In these days of mass-produced art purchased at Ikea or Costco, preservation is simply not on the minds of many people when getting something matted and framed — and with good reason; most of the art bought is not expected — nor needed — to last ten years, let alone a hundred.
While artwork preservation is the main goal of matting and framing, it is certainly on equal footing with aesthetics in many minds. So the question is: which type of mat should you choose?
ACID-FREE
Terminology and claims can and will vary widely between companies and manufacturers. Before going in, educating yourself can help to make the right choice and to understand the difference in pricing.
The first clarification needed is on the term 'acid-free'. If you do any research into matboard, this term will come up frequently. It will be tossed around for even the cheapest matboard, often giving the false impression that you are buying conservation matboard. Technically most brand-name matboard that you buy will be acid-free. So what's the confusion? To begin with, cheaper matboard — made of wood-pulp — is buffered to be acid-free. Using a buffering agent such as calcium carbonate, the pH (acidity) is brought to a neutral point (7 - 7.5) or slightly above. This buffering agent actively works to prevent acids reaching your art. However, it can only last so long (10 years is a safe estimate). This is fine for many who have bought reproductions or printed their own photos and are not worried about future damage; but if you are framing something important that needs to have lasting protection, simple 'acid-free' matboard is not the way to go. Two examples of this type of mat would be Crescent Decorative matboard or Nielsen Bainbridge Papermats.
ARCHIVAL MATTING
The confusion doesn't end at the low end of the scale. Higher-end matboard suffers from terminology confusion as well. There are two main types of materials used in construction of matboard for archival or conservation purposes: alpha-cellulose and cotton. Cotton is the best material, and is usually referred to as a rag or museum mat. Again, this can vary by company, so it's important to ask if unsure.
Alpha-cellulose
Alpha-cellulose matboard is often known simply as conservation matboard. Alpha-cellulose is made from wood fibers, and is chemically purified (and sometimes buffered as well) to be acid-free. These boards are much better than standard wood pulp boards mentioned above. Two of the biggest brands you may want to look at are Crescent Select matboard and Nielsen Bainbridge's Alphamat series. 100% alpha-cellulose matboards meet the Library of Congress's conservation matting standards. So they fit somewhere in the middle of standard mats and the best museum matboard; a good alternative if you're not looking to spend a bundle, but need to preserve your artwork.
Cotton Matboard
Cotton, or rag, mats are the best for archiving your artwork (outside of spending thousands on a professional conservator, of course!). While quality will vary even between cotton boards, these depend on the manufacturer, so it's best to ask your framer or the company you are buying from if you need clarification. Two of the largest brands of rag mats are by Crescent (RagMat and RagMat Select) and Nielsen Bainbridge (Alpharag). When talking about museum matting, rag mats are what is being discussed. Cotton matboards are naturally acid- and lignin-free, thus ensuring that harm will not come to your art — at least through your matting!
COLORS
One last—but very vital—point should be made regarding the color differences between acid-free and conservation matboard. While the acids of regular mats may not begin to harm your artwork for a decade or more, the colors of the mat will begin to fade, and the core turn yellow—as early as 6 months to a year after framing in some cases. Keep those mats out of sunlight! The reason has everything to do with the color process; standard acid-free mats use dyes (soluble) whereas conservation mats will use pigments (insoluble). The difference after several years can be startling; where one piece may look faded and worn, something framed with archival materials can retain its 'freshness' and look sharp decades after being originally framed.
Hopefully this will shed some light onto the confusing world of matboard. The importance of the right protection for your artwork shouldn't be downplayed, and understanding matting is the first step. Just don't forget the rest of the package; the last thing you want to do is buy the best cotton matboard and use cardboard (very acidic!) for backing. There are conservation-grade materials for every part of the framing process; leaving out one can negate the rest of the process. Now get out there and preserve your work!