by raimundo » 21 Jan 2007 13:02
the concept is centuries old, besides clay, there are other materials, eamon devalera escaped from kilmainham jail with a key that was made from an impression pressed into a wax candle. perhaps something relatively cold like plaster of paris was poured into that impression to make a copiable positive of the negative imprint, or perhaps only a caliper and the imprint were used. its an excellent method for fiction writers, but a bit twitchy in real use. most of the materials that have to set up to harden (including molten metal) will have a bit of shrinkage,
the other day, I was playing around with the metal that comes on the top of wine bottles to wrap the cork, it can be made into an impression that will carry the information but cannot take any kind of working other than caliper measurements, and the piece is delicate to carry. I wonder what the melting point of this metal is? it seems a lot like lead, except that tearing it is harder than I would expect from lead foil, and of course would lead be used in food packaging. by the way, food packageing, the plastic foam trays that meat cuts are on will take an impression, and of course, a pack of wrigleys winterfresh gum provides 5 flat pieces that can be impressed directly into the foil with the gum inside. there is an obscure dental technique in which gold amalgum is not used but gold foil is used to tightly pack a cavity by crushing the foil in. try smoothing out a piece of aluminum foil, and wrapping it carefully around a key blank then put it in a solid form, like a steel ring set on a flat steel base, put crinkled foil on top of that and push it down tight, til the ring is full to the top, then lift the ring and turn it over, and put more foil on the other side, press it in as tightly as possible, the add a pile of crushed foil on top of that, til it comes well over the top, cover this with a cloth to keep it all in place and start hammering on the pile with a rubber hammer, do not hit hard, hit often, this is the action that will really pack that foil tight. the original flattend piece of foil wrapped on the key should be the separation layer, you will probaly have to learn from the first try how to improve it. take a coin and put aluminum foil around it, then with the eraser of a pencil, press the foil down until it is absolutely smooth, do not rub, press and lift and press, this will show one of the basic concepts.
