To understand what's available in matboard today, it helps to understand the progression that led to this avalanche of choices.  So let's go back and see how we got to where we are today.  As it turns out, America's leading manufacturer of matboard didn't start out making matboard at all.  Crescent Cardboard was just that, a cardboard company, and their stock in trade was signboard.  The light 4 and 8 ply board they manufactured was perfect for making quick, easy signs, and the 32"x40" size they sold was economical, yielding four 16"x20" signs, or sixteen 8"x10" signs without waste.  After the second world war, as America prospered, the fledgling picture framing industry went in search of a low priced alternative to the dense, hard-to-work railroad board used in traditional European matting.  Crescent and its signboard seemed perfect.  But from the start there were obstacles.

The Problem of Acid
 

Signboard was available mostly in white or offwhite.  In order to approximate the decorative flexibility of European matting, where the board is wrapped with colored paper or fabric to conceal the ugly gray core board beneath, Crescent's board would have to be available in different colors.  But a dearth of colors wasn't the only obstacle.  Signboard was constituted of several laminates (or plies) of paper made of wood pulp.  Unfortunately, paper made from wood pulp is not long lasting. 
 

Ah, but artwork is supposed to be long lasting and the framing that surrounds it, if it cannot enhance its longevity, at least ought not to detract from it.  But wood-based paper is informed with a binding polymer called lignin.  Lignin is the stuff that actually holds wood together.  In direct sunlight and high humidity, and given enough time, lignin can break down, producing acid, which can seep or "migrate" out of the product it is in, and pass into any other product it is contact with.  At the point of contact a brownish hazy affect can occur called "acid burn".  To make matters worse, acid burn is a stain that cannot be removed and which signals the beginning of an ever worsening deterioration.
 

To the utter chagrin of professional framers in the 60's and 70's, the potential of matboard to have this affect was confirmed.  The reason it had not seemed such a big problem at first is that acid burn (or acid contamination, as its sometimes called) is a process that can take between fifteen and twenty-five years to manifest itself fully.  So, suddenly, in the late 60's professional framers were confronted by angry customers demanding to know what had been done to their artwork fifteen or twenty years earlier.

Rag Matboard

While the matboard manufacturers went to work on the problem, they advised picture framers to safeguard artwork by providing barriers between the acid bearing constituents and the artwork.  Any cotton based paper would do, since cotton contains little or no lignin.  Such papers came to be referred to as barrier papers, and the practice of inserting barriers between lignin bearing materials and artwork came to be known as conservation framing.
 

But matboard companies didn't leave it at that.  They went to work developing an alternative matboard, one in which the core of the board would be made of cotton rather than a wood-based paper.  The first cotton core matboard was made by Crescent and was actually manufactured from recycled cotton rags, which is how it got its name, Rag Mat.
 

Using Rag Mat, framers could return to placing the mat in direct contact with the artwork and forego the time consuming practice of cutting and placing barrier papers between the mat and the artwork.  Yet the cat was out of the bag, so to speak.  The horror of finding professionally framed artwork ruined after years of hanging innocently on the walls, had made many framer's gun shy.  Particularly those with the most to lose, such as museums or those framing expensive original art.

Museum Rag Matboard
 

It was pointed out that the problem with acid was not just that it seeps into that which it was in direct contact with, but that it can contaminate the next item to the extent that the item itself becomes a threat to whatever it is in contact with.  In other words, acid can migrate from layer to layer, and given enough time, work through barriers.
 

The matboard manufacturers quite reasonably pointed out that such migration through barriers could take well over a hundred years, but the museums were still concerned.  After all, their artwork needed to be protected for many hundreds of years.  Also, they pointed out, Rag Mat was not strictly speaking, 100% lignin free.  While the core board and backing were indeed made of cotton and thus acid and lignin free, the face papers that were laminated onto the core to give the board its color and texture were the same wood-based face papers used in regular matboard.  Couldn't, therefore, acid migrate out of the face paper, contaminate the core and eventually become a threat to the artwork?
 

The matboard manufacturers agreed that this was possible, albeit highly unlikely in the short term, and took measures to address the issue.  By putting the wood-based face papers through a bath of calcium-carbonate, they were able to balance the pH rendering the acid content in the face papers "neutralized".  In other words, the face papers still contained acid, but the acid could do no harm, or at least not until acids floating freely in the air assaulted it for such a prolonged period that the pH became unbalanced again, favoring the acid.  This, they pointed out, could take as long as a century.
 

Yet many museums were still unsatisfied.  What they wanted was a matboard that was 100% lignin and acid-free through and through.  Moreover, they wanted the lignin-free, acid-free matboard neutralized to protect against free floating acid in the air.  The matboard companies obliged, coming up with a new product for the ultimate in protection, the aptly named Museum Board.  Or, as Crescent calls it, Museum Rag 100 - meaning 100% protection.

Regular (Decorative) Matboard
 

At about the same time the matboard manufacturers took measures to end the nightmare of acid contamination resulting from use of their regular wood-based matboard.  Beginning in the mid-1980's they began putting all of their matboard through a neutralizing process, rendering the acid content harmless for a period of perhaps as long as a hundred years.  Today, all the matboard in Crescent's regular matboard line, called Decorative Matboard, has been acid-neturalized in this way.

Berkshire (Value) Matboard

In the 1990's a growing demand from mass merchandisers for low priced matboard that could be used in gift frames and department store framed art led to the development of the Berkshire line of regular matboard.  Berkshire is Crescent's value line. Designed principally for large volume producers, Berkshire is slightly thinner than regular 4-ply matboard yet has the same acid-neutralized core as Crescent's most popular Decorative line, meaning it's safe for the same artwork you would mat with regular matboard.  An excellent alternative for those striving to hold down the cost of framing, the difference between Berkshire and Crescent's regular Decorative matboard is virtually indistinguishable unless the two  are held next to each other and analyzed closely.  Since the Berkshire we carry is a "white core" variety, Berkshire's bevel is brighter white than the cream core of regular Decorative matboard, a feature generally considered a premium feature since it is most closely associated with Rag Mat.  For those seeking to maximize profit margins to cover overhead costs, Berkshire may not be the best bet (as lower costs mean lower relative dollar volume) but for those seeking to hold down the cost of framing, or anyone looking to appeal to customers on the basis of a lower price, Berkshire is the answer. 
 

In any case,the acid problem which had afflicted matboard manufacturers since the industry's inception had at last been thoroughly addressed and four distinct types of matboard emerged: Berkshire (value regular) Matboard, Decorative Matboard (standard regular, Rag Matboard, and Museum Rag 100.  While Museum Rag 100 is largely limited to whites, blacks and neutral tones (with a few colors salted in), the Berkshire, Decorative and Rag Mat lines are offered in a full range of more than 200 colors.  Approximately 50% of the colors are the same in the two lines, with 50% being unique to whichever line you're considering.