[Sparrow Industrial Pictures Ltd. photo. Hot caps may be made from white waxed paper ready cut to size, 23in. x 22in. The cap on the left is made by folding the paper into four and stitching up one side. The cap on the right is made from the same paper and is reinforced by two 4in. strips of similar paper placed crosswise from corner to corner and attached by running a hot iron over the whole sheet. This operation, beside attaching the strips, also warms up the waxed paper and makes it pliable for putting over a mould (an old car headlamp is suitable for this purpose). After it has been over the mould 1 or 2 minutes the cap is removed. For ventilation a hole 1in. in diameter is made in the side of cap.

New Zealand Journal of Agriculture, Volume 79, Issue 3, 15 September 1949, Page 200

[Sparrow Industrial Pictures Ltd. photo. Hot caps may be made from white waxed paper ready cut to size, 23in. x 22in. The cap on the left is made by folding the paper into four and stitching up one side. The cap on the right is made from the same paper and is reinforced by two 4in. strips of similar paper placed crosswise from corner to corner and attached by running a hot iron over the whole sheet. This operation, beside attaching the strips, also warms up the waxed paper and makes it pliable for putting over a mould (an old car headlamp is suitable for this purpose). After it has been over the mould 1 or 2 minutes the cap is removed. For ventilation a hole 1in. in diameter is made in the side of cap.