Efficient copper concentration via froth flotation hinges on balancing collector selectivity, frother strength, and slurry density to maximize concentrate grade at acceptable recovery and cost. This study systematically evaluates two collectors, namely K1 and K2 with a common frother across pulp densities of 34, 42, and 48% solids by mass. Batch laboratory froth flotation tests were executed under controlled hydrodynamics with rigorous, reproducible sample preparation, calibrated chemical dosing, and time-resolved concentrate pulls. Kinetics, cumulative recovery, froth stability, and grade-recovery curves were computed to quantify performance. Raising solids from 34 to 48% increased concentrate grade but depressed overall recovery, consistent with higher pulp viscosity, reduced bubble mobility, and shorter froth residence favouring selective attachment. An operational optimum emerged at 42% solids: grade improved relative to 34% with only moderate recovery loss, yielding the most cost-effective outcome when reagent consumption is included. At 34% solids, recovery was highest but concentrate grade was diluted; this regime suits scenarios prioritizing metal units. At 48% solids, selectivity improved further but recovery penalties became prohibitive. Across densities, Test 2 employing a higher-activity selective collector (K1-based) with tuned dosage outperformed alternatives, delivering superior grades at equal or better recoveries. Relative to K2, the selective regime reduced gangue entrainment and stabilized froth morphology in conjunction with the frother, enabling cleaner, faster flotation without excessive reagent addition. In conclusion, results show that (i) density is a first-order lever governing the grade recovery of copper through concentration by froth flotation; (ii) selective collector chemistry, properly dosed, shifts the frontier upward; and (iii) an operating window near 42% solids with a K1-dominant collector suite and moderated frother addition provides robust performance and lower unit reagent cost. These insights further support reagent and density set-point optimization in industrial circuits targeting higher-value concentrates with controlled chemical spend.