I’ve always joked about thumbtacks for mounting. If regular thumbtacks are considered dry mounting, then stainless steel thumbtacks must be conservation mounting. And if that’s the case what makes them conservation and where are the archival thumbtacks? And how do archival ones differ from conservation ones?
Archival vs Conservation
Archival historically was defined as "of or pertaining to archives"…great definition. By today’s standards and as defined by FACTS in MATBOARD AND GLAZING STANDARD TERMINOLOGY, the term is loosely used to refer to materials that can be used without hurtful or harmful effects in the conservation or care of important artifacts. Conservation, as used with framing for display purposes, defines in the same book as work done using methods and materials designed to maintain conditions and longevity of an item.
If conservation framing techniques are to be appropriately followed, archival quality materials are required to conserve (or preserve) and therefore assure long term survival of any given artwork or photograph. In other words, anything we do when framing a customer’s art must not do any short or long term damage, encourage deterioration of any kind, or alter the art in any way from its original. Granted this is my understanding, but it becomes the source of the whole archival dry mounting dilemma, which is truly an oxymoron. How can archival and dry mounting be used simultaneously for mounting descriptions of the same project? Based on the FACTS definitions as noted above, merely maintaining the existing conditions of the art is a conservation approach. But looking closer, that also means not altering it in any way from the way it has been received.
Archival Tissues Too?
It stands to reason, that if an adhesive is absorbed into any limited edition artwork, fabric, or fiber based photograph it is no longer in its original state, thus not "maintaining the conditions of the item." This is indeed the nonarchival, nonconservation problem with all of the marketed archival dry mount tissues produced in our industry today.
Manufacturers have developed wonderful breathable (porous), low temperature, removable—NOT REVERSIBLE—dry mount tissues using derivatives of the word archival for years…in fact long before the big conservation/preservation brouhaha. ArchivalMount (Seal Products), Drychival (Drytac Corporation), ConservaBond (Corona Products), and Archival Quality Dry Mount Tissue (Hot Press Supplies) are all examples of marketing product names that only serve to confuse us in our quest for, and selection of, proper and safe archival products. Dry mounting and conservation practices cannot be describing the same mounting techniques on the same project.
Other archival or conservation tissues and films are also available but do not feature the archival word in their name including, TM4 (HUNT Corporation), and SafeMount (Print Mount), which are much more correct in their marketing presentations to us. They are as promoted, more delicate, but not really archival.
Archival Realities
Product descriptions of the above products generally run the gamut from "…acid-free, buffered tissue…helps protect artwork from environmental degradation…the pH level of this product has been tested to TAPPI Standard T435 (TM4)" to "a thermal setting (permanent) low temperature adhesive…is formulated especially for Archival quality dry mounting. For preservation applications…use with quality substrates and mats. (Corona)." The issue is not the pH so much as altering the artwork through adhesive absorption and residue.
So, if a product uses the term archival in its name is it stating the materials used to produce it are harmless to any art the same as using conservation standards? In actuality yes. The products, tissues, and adhesives will not age, yellow or accelerate the deterioration of an artwork in any way, that is perhaps what qualifies it as archival, but is also what makes it non-conservation.
Archival Explanations
When conservation/preservation mounting with cooked wet starches, the adhesive and technique is entirely reversible to the point of always being able to return the art to its original state. It is the absorption action and saturation of the adhesive into the art when dry mounting that is not a true preservation technique.
By ‘archival’ definition these dry mount adhesive tissues may indeed carry the archival term in their brand names simply because they will not produce hurtful or harmful (deleterious) effects or results. There are a number of factors that need to be examined and/or explained in order to truly understand the archival term, yet lack of conservation. Adhesive composition, carrier pH, time/temperature ratio and permanence of application are all important.
Adhesive Composition and pH
The chemical definition of inert materials, as defined by Webster’s Dictionary of the English Language, is that "having little or no ability to react or effect." Most dry mount adhesives themselves are considered inert, meaning they contain no harmful acids capable of damaging what has been mounted.
It is actually the carrier sheet or tissue-core which needs to be checked for pH level. The pH scale runs 0 (acid) to 14.0 (alkaline) with 7.0 as true neutral. Most accepted buffered materials are required to be held at 7.0-8.5 in order to qualify for neutral or acid-free range notations. Dry mount adhesives fall into 7.0 as inert, with buffered tissues at 7.5-8.5.
As mentioned above, numerous manufacturers have developed tissues using acid-free or in most cases acid buffered, carrier papers in conjunction with the inert dry mount coated adhesive. This then allows them to be considered archival quality.
Generally these neutral pH tissues are also porous for use with most any item that can be mounted using heat. That means they may be used for mounting both porous and nonporous delicate items including thin papers, fabrics, fiber based and RC photographs.
Time/Temperature Ratios
Archival quality tissues generally mount at the lowest suggested temperatures of all dry mount adhesives. These archival wannabe adhesives are also considered much more delicate because of their lower temperature settings. Lower mounting temperatures of 160ºF-175ºF lower the amount of adhesive absorption into paper art. The higher the temperature and the longer a project remains under the heat of a dry mount press the more saturation takes place.
As they heat up in a press, adhesives travel toward the heat source, generally the glass or platen in the top of the unit, and into the porous artwork. There will always be a certain percentage of removable adhesive which penetrates the back of the artwork, even with a removable tissue.
Even selecting a dry mount adhesive with the lowest melting temperature for the least amount of time (which in turn minimizes saturation), will not meet true conservation standards. In order for an adhesive to qualify as preservation it requires reversibility…or taking the art back to its original state.
Tissue Permanence or Removability
Removable adhesives bond after they reach temperature, are removed from the press and placed beneath a weight to cool. Once heated and removed, any mounting may then be tacked to a clean substrate with no new mounting tissue, placed back into a press, and the adhesive saturation alone will bond it quite well to the new surface. This will occur a number of times simply from adhesive absorption, and is the proper technique for maximum removal of all possible adhesive from an item that has been mounted and removed.
Though solvents may be optionally applied to the verso side of a project to remove remaining adhesive it could damage the inks or fibers and should be tested first. Also remember that introducing any new or foreign substances or chemicals is not a controlled conservation practice.
Another interesting observation concerning these studied archival-type tissues is that some appear to be removable while others are not. As noted above, removable tissues and films may be placed back into the press a little hotter a little longer and then peeled from the substrate for easy removal. Corona’s ConservaBond claims to mount as it reaches temperature, that makes it a permanent adhesive.
This product is a wonderful example of a permanent, porous, low temperature, tissue adhesive perfect for safe long term mounting that will not do any long term damage to its art. Where it goes wrong is when it claims preservation mounting is achieved when ‘archival quality’ substrates and mats are selected. Not totally true if it is indeed a permanent adhesive with absorption. Neutral pH, perhaps, conservation…not really.
Final Thoughts
Using heat-activated adhesives can never be considered archival because the very act of dry mounting art to a substrate breaks all conservation guidelines. Once the adhesive has saturated it can never be totally removed. Obviously RC photos don’t absorb adhesive because of the resin-coated layer on the bottom of the photo, but absorbent paper is another story.
If convincing yourself or your customers into believing the use of archivally named adhesives as a reasonable alternative to true conservation methods is almost as good, it isn’t. Will it hold things flat and not do damage to then, absolutely, but never sell it as an archival procedure. Always remember using the best products is the best idea regardless of the mounting method, just understand the terminology AND the limitations.
END
Copyright © 1998 Chris A Paschke
For more articles on mounting basics look under the mounting section in Articles by Subject.
Additional information on all types of mounting is found in:
The Mounting and Laminating Handbook, Second Edition, 2002,
The Mounting And Laminating Handbook, Third Edition, 2008 and
Creative Mounting, Wrapping, And Laminating, 2000 will teach you everything you need to know about getting the most from your dry mount equipment and materials as an innovative frame designer.
All books are available from Designs Ink Publishing through this website.
Chris A Paschke, CPF GCF
Designs Ink
Designs Ink Publishing
785 Tucker Road, Suite G-183
Tehachapi, CA 93561
P 661-821-2188
chris@designsinkart.com