Should I use buffered or non-/unbuffered materials (matboard, interleaving sheets, etc.) with my digital pigment prints?
The Short Answer
This is a common question I receive from clients and an area of obvious relevance. Surprisingly, after researching this subject, the answer to this question was not as clear cut as I anticipated. After performing my research, I intend on recommending buffered materials for use with digital prints.
The Longer Answer
The explanation of how I came to this conclusion starts with a few definitions. First, buffered materials are materials in which calcium carbonate (a chalk) or a similar material has been added to paper pulp during the paper making process to act as a buffering agent. The calcium carbonate raises the pH level of the resulting material to the alkaline side of things, making it non-acidic, and acts to counter acidic substances or pollution in the environment (such as smog) from impacting the buffered material. Many inkjet papers themselves are buffered for this reason.
Historically, archivists preferred buffered materials for conservation purposes to help combat acid from materials in the environment unless a particular material required non-buffered materials around it. The most common exclusion from being used with buffered materials is any item with components made from animals (i.e., protein-based materials), such as silk or leather. Photographic prints in this category include albumen prints, cyanotypes, and dye transfer prints because of their component materials.
An article Jeffrey Neumann from Picture Framing Magazine (link to PDF here) explains the history of the buffering issue as applied to photographic prints (more info also from Wilhelm Research). In the 1980’s, many conservators started recommending non-buffered materials for use with albumen, cyanotype, dye transfer, and chromogenic (color) prints by extrapolating from damage done to various albumen prints in storage. Additional research in the 1990’s by the Image Permanence Institute – the same researchers who made the initial determination that buffered materials were the culprit – led to the IPI to withdraw their recommendation to use unbuffered materials.
They now contend that either buffered or non-buffered are acceptable for all photographic prints except for dye transfer and cyanotypes. The IPI now instead recommends the use of high quality materials — Museum quality board, acid- and lingin-free, and able to pass their Photographic Activity Test (PAT). They also recommend buffered materials for photographic enclosures (which would include matboards and interleaving paper) as a means to help prevent acid from an enclosure from damaging a print and possibly to help absorb environmental acids.
Information from resellers and manufacturers also support the use of buffered materials with digital prints. Archival Methods, one of the big suppliers of matboard and tissue, suggests using unbuffered materials only for dye transfer and cyanotypes. Resellers such as B&H also say this, though they may simply be parroting what manufacturers such as Archival Methods tell them. University Products also has a nice article on this issue and comes to the same conclusion. (I did find at least one retailer, Light Impressions, that seems to have contradictory advice – recommends buffered but at least in one location says to use non-buffered for chromogenic prints. Given the other information I found there and elsewhere, I think it is likely sloppiness that chromogenic prints are listed there.)
Despite this history, many conservators and others recommend unbuffered materials for use with digital prints. I suspect the reasons for this vary by individual, but a lack of compelling evidence to change their recommendation might be factor (even if the original recommendation for non-buffered had much weaker evidence). I will say that the evidence is not overwhelming — it is not clear to me that anyone has done systematic, long-term research on this issue — but the weight of evidence and theory right now is that buffered materials are better for digital pigment prints.
Does it Even Matter?
A consensus also seems to have formed around the fact that the buffering issue is actually not that important for digital prints — many other factors are much more important in determining print longevity, including exposure to light or sunlight, humidity,temperature, the particular paper and ink combination, and the like. Mark McCormick-Goodhart of Aardenberg Imaging & Archives (which I think to be the best source now of info on digital print longevity) emphasizes the unimportance of the buffering issue in a post on the Luminous Landscape forum. Here’s what he says:
The major factors determining your print longevity are your material choices for inkjet paper,inks and possibly coatings combined with the actual environmental conditions, ie., the light intensity on display, the temperature on display or in storage, and the relative humidity on display or in storage.
Picture frame glazing, matting and mounting (which should be specified acid and lignin-free but largely irrelevant whether buffered or unbuffered) goes a long way to reduce the external air pollution effects. Note that some companies marketing conservation quality matt board will have their products also certified with the PAT test (photographic activity test) that is available as a testing procedure at IPI (the Image Permanence Institute in Rochester, NY). It’s a worthwhile test for silver gelatin print processes, certainly doesn’t hurt and may be beneficial for some ink jet print processes if the matt board passes it.
Mark also provided input on the dpreview discussion boards along similar lines:
For pigmented inks, the buffered versus non buffered question is a rather academic discussion, as the pigment particles are not going to migrate from acid to base conditions which is what can possibly happen (under high humidity conditions) when acidified dyes come in direct contact with an alkaline buffered tissue or mount board. Buffering agents in rag board are typically materials like calcium carbonate. While buffered mat board can protect against “acid burn” from external polluting sources (No3 and SO2 gases from urban smog, etc), it won’t stabilize wood pulp papers with lignin remaining in the bulk material, etc. I’ve seen many “archival” mat boards that don’t live up to their marketing hype. Stick with reputable manufacturers of mat board and papers, and consider the non-buffered materials if you are matting and storing dye-based inkjet materials. Otherwise, either buffered or non-buffered will be OK provided, as Neil also noted, the inherent processing during manufacture was done well.
My recommendation is to use buffered materials with your pigment-based digital prints, but non-buffered materials should also be fine if you want to go that way. I’m personally more convinced that buffered solutions are superior and will accordingly use them for my own photographs and will also recommend them for my clients going forward.