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If silica is melted and allowed to cool slowly, the result is 1_______. Glass is more difficult to make than pottery, and the first all-glass containers did not appear until 1500 BC. Glass was made then by melting raw silica held by a glass thread on a sand core to form a bottle or shaping it in a mould. It was not until 2_______ that the technique of blowing glass was developed. A wine glass was made by blowing melted glass in a mould, adding a stem, shaping the foot and trimming. Press moulding is an even more 3_______ technique.
Glass-working tools include a blowpipe, rod, tongs, shears and rolling plate. Glass was originally melted in a furnaces were 4_______.
glass
1350 BC
modern
used