Matboard and backing do different jobs.

Separate the window from the support.

A window mat surrounds an opening that exposes part of the artwork. A backmat or support sits behind the object. A further backing layer can protect the assembled package. The names used in retail vary, so ask what each supplied component does rather than treating all boards as interchangeable.

Foamboard can be sold for backing, mounting or other projects. The generic name alone does not establish its chemistry, surface, stiffness, thickness or suitability for contact with a particular object. A calculator that knows only width and height cannot make that determination.

Read preservation guidance in its context.

The Library of Congress describes preservation matting and framing for paper-based collections. It calls for chemically stable components, adequate depth and separation between the object and glazing. Its recommendations address limiting damage to collections, not a guarantee that every retail product bearing an archival label meets the same conditions.

NEDCC likewise explains preservation materials and framing practices for works on paper and photographs. It cautions that general marketing terminology is insufficient evidence of performance. Ask for actual material specifications and suitability for your medium; photographs can have different contact-material requirements from other paper objects.

Within its preservation context, NEDCC advises against foam boards, including products marketed as archival, and recommends cotton rag for the window and primary backing. Treat that as preservation guidance for its stated objects, not a claim that every board sold for general craft use is interchangeable.

Do not infer thickness from a label.

A ply description does not give this tool a verified physical depth for the actual product. Use the manufacturer’s measured thickness and include all layers when checking the frame. The frame needs space for glazing, mat layers, artwork/support and backing as appropriate to the assembly.

The comparison tool does not include stack depth or flexible/warped components. A board row marked as a geometric fit is not a material or conservation endorsement. No board brands or products are ranked or recommended here.

Geometry does not decide mounting.

The tools do not recommend adhesive, tape, trimming, hinging or attachment methods for your artwork. Those choices depend on the medium, paper, value, condition and intended display. Irreversible attachment can matter far more than a border calculation; consult a suitable professional for an original or sensitive object.

Preservation framing also does not stop all damage from display. The Library of Congress warns about light exposure and suggests considering a reproduction for long-term display of valuable paper collections. A larger mat or a UV-related product label alone cannot establish that a display is safe.

Questions worth taking to the framer.

What materials touch the artwork? Are they appropriate for this medium? How will it be attached, and can that method be reversed appropriately? What space keeps it away from glazing? Will the full stack fit the actual frame, and how will it be secured? Record those answers separately from the geometric worksheet.