paraffin (Kerosene) , viscosity 1.64, time 32 secs. Clearly things are not what they seem. Last desperate try with Isopropyl Alcohol, time 32 secs. Obviously the universe gods are tricksters and viscosity is just a myth !!! :bang: OK, I think I'm stumped on this, clearly there are things going on that I have no hope of understanding. If anyone does understands whats going on here please enlighten me - but for now I'm going to partake of a cold one to ease my addled mind. Best Regards picclock |
| waggle:
Liquid printing ink is affected quite noticeably by small changes in viscocity, so we had to measure the viscocity frequently, accurately and repeatable. The way we did this was as has been described in previous replies but with a calibrated cup. http://cdn.c.photoshelter.com/img-get/I0000gOr2CB9d3pE/s/860/860/Fphoto-67711210B-6RM.jpg It is just a cup with a hole in the bottom, but very accurately made. the cup is dipped into the liquid and at the point it is lifted out a stopwatch is started and at the point that the stream breaks up the watch is stopped. We used to aim for around 21 - 22 seconds which was around the consistency of single cream. The cup needs to be held vertical so that the fluid drains out cleanly, hence the shape of the handle, so if can be just held up on one finger. If you are just looking to compare the relative viscocities of different fluids then you could just make something similar. Start off with a small hole in the bottom and check the fluid that appears to be thinnest. Enlarge the hole if necessary to achieve an emptying time of between 20 and 30 seconds. Any shorter and the results may be unreliable but if the hole is too small your arm will start to ache before the cup is empty! Waggle |
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