What silver to use for ring making ?

in our silver class we use 99% pure silver to increase strength and color that lasts when it is processed into jewelry and if you use 99% pure silver when you want to remake a finished ring and melt it back to make a different design then you will be able to do it. the same is true with the quality of jewelry that uses 925% silver when a piece of jewelry uses 925% pure silver you will have a harder time melting it and making a redesign again because 925% silver already contains a mixture of copper around 7.5%