All double mats will have the color black as the bottom mat, overwhelmingly the preferred choice when framing diplomas or other documents. Our mat margins are 2" to 3" depending on overall mat size.
Starting with outer to inner:
1) 99% UV glazing – conservation glass or acrylic
2) 100% cotton rag matting – no wood pulp or filler is used
3) 100% cotton rag backing – the diploma should rest on true cotton rag material
4) Final backing in archival grade chloroplast – Never use any foam core or commercial (contains acids or outgasses) board
Alpha cellulose board which some non-purists may allow is still wood pulp board that has been chemically treated. It’s like the difference between buying organic verses artificial ingredients with preservatives.