What a positive or negative spread means
A positive spread means gold's positioning is further right on its own historical distribution than silver's: speculators are more convicted on gold. A negative spread means silver is the more extended contract. Since gold and silver often rally together but silver has higher beta, a negative spread (silver more extended) can show up late in a precious-metals rally as silver starts to catch up. Historically, a wide silver-extreme reading has been a topping signal.