Most people think that we simply attach a frame to the edge of the mirror glass and attach a hanging wire at the back. There is quite a bit more to it as you will see.
First we need to determine the anticipated weight of the mirror, as determined by size, glass thickness, and frame weight, and where it will hang. If the mirror is large and heavy (it can weigh up to 100 lbs or more) then we need to know that the mounting or wall surface will support it, and that will also determine what hanging system that we use. This can be mirror straps, or aluminum horizontal Z bars across the back at the top, or at the top and bottom if required. These systems are designed to engage the wall studs for strength. If the unit is smaller and lighter then a wire will be fine.
Next we want to determine in what room of the house it will hang - living room, bedroom, bathroom, etc. This will also dictate the type of hanging system used. A large mirror over a bed will require safety hanging devices for instance. A bathroom mirror exposed to moisture will need special treatment before being framed. This will consist of treating the edge of the glass with a sealant, and perhaps creating a moisture trough inside the mirror at the bottom with silicone wedges so it can evaporate out if trapped. For all mirrors, we black out the frame interior so it does not reflect through to the viewer at the front.
Th frame itself can be attached to the mirror glass itself in a number of ways. We can use framers points, Z clips, or non acetic silicone - again depending on the size and application of the mirror. Then determining the style of frame to be used, in relation to the size and weight of the mirror glass is the next step. There are pros and cons all along the way, so talking all of this over with the customer is really helpful.
Finally the thickness and quality of the mirror glass itself needs to be considered, whether or not beveled, and budget considerations. There is a difference in the appearance of the mirror glass depending on source supplier and quality which as always, relates to cost.
Finally it is up to us to bring all of this together and have a happy client when the job is complete.