Bench note
Why solder shows
Silver solder is silver, but it is not the same silver. Under close light the seam will always be findable, and that is not a fault.
Someone once sent a ring back to me because they had found the join. They were not angry, they were genuinely worried something had gone wrong. Nothing had, and it is worth explaining properly, because it comes up more than anything else.
What silver solder actually is
Hard soldering is not the soft, low-temperature soldering used on electronics. Silver solder is itself a silver alloy, with zinc and copper added to bring its melting point below that of the metal you are joining. It is brought to melting with a torch and drawn into the seam by capillary action, and when it cools the joint is as strong as the metal either side. A properly soldered band will bend before the seam opens.
But the solder has a different composition to sterling, so it has a very slightly different colour and it takes polish very slightly differently. Under a lamp at close range, on a bright surface, you can find the line. This is true of every soldered piece of silver ever made, including antique work in museums.
Why not hide it
You can hide it, up to a point. You can file the seam flat, planish across it, and choose a finish that breaks up the light so the eye never settles there. I do all three. What you cannot do is make two different alloys become one alloy, and anyone claiming a seamless soldered joint is either using a laser welder, which fuses the parent metal and is a different process altogether, or is not looking closely enough.
Where I avoid soldering
The best way to have no visible seam is to have no seam. That is why the vessels in vessels and bowls are raised from a single disc rather than made as a cylinder with a soldered side, and why the smaller pieces in spoons and small tools are forged from one bar. It takes far longer. It also removes the question.
Rings are the exception. A band is a straight length of wire bent into a circle, and the two ends have to meet somehow. I close the joint until there is no light through it, which takes longer than most people would guess, because solder will not fill a gap. It flows into a seam or it balls up and sits on top.
The three ways a seam goes wrong
A gap in the joint, so the solder bridges rather than fills. That shows as a bright line and it is weak. The fix is to open the joint, clean it, close it properly, and do it again.
Too much solder, so it floods out onto the surface and has to be filed back. You lose metal and you usually lose the crispness of an edge with it.
Overheating, so the solder eats into the parent metal and leaves a shallow pit. That one cannot be polished out and it means starting again, which I have done, and which is the reason I anneal and solder with the workshop lights off.
What to expect from a piece of mine
On a band, the seam is on the inside where possible, and it should be invisible at arm's length and findable with a loupe. On a soldered bail or a foot ring, the same. If you can see a join across a room, or feel it with a fingertip, that is a fault and I will put it right, which is covered in the terms.
Knowing where the seam is on your own ring is a small pleasure, honestly. It tells you it was made rather than moulded.
In sequence