st21

Spray June 2016

bonanza if only the high-priced, heavy-duty can could be replaced with a lighter, less costly one. Research groups were established by the Crown Cork & Seal Co. (North Philadelphia, PA) and the Continental Can Company, Inc. (CCC) (Chicago, IL) to do just that. When their job was done, in 1947, the heavy-duty cans quickly passed into history. They are almost impossible to find today in antique shops, estate auctions and other outlets. The first “lightweight” aerosol cans were developed almost simultaneously in 1947 by small groups headed by Albert M. Glessner (Crown) and Harry E. Peterson (CCC). The Crown can was the “12 ounce Spra-tainer,” a strengthened version of the beer can they used for international customers. It was two-piece, with a body/ dome shell and concave bottom. The CCC can was a stronger version of the company’s 12-ounce, three-piece beer can, having a 2% tin and 98% lead soldered side seamed body, and two concave ends. In both cases an aerosol valve was soldered into a small hole in the center of the top. The composition of that solder is controversial, but it was probably a fusible alloy on the order of 40% bismuth, 40% lead and 20% tin, which melts at 232°F (111°C). The early valves contained brass bodies and stems but the buna and neoprene stem gaskets and some dip-tubes were adversely affected by excessive heat. These concerns vanished rather quickly in late 1952 when Crown introduced its nominal “one-inch” valve, followed quickly by CCC with a far more attractive top or dome, also carrying a nominal “one-inch” hole, sometimes called a plug. The black art of crimping the “one-inch” mounting cup of the new valve hermetically to the can bead or curl became the new challenge, since metric crimping accuracy and the vicissitudes of the poured-in Dewy & Almy neoprene cup gaskets sometimes led to crimp leakage. Modern Aerosol Cans Aerosol cans are regulated by the Dept. of Transportation (DOT) in several ways. They are limited to 1.000 liter (1.057 quart) capacity and to a diameter of 3" (76.2mm), although rare exceptions have been made. The so called “non-specification” cans must not be filled with compositions having a pressure over 140 psi-g (9.65 bars) at 130°F (54.4°C). They must not deform at this pressure and must not burst below 210 psi-g (14.5 bars). The “DOT Specification 2P” cans must not be filled with products having a pressure above 160 psi-g (11.03 bars) at 130°F (54.4°C). They must not deform at this pressure, or burst below 240 psi-g (16.6 bar.) Finally, the “DOT Specification 2Q” cans are permitted to hold formulas with pressures not to exceed 180 psig (12.41 bars) at 139°F (54.4°C). They must not deform at this pressure or burst below 270 psi-g. The DOT has other requirements involving the use of metal thicknesses of 0.007" (0.178mm) minimum for DOT-2P and 0.008" (0.203mm) minimum for DOT-2Q. They issue renewable Special Permits on a quid pro quo basis. For instance, a can may be shipped interstate with a content whose pressure is (say) 200 psi-g (13.8 bars) at 130°F (54.4°C), provided the dispenser is a steel or tinplate “safety can” with a fitment designed to open and relieve the pressure if it becomes excessive. Record-keeping, testing, printing the DOT-2P or DOT-2Q logo and other responsibilities fall to the can-makers. They recognize that metal thickness can vary up to about +/-5% for steel and tinplate and even a bit more for some aluminum cans. Therefore, they produce DOT-2P and DOT-2Q cans that are typically at least 10% greater in plate thickness than the regulatory minimum. Similarly, for buckle and burst these cans will withstand pressures at least 10% greater than required. Aluminum “Monobloc” cans easily comply with the thickness minimums. In the case of an exemplar 45mm x 190mm DOT-2P aluminum can, buckle began at 238 psi-g (16.3 bars) and rupture took place at 395 psi-g (27.2 bars). In the case of modern three-piece tinplate cans, there are six diameters, measured across the exterior of the body. They are: 112 (45mm), 115 (49mm), 202 (52mm), 205 (57mm), 211 (65mm) and 214 (70mm). The 112 is the smallest diameter can, able to be produced using standard bodymakers without generating excessive scrap. Some twenty years earlier, U.S. can manufacturers also produced 207.5 and 300 diameter cans, but they were discontinued for commercial and aesthetic reasons. Numbers such as 112 hark back to the old and former British system for describing the diameters of tinplate cans, such as those used to contain foods and beverages, long before aerosol cans arrived on the scene. In the case of 112, the can diameter is one and 12/16 inches and for 214 it is two and 14/16 inches. Can body heights are similarly described. The tallest European and Japanese tinplate aerosol cans are the 211 x 1113, where the body height is 11 and 13/16 inches. Their capacity is 989 ± 10mL—very close to the international 1.000 liter limit. The capacity of all aerosol cans is published as a “brim full” figure, usually in mL. This can be slightly misleading since, when the nominal “one-inch” cup is crimped on, the true capacity becomes about 3mL less than the brim full or overflow figure. Can capacity can be an important factor in determining safe product fills, as well as complying with the DOT Tariff CFR Part 173.306(a)(i), applicable to aerosols of up to four fluid ounce (118.3mL) capacity. Three can producers also make two-piece steel or tinplate aerosol cans. The oldest is the ITW Sexton Can Co.; it offers 202 (52mm), 211 (65mm) and 300 (76mm) steel, unlined cans in four heights for each diameter. They range from 118 to 775mL in overflow capacity. Another is DS Containers (Batavia, IL). It produces laminated An ad for the Crown Spra-Tainer Japanese 207.5 x 1111 plain tinplate hair spray can holding 750mL of product. June 2016 SPRAY 21


Spray June 2016
To see the actual publication please follow the link above