The term “molten” does not necessarily mean that the image was cast of solid metal. Such may sometimes have been made, especially of small size; but the metallic part of idols was usually a thin plating of metal on a wooden image. See note on Exodus 32:44And he received them at their hand, and fashioned it with a graving tool, after he had made it a molten calf: and they said, These be thy gods, O Israel, which brought thee up out of the land of Egypt. (Exodus 32:4) (#132). Thus the carpenter and the goldsmith worked together. See Isaiah 40:19-20; 41:719The workman melteth a graven image, and the goldsmith spreadeth it over with gold, and casteth silver chains. 20He that is so impoverished that he hath no oblation chooseth a tree that will not rot; he seeketh unto him a cunning workman to prepare a graven image, that shall not be moved. (Isaiah 40:19‑20)
7So the carpenter encouraged the goldsmith, and he that smootheth with the hammer him that smote the anvil, saying, It is ready for the sodering: and he fastened it with nails, that it should not be moved. (Isaiah 41:7); Jeremiah 10:3-43For the customs of the people are vain: for one cutteth a tree out of the forest, the work of the hands of the workman, with the axe. 4They deck it with silver and with gold; they fasten it with nails and with hammers, that it move not. (Jeremiah 10:3‑4).
The work of the carpenter was to take the rude log and fashion it into an image ready to receive the metallic plates. This is aptly described in the thirteenth verse of this chapter: “The carpenter stretcheth out his rule; he marketh it out with a line; he fitteth it with planes, and he marketh it out with the compass, and maketh it after the figure of a man, according to the beauty of a man; that it may remain in the house.” The figure was first marked on the log with a chalk line, and then cut and carved with the proper tools until it assumed the shape and size required. Denon, in his Travels in Egypt, (cited by Burder, Oriental Customs, No. 720,) speaks of an idol which he found “on one of the columns of the portico of Tentyra; it was covered with stucco and painted. The stucco being partly scaled off; gave me the opportunity of discovering lines traced as if with red chalk. Curiosity prompted me to take away the whole of the stucco, and I found the form of the figure sketched, with corrections of the outline; a division into twenty-two parts: the separation of the thighs being in the middle of the whole height of the figure, and the head comprising rather less than a seventh part.”
It was after some such plan, probably, that idols were made in the time of Isaiah. The wooden image, once made, could be worshiped as it was, or it could be covered with plaster or with metal. On the other hand, the metallic outside might not always have had an interior of wood, but may sometimes have been filled with clay, as idols in India are at tins day.