Backsides of some pendants
When enameling copper, the background for the glass tends to be reddish to red, whether for the metal color itself, or, more pronounced, for the cuprous oxide facilitating glass-metal bond.
An attempt was done to replace copper with aluminium. The attempt failed due to too low melting point of aluminium. However, an interesting effect was observed - the metal in the flame forms a fairly thick crust of oxide, which then encapsulates the molten metal and holds it roughly in the original shape. The oxide layer however deforms, allowing the molten metal to achieve a somewhat different shape, distorting the contours and creating a characteristic surface structure. The metal also fairly well adheres to molten glass, perfectly conforming to its shape.
It was also found during the initial tests that the molten glass burns through the metal layer onto the substrate (a piece of Cerablanket high temperature insulation wool laid on a firebrick).
This effect, a form of plique-a-jour, makes the glass look brighter and prettier. The effect was therefore strengthened, first with drilling a lot of closely spaced holes (so there is less metal to be displaced with the glass and the displacement is easier and more complete), in later version just by drilling out the contours and then roughly cutting out the shape with an art knife or wire cutters.
The removal of the center part of the underlying metal sheet, whether partial (drilled holes) or total, reduces the problems with warping of the molten metal, as there is less metal to be displaced towards the edges and inflate and deform the oxide crust.
When manipulating glass in molten state, either to alter its pattern, remove surface contaminants, or facilitate spreading over the metal frame, it has to be considered that the molten metal has MUCH lower viscosity, and be very careful especially when operating around the hole for the hanging assembly. Two pendants were inadvertently damaged during such tweaks, and their eyes were destroyed; repair is scheduled.