If your mat board is of an economy grade we recommend the white rpb boards or for something thicker the standard or acid free foam core offers more support for larger artwork.
Acid free mat board difference.
Rag mat boards come in 2 thickness 2 ply and 4 ply.
If you do want to provide additional barrier between the print and the foam you will want to use 100 cotton rag mat board which is naturally inert.
The core backing and surface paper are acid free.
The core and back of the board are acid free but not the surface paper.
4 ply is roughly the same thickness as regular mat board.
For any original artwork we recommend a conservation quality backing to go with any conservation or museum grade mat board.
What does acid free actually mean.
What you need depends on how archival you want to get.
Backing is used to provide support and protection for your artwork either in a picture frame or as a standalone product in a show kit we offer economy pressboard standard matboard backing archival quality backing foam board regular and acid free as well self adhesive archival.
The mat board companies obliged coming up with a new product for the ultimate in protection the aptly named museum board.
Rag mat board is made from cotton.
Moreover they wanted the lignin free acid free matboard neutralized to protect against free floating acid in the air.
Backing boards come in any size.