Methods to substantially reduce or eliminate optical non-uniformity across an interface may also substantially improve the strength and ease of seam manufacturing, including joining substrates. The methods may include managing optical non-uniformities at least by broadening a region over which a change in optical loss may occur and/or by maintaining a substantially constant average optical loss across an interface. The methods may also include forming a seam that substantially reduces the appearance of optical non-uniformities at the seam, which may include maintaining approximately constant average loss in the vicinity of the seam by substantially controlling reflectivity in the vicinity of the seam, in which substantially controlling reflectivity in the vicinity of the seam may include employing a backer treated to minimize optical reflectivity over a range of angles.