If you have decorative art, invitations, birth or wedding announcements or other paper items with 3-D elements, sponge mounting is a technique that can be used before framing. Sponge mounting will allow you to flatten the piece and remove any warping or cockling while maintaining the 3-D raised elements. Done properly and by an experienced framer or conservator, sponge mounting can improve severe warping and allow for safe mounting and a nice framed presentation of art and items with 3-D elements.
Sponge mounting can be used for items with raised 3-D elements, such as:
-school graduation announcements
When we refer to 3-D elements, these may include embossed seals or marks, raised designs, decorations, low-relief cast paper designs with soft edges, calligraphy, or monogrammed stationery. Performing methods of mounting other than the sponge technique is potentially damaging to these 3-D elements. For example, traditional dry mounting will not work because the raised areas will get crushed.
With sponge mounting, a dry mount press is used, but with a protective, thin layer of sponge foam overlay. This creates a cushion which should cover the entire area of the artwork, and thus prevents the 3-D elements of the piece from being compressed during mounting. The sponge molds itself to the varying heights of the object to shield it from the pressure of mounting. When sponge mounting is done with a mechanical press, the depth of the platen or heated surface may need to be adjusted to account for the extra layer of foam. In a vacuum or cold press, no special adjustments should be necessary. Do not use a reversible heat activated board for sponge mounting projects as the sponge will leave residue on any exposed adhesive area.
Since the sponge mounting technique is permanent, it should not be used for irreplaceable originals, such as diplomas or certificates. If you have a diploma or document that has become cockled or warped, proceed cautiously in any attempt to flatten it. The primary concern is the long-term preservation of the document, so be sure any steps taken are reversible and will not cause further damage. As with original artwork, a small amount of warping is considered normal, and is preferable to jeopardizing the safe preservation of the document.