Mat Board comes in multiple colors but basically six popularly known variations: Standard Matboard, Black Core, Super White Core, 100% Cotton Rag Mat, Crescent Rag Mat and Bainbridge Alpha Mat. All popular mats I know of are considered acid free by their manufacturers. Only the last three are considered archival quality. All except 100% Cotton Rag are constructed of a top layer, core and bottom layer. Archival Cotton Rag is normally a solid sheet of cotton.

Non-Archival Mat board, the majority of mat board sold in the United States, has a core made of pulp. Since pulp comes from trees it is naturally acidic. It is treated with a chemical called calcium carbonate which "neutralizes" the acid. This effect is not permanent but lasts for many years. Over years depending on environmental factors, heat, humidity, light, etc., the core will turn brownish. The matboard produced today versus even 10 or 20 years ago is much higher quality and an excellent product.

Two additions to standard core, are Super White Core and Black Core. The core has been bleached even brighter than usual. White Core and Black Core mats are particularly striking when used with white surface paper or black surface paper. Photography especially lends itself to these high contrast boards.

The standard for archival mats is 100% Cotton Rag Mat. Because cotton is naturally "acid free". It does not have a surface paper or backing paper. Rather, it is a "sheet" of cotton.

  

100% Cotton Rag is primarily available in shades of white and cream. Although it is available today in grays and even black, the color range of rag is very small because it is a solid sheet and because dyes used in colors do have conservation issues. Hence, major manufacturers have produced archival mats that have the construction of standard matboard so more colors can be made available. The mats receive additional conservation treatment for even more core deacification and more fade resistance dyes. Bainbridge produces Alpha Mat which has a treated super white pulp core. Crescent produces "Rag Mat" which has a cotton core with surface and backing papers. These are both excellent papers offering archival quality and color.

Modern manufacturing is now producing many new core colors in both standard and archival grades. To keep this discussion as simple as possible I have ignored them because their use is limited.

Archival framing is an immense subject involving many factors beyond simply matboard construction. The frame material, type of glass, heat, humidity, mounting and many many other subjects are too complicated to be discussed here. If interested in archival or conservation framing, please see our book section on our online store. If you have framing that has monetary or emotional value requiring archival framing, seek advice from a conservation framing expert.