Once the hands CAD design was done we had masters ‘printed’ in resin, from which rubber casting moulds would be made. It was quite incredible the amount
of detail that had been built into such a small size (the hands measure about 21mm). To the left here is the CAD rendition and to the right the resin ‘print’.
Our hands pins are cast using the ‘lost wax’ casting process, an ages old procedure used for the crafting of fine jewellery. It’s a laborious, slow and non-compromising
process, but will provide the best results and a 3D shape. It all starts with waxes – one for every single casting, the waxes built into a ‘tree’.
The completed wax trees are put into metal casting flasks, a fine clay like ‘investment’ powder then added to the hopper with water. Once thoroughly
mixed the slurry is poured into the flasks, where it will harden. The flasks are then heated inverted in an oven to melt the wax and allow it to run out,
leaving a void into which later molten metal will be poured to become the vacated shape. Hence the term “lost wax”.
A section of 1939 vintage Duralumin Spitfire main spar is heated until it becomes molten at around 700 degrees centigrade.
Once liquid the hot metal is poured into the previously made casting flask.
The flask is allowed to cool for a few minutes before being dunked into a tub of water to soften the
casting compound. Here the freshly cast ‘tree’ of clapping hands elements is still half embedded.
A tree of around 110 clapping hands cleaned of compound, now taking the form of the original wax tree. The hands will be cut
off the trunk and go to the finishers, whilst the offcuts will be used again, this historic and finite metal too precious to waste.
At our finishers in Birmingham the sprue is removed, the hands fettled, barrelled to impart
an initial mechanical polish, pin attached to the back and then given a final hand polish.
The very last procedure to be done is to laser engrave the text on the back, NHS “Thank You” 2021.
Christopher Bennett of TMB Art Metal, creator of The “Thank You” Pin project, with some of the very first casts.