Wondering if anyone out there knows anything about the concentration of Glyphosate Weedkiller. I recently bought some of the sachets you dissolve in a litre of water, and apply with a sprayer/watering can. They were an Amazon lightning deal (and I had some leftover vouchers, so didn't cost very much), what I'd like to know is, can I add more sachets to water to make the stuff more concentrated ? Will the resulting stuff work better on my brambles? Or would I just be wasting my money by making the mixture stronger?