Nitric is too strong, it needs water, to form HNO2 in solution, and too strong of nitric seems to passivate the silver.
Strong acids and dilute acid can react completely differently on metals.
Adding water same volume as the nitric acid will dissolve more silver, a 50:50 mix of 70% HNO3 : water, if diluted more than this with water or 3% H2O2 the nitric would take longer to react but the reaction of red fuming gases would be less, more of these gases stay in solution to dissolve more silver, and more of your silver would react with the gases mixing with water to re-form nitric acid in solution instead of fuming off in a red cloud of NOx gas, the added extra water can also allow for heating the solution with out concentrating the nitric to where it is too strong to react with the silver effectively or fuming off as NOx gases, heating will also help to make the reaction go faster and to completion, a 3% hydrogen peroxide can also be used to dilute the nitric further instead of the added extra water, the oxygen in solution with the water helps to keep the gases in solution and rejuvenating giving oxygen to nitrous oxide gas to form nitrous dioxide gas which mixed in water forms nitric acid to dissolve more silver, making your nitric go further, and to completion, without leaving you with unreacted nitric acid when you think it has completed reacting (or reaction is less visible)
Cold nitric when almost consumed with metals like silver will slow down to a crawl, before the last of the nitric is consumed to make metal nitrate salts, heat can make this go faster, when you think all of the nitric acid is finished dissolving silver, the reaction slows and is less visible, heating the solution will concentrate the unreacted nitric and dissolve quite a bit more silver, if you start to see red gases fuming off adding a little more 3% H2O2 can help to keep free HNO3 reacting to dissolve silver, if copper is involved the green solution will also turn blue another indication most of the nitric is reacted.
The green is copper and nickel the nitric in solution unreacted seems to color it green possibly from NOx in solution and concentrated unreacted HNO3.
If you take a little of the green solution from the fingers in a test tube or small vessel and dilute with equal volumes or more of water and add a small copper wire, the solution will dissolve the copper, once all of the free nitric reacts (dissolved all of the copper it can which may take either time or heating the solution will turn a blue solution of copper nitrate.
At first the nitric reaction is exothermic and will generate its own heat, so no added heating is needed, add heat at this point can make too much gases form and not only wastes HNO3, but can boil over a solution spilling your metals, but after much of the nitric is consumed the heat of the reaction slows, there is still a lot more free nitric which will dissolve a lot more silver, now adding heat is needed to finish the reaction, if we did not finish the reaction with heat, we would have a lot of unreacted HNO3 which would consume more copper later when we go to cement out our silver from this solution.
If the silver and nitric or silver nitrate solution is too concentrated silver nitrate crystals will form, these are water soluble so extra water can keep these in solution, as any remaining nitric can attack silver, also having the solution dilute even after all of the free nitric is reacted will keep silver dissolved and can help when cementing out the metals from solution later.
I hope I explained this to where the idea is understandable
