Charles Ellicott Commentary Exodus 39:3

"And they did beat the gold into thin plates, and cut it into wires, to work it in the blue, and in the purple, and in the scarlet, and in the fine linen, the work of the skilful workman." — Exodus 39:3 (ASV)

They did beat the gold into thin plates and cut it into wires. This very primitive method of forming gold thread is nowhere else mentioned. It implies a ruder state of the art of metallurgy than we should have expected.

To work it in the blue. The blue, the purple, the scarlet, and the white linen thread were woven into a patterned fabric. The gold was inserted afterwards as embroidery. A similar practice prevailed in Egypt (Wilkinson, Ancient Egyptians, vol. iii., p. 128).