Base metals shrugged off a momentary technical correction during Wednesday afternoon London Metal Exchange (LME) trading, resuming this week's uptrend to notch up new highs, traders said.
"It got very busy this afternoon again - the speculators have got their buying boots on at the moment," a trader said.
Major metals aluminium and copper hit new five-month peaks, but lesser metals lead and zinc were also in the spotlight, touching seven-month and six-week highs at one stage.
Although the markets are looking overbought, an influx of positive sentiment is keeping upward momentum intact.
Sporadic large inventory increases are seen as one-offs, with the overall trend one of falling warehouse stocks and backwardations in nearly all markets.
"There is not the same willingness to short the market as there is to go long at the moment. So the dips look a bit tentative, especially when the buying comes back in," the trader said.
Copper was erratic, hitting highs in excess of $2,940 overnight in Asia, then tumbling back under $2,900, only to recover on the kerb. Final three months business was at $2,915 a tonne, up $15.
"It needed to close above $2,900 on the charts - it has done that, so we should get another crack at $2,940/2,950," the trader said.
Analysts said an impasse in labour contract negotiations at North American copper producer Asarco was providing support.
Asarco, a subsidiary of Grupo Mexico, produces around 150,000 tonnes of refined copper per year.
Aluminium see-sawed around $1,800 for most of the session before rising to end at $1,810, up $8.
Lead was unable to sustain an advance above $920, but still closed $9 higher at $915. Zinc was erratic as well, trading in a wide band some $15 either side of $1,000 before last trade at $1,016, up $42.
Nickel rose $775 to $14,150, while tin was $25 higher at $8,975/9,025.