Photograph Printer Paper
There are many types of photographic printer paper. For use with a paper patternator the higher quality, thicker paper is desired because of their ability to accurately visualize spray patterns with a minimum of droplet spread. The paper must have good color retention and a low spread factor. When photographic printer paper is used and cards are prepared from letter sized sheets, the cost of a 3” x 4” card is only 4.6 cents. These cards are not altered by humidity and can be keep indefinitely. Ordinary paper has high droplet spread due to wicking of the spray through the paper. This results in inflated numbers for the amount of spray deposition over the actual amount of spray.
Initially both Office Max and Staples store brands were tested and no discernible difference could be found. For testing on the patternator, the Office Max papers were chosen. Office Max glossy professional (10 mil thickness), semi-gloss professional (10 mil thickness) and matte professional (10 mil thickness) were selected. Other papers tested were Hewlett Packard HP premium matte (9 mil thickness) and HP everyday glossy (8 mil thickness).
Water Sensitive Paper
Water sensitive papers must be handled with care because they are sensitive to moisture in the air, on the plant and on the hands. Water vapor from the plants can also cause the paper to turn blue. Water proof gloves must be worn when handling water sensitive paper or moisture from your hand will start to initiate a color change. The cards, made by Syngenta, are fairly expensive. The cost of water sensitive paper is 96 cents per 2” x 3” card and they come in packets of 50 cards. Once the packet has been opened, all 50 cards are exposed to the air and color changes can begin to occur. When initially removed from their containers the cards are yellow but can quickly start to turn green due to high humidity. Wherever water hits the paper it changes immediately to a deep blue. After use the cards must placed in sealed plastic bags and scanned shortly thereafter to reduce the likelihood of further color change.
To visualize the spray pattern, a dye must be added to the spray tank. The use of food coloring as a dye has been suggested by Dr. Landers of Cornell. Red food coloring was selected for this project because of its availability and pricing. It also requires a lower concentration to give readily apparent droplets on paper. Three different red food colorings were tested and the Shank's and Butler's brands gave the highest saturation of color. Both brands are made by the same company and are available on the internet. Red food coloring at a concentration of 40ml/gallon of water was utilized in all tests.
Blue dyes are commonly used in the lawn care and turf industries as spray pattern indicators. These dyes are available from pesticide wholesalers and retailers. The blue dye, Terramark SPI, was used in the project. Only half the amount of blue turf indicator was required for good color intensity as compared to red food coloring. These turf indicators are designed to break down in sunlight after about two days. No discernible color change has been noted with the blue dye even months after spraying if the cards are stored properly in sealed plastic bags and not exposed to direct sunlight. The blue turf indicator was used at a concentration of 20ml/gallon of water.
Image Analysis Software
Results obtained from a paper patternator can be expressed numerically using image analysis software. A software program, NESareScan, was developed for this project. It was compared with DepositScan, a free program available from the USDA. DepositScan was initially developed to interpret spray droplets from boom sprayers on water sensitive paper and is available at the USDA Research Service. Commercial programs are also available.
NESareScan and DepositScan were used to determine droplet density, droplet size and percent coverage.