Patternator Testing - 2012
Droplet Size
The NESareScan computer program for interpreting spray cards determines the volume median diameter. This can be written as VMD or Dv0.5. The volume median diameter is the point where 50% of the volume is in larger droplets and 50% of the volume is in smaller droplets. Droplet size is measured in microns or micrometers (µm). Once the percent coverage reaches 20%, the droplet size becomes very difficult to measure. The measurement is the most accurate at a very low percent coverage. As the percent coverage increases the droplet size also increases with both the NESareScan and DepositScan programs.
Statistically some significant differences were found in the droplet size. The blue spray pattern indicator had significant differences between the water sensitive paper and the other papers used during the first test when analyzed using both NESareScan and DepositScan. Tukey's hsd test was run comparing the various papers with the blue dye. Only the samples taken close to ground were used for statistical analysis.
| Treatments | Mean (µm) | Tukey's hsd test | |
|---|---|---|---|
| gloss | 488 | a | treatments with different letters are significantly different |
| semi-gloss | 500.75 | a | |
| matte | 482.25 | a | |
| water sensitive paper | 349.25 | b | |
semi-gloss: 1% level of significance
| Treatments | Mean (µm) | Tukey's hsd test | |
|---|---|---|---|
| gloss | 497.5 | a | treatments with different letters are significantly different |
| semi-gloss | 507.25 | a | |
| matte | 479.0 | a | |
| water sensitive paper | 373.0 | b | |
No significant differences were found with the red food coloring and the various papers in the second, third or fourth tests at the same height with both NESareScan and DepositScan. In the second test only the cards at 1.5 feet were analyzed and for the third and fourth tests the cards at 1.0, 1.5 and 2.0 feet were analyzed. The droplet size does increase as the percentage coverage increases for both dyes and all papers. The same is true with both NESareScan and DepositScan.
| Treatment | Height of cards | ||
|---|---|---|---|
| 1.0 feet | 1.5 feet | 2.0 feet | |
| gloss | 344.5 µm | 407.25 µm | 511.75 µm |
| semi-gloss | 294.5 µm | 388.5 µm | 525.25 µm |
| matte | 286.0 µm | 352.25 µm | 420.25 µm |
| water sensitive | 301.5 µm | 311.25 µm | 397.75 µm |
| Treatment | Height of cards | ||
|---|---|---|---|
| 1.0 feet | 1.5 feet | 2.0 feet | |
| gloss | 1.45% | 5.33% | 13.43% |
| semi-gloss | 0.88% | 3.55% | 12.0% |
| matte | 0.85% | 3.03% | 8.58% |
| water sensitive | 0.95% | 2.4% | 9.73% |
This is a typical result that occurred in all the tests. The lowest percentage coverage cards should be the only ones used for determining droplet size.
The red food coloring had smaller droplet sizes than the blue turf indicator in the first and second tests but only the matte paper was significantly different when using the NESareScan data. No significant differences were found with the DepositScan program.
It is difficult to get accurate droplet size determinations with either program when using an air blast sprayer.