How to Stack
When the pulp is stacked away a space of at least an inch should be left between each can to allow the air to circulate and prevent stack burning. If this is not done, a pile of pulp may hold the heat for a week or ten days, and the pulp, particularly that on the inside, will become brown or even black, due to the long exposure to the heat. The quicker the pulp can be cooled, the more the bright red color of the tomato will be retained.
The height to which the pulp is stacked depends upon the heaviness of the plate of which the can is made, and also, of course, upon the weight the floor of the warehouse is able to stand. As a rule it is not wise to pack 5–gal. cans of 107–lb. plate over four high, and not over five high for cans of 135–lb. plate. Dry, sheltered storage should be provided for pulp, and it will be found to pay in the end. Exposure to the elements is very hard on the cans, and alternate freezing and thawing of the pulp is a great strain on the seams of the can. A comparison of the leaks and swells on pulp stored in shelter, and that stored in the open, will convince the packer that it pays to construct dry storage space.
Narrow aisleways should be provided for between the stacked pulp so that it can be frequently inspected for leaks and swells. By pulling out a leaker in time, several other cans are prevented from becoming leakers, as the leaking pulp from one can will run down on several others, and the pulp, in connection with the oxygen of the air, will eat through the tin plate, causing rust spots, and then pin holes. Frequent inspection of the pulp pile and pulling out cans when they are just beginning to leak or swell will save the packer a lot of money.
Cans should not be stacked on thin boards which will leave the surface of the can close to the ground, as the moisture of the ground will quickly rust the tin. It almost seems foolish to mention such a point, but much pulp is stacked this way and the entire bottom layer when turned up will be moldy and rusty on one side. The surface of the can should be at least two inches from the ground. Lacquering will help some, but will not prevent rusting if the cans are close to the ground.
Processing
Nothing has up to this point been said about the processing of 5–gal. pulp. Very few packers process their pulp, and many unprocessed packs have been put up that have not shown over 1 per cent of leaks and swells where new cans were used and the various manufacturing processes were carried out as they should be. In many cases a long shipment of such pulp, after having been stored in a sheltered place for several months, has produced very few additional swells.
One large packer of pulp has for years given his 5–gal. cans a 30–minute process in boiling water, having them pass slowly through a boiling water bath on a chain carrier, the speed of which is regulated so as to give each can the required time in bath. The cans are placed on the chain as soon as they are capped and tipped. Although this packer is very careful in his manufacturing methods he processes as a matter of insurance, principally because a great deal of his pulp is shipped long distances. He must figure that it pays him or he wouldn’t keep it up, as the processing involves quite a little extra handling and extra equipment, and of course has a tendency to darken the pulp somewhat.
Thirty minutes at boiling temperature is, of course, not sufficient time to bring the center of the can near the boiling point, but it will sterilize the can itself and that portion of the pulp which is near the outside. If the pulp is filled very hot, that portion of it which is in the center of the can, being the last to cool, should practically sterilize itself.