Unlike many works (such as photography) stretched canvases do not generally require an external frame or acrylic/glass protection to protect them. Many clients will simply have their canvas stretched with no additional external frame.
At Merlin, we also specialise in working with valuable artwork, many of which tend to be oil or acrylic on canvas. Due to the value of the artwork, many of our clients prefer to add an external frame in addition to the stretching services to give the completed work that little extra shine.