Aerial spray deposits are commonly assessed by collecting samples of either undyed spray on oil-sensitive dyed paper cards or dyed spray on undyed cards. Since the spread of oil-base spray drops changes disproportionately with drop size, the spots on the cards must be converted back to the original (spherical) drop sizes. This is accomplished by dividing the spot diameter as measured on the card by a suitable spread factor. A procedure is presented for determining this spread factor. Variation of the spread factor with drop size, sampling surface. and different sprays is discussed. The spread factor increases with increasing drop sizes regardless of the kind of assessment paper and spray. The rate of this increase depends primarily on the kind and source of spray materials used in the formulation. Therefore, for an accurate spray deposit assessment, the spread factor should be determined for a range of drop sizes for each different spray formulation.
Document Type: Research Article
Publication date: October 1, 1962
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