A new Technique for sampling and assessing aerial Spray Deposits.

Printflex paper cards have been found to be a satisfactory simple surface for collecting samples of aerial sprays. The spread factor for an oil solution of an insecticide on Printflex paper is not constant for the various droplet sizes. Spread factors for dyed and undyed solutions of DDT in oil, on dyed and undyed paper, range from 3 6 to 6.2 for corresponding stains produced by droplets in the range 60 to 600 microns A new rapid photographic method of quantitative assessment of the deposit on Printflex cards is described The method eliminates the use of film for the process by employing a high contrast light weight photographic paper. The process provides a permanent record of the stains, enlarged 3 5 ×, with a suitable calibration grid recorded on the print. The assessment can be carried out without any further optical aids. A statistical analysis of the accuracy of the assessment of deposits on the cards, using the photographic method, has established that density of deposit, number of droplets per uni...