Though we are not often visited by a spell of very hot weather, when one does arrive it is very useful to have some means of preserving perishable provisions and preventing butter becoming almost liquid.
The chest illustrated by the two diagrams following can be made cheaply by any handy person, and will be found quite efficient. It is shown in longitudinal section in Fig, 1. An inner casing, lined with zinc, has two frames A and B attached to it; and to the outside of the frames are nailed boards forming an outer casing, which projects downwards 2 inches beyond the bottom of the inner box. The spaces between the two casings are filled with sawdust, slag wool, or other insulating material.
The lid is a framework c, strengthened by a crossbar D, boarded top and bottom. Its under side is covered by a sheet of zinc.
Since the ice used for cooling must melt by degrees, a drain pipe, turned up at the end to make a water-seal which will prevent the escape of the cold air, is provided. The bottom slopes down slightly in all directions towards the top of this pipe, so as to be self-draining.
A sound Tates sugar bos does well enough for the inner case. Its internal measurements are roughly: length, 19 inches; width, 14 inches; depth, 17 inches. The ledges on the inside at top and bottom of ends will have to be removed. But before removing them tack temporary strips on the outside, and clear of the areas which frames A and B will touch. Drive a few extra nails through the bottom to make it fit closely to sides and ends everywhere.
Next, construct frames A and B, which must fit the box closely, and be screwed on flush with the top and bottom with screws inserted from inside.
Nail in the bottom inside angles slips of J-inch wood for the edges of the lining to rest on; and paste brown paper all over the outside of sides and ends, to prevent the insulating material working through joints.
The Zinc Lining
Anyone lacking experience with a soldering iron had better leave the making of this to a professional tinsmith. If, however, he feels capable of the job, he should proceed as follows. The bottom is a closely fitting tray with edges turned up & inch, but not quite squarely, so that when placed they shall press against the wood. Before putting it in position, make a £-inch hole for the drain pipe and beat the edges of the hole downwards into a slightly conical form.
The ends have their bottom and vertical edges turned in I inch, and rest on the bottom. The sides, or back and front, are turned over I inch at the bottom only, and overlap the vertical flanges of the ends by ½ inch. These vertical edges are drilled with a few small holes – remove any burr at the back – for brass tacks to hold them snugly up against the end flanges and make soldering easier.