An interesting article discussing linen backing, and some possible effects that adhesives can cause (to develop), including foxing.
Good article, John. 
http://www.ozefilm.com/linen-backed-movie-posters/
We discussed this article to death on the "other" forum. I actually shot off an e-mail to the Northeast Document Conservation Center and got a very nice response. They also provided a very nice article on storage...
from Charlie to NEDCC
Charlie said:
Hi,
We have had an interesting situation pop up in the Movie Poster hobby. A fellow collector had linenbacked posters from different restorers all stored in the same room and presumably the same humidity. Posters from a certain restorer exhibited foxing versus others after 10 years. It is common practice (some accept, some don't) to use wall paper paste, probably with antifungi. The collector is claiming that all the posters backed with wall paper paste are foxing free, while the ones that show foxing from the same restorer were backed with wheat paste. So we have two theories. Wheat Paste vs. Wall Paper Paste and this one restorer vs. all others. Many restorers use wheat paste in our hobby - I use it on my own projects. I am suspicious that a hygroscopic adhesive or chemical was used in the backing process that is accelerating the absorption of water from the air. Two questions. 1. Opinion on wall paper paste. 2. If there was an adhesive or chemical which could be causing the foxing, which would it be? What effect does microbes, from say storage or use of tap water, have once paper is dry and then rehumidified?
I would like to present your advice on our forum:
Pictures can be seen here:
Thanks in Advance,
Charlie.
Charlie,
These are all very good questions, however, with rather complex answers. Let’s begin with the storage environment.
High humidity, high temperature and excessive light levels will accelerate the deterioration process of all paper based artifacts. A high humidity environment would be in excess of 65% RH, and a temperature greater than 72 degrees Fahrenheit and at these levels mold can start to grow. Light exposure levels should be no greater than 20 foot-candles to prevent fading. Museum exhibition spaces are usually maintained at 10 foot-candles. In private homes or studios, maintaining ideal storage and exhibition environments is very difficult but these factors influence the material stability and help control mold formation. Technical information on environmental guidelines can be found on the NEDCC web site:
http://www.nedcc.org/free-resources/preservation-leaflets/2.-the-environment/2.1-temperature,-relative-humidity,-light,-and-air-quality-basic-guidelines-for-preservationIs commercial wallpaper paste better than wheat starch paste? The simple answer is “no.” Commercial wallpaper paste is usually proprietary so you do not know what is included in the formulation. The main component is usually a cellulose ether such as methyl cellulose. There may be unknown additives that may work just fine with contemporary wallpaper but not necessarily with paper base artifacts with redeeming value. Most commercial wallpaper pastes will have a fungicide incorporated in its mix. Any unknown additives with poor aging properties can cause paper to deteriorate and discolor so it is vital to know what is being used and how it will react with the paper, inks and colorants.
Conservation grade cellulose ethers and their equivalents go by names such as Methocel®, Ethulose®, Cellofas®, etc. We do know the composition and aging properties of these cellulose ethers and that is why they are used in the conservation profession. Cellulose ethers are less prone to develop mold than wheat starch paste but both types of adhesives are hygroscopic.
Wheat starch paste is a proven adhesive that has been used for centuries in Japan and China for mounting scrolls and creating screens. The aging properties are excellent and it is reversible, however, in a poor environment it can be a source of food for mold and insects. So the bottom line, using wheat starch paste and the formation of mold cannot and should not be a reflection on the quality of work of one restorer or conservator over another.
It is the obligation of the collector to properly house their collection in the best environment suitable for their artifacts and to protect the material.
What is foxing? Technically, foxing is referred to localized spot stains that develop from metal inclusions in the paper when it is first made. Hollander beaters were often the main source for small metal fragments that were cast along with the paper fibers to form the sheet. As the metal corrodes the corrosion products then stain the paper often a rust brown similar to a fox’s fur color.. The term foxing is often used interchangeably to also describe spot stains from mold.
Any moisture used during a treatment step, which by the way should only be performed by a trained individual, should be filtered, distilled or deionized to ensure there are no particulates, chlorine, soluble metals or organic material in the water that will result in any adverse reaction or deteriorate the object. Use of any poor quality repair materials, pressure sensitive tapes, non-reversible adhesives and improper repair techniques would be irresponsible.
If you require any additional information please let me know or you can visit our web site at
www.nedcc.org.
Thank you,
Michael
Michael K. Lee
Director of Paper and Photograph Conservation
Northeast Document Conservation Center
100 Brickstone Square
Andover, MA 01810
Phone: 978-470-1010
Fax: 978-475-6012
E-mail: mlee@nedcc.org
www.nedcc.org
