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LINEN BACKING MOVIE POSTERS – Wallpaper Paste or Wheat Paste?

By on September 9, 2014

My recent article warning about some of the potential problems with Linen Backing Movie posters drew a great deal of response which included a wide ranging reaction from collectors and restorers.

Firstly, let me say that I most certainly support the concept of linen backing movie posters. However, there are potential problems that can, and do occur and it would be foolish to ignore them. Twenty years ago, when the hobby was in its infancy, linen backers were few and far between. Today, there are a number of people who offer the service for restoration and linen backing movie posters.

I have done some more research since writing the article and have not changed my opinions, although I have certainly picked up more detailed knowledge. I think it is worthwhile sharing some of the information I have found.Linen Backing Movie Posters

It is fair to say that very few, if any, of the people or companies who offer services for linen backing movie posters have recognised tertiary qualifications as conservators or restorers. Many have picked up the techniques anecdotally or by trial and error and not by any sort of science based training. There is no doubt that standards vary and some are more talented, better qualified and more professional than others.

Linen backers do not always use the same materials or methods and the results can vary significantly. When I wrote the initial article, there was some discussion on a movie poster discussion forum  which included comments from Michael Lee. Michael is the Director of Paper and Photograph Conservation at the Northeast Document Conservation Center

This article focuses on the paste that is used by linen backers along with comments from Michael.

Wallpaper Paste or Wheat Paste for Linen Backing Movie Posters?

Wallpaper Paste

Some of the most prominent linen backers use premixed wallpaper paste that they purchase in bulk in drums. There are different brands of wallpaper paste with subtly different mixes – no doubt some better than others. Some of the ingredients are not disclosed as they are proprietry and the paste would possibly vary from one country to another. There are a number of reasons why some restorers use wallpaper paste:

  1. Practicality. The wallpaper paste comes premixed and this saves considerable time.
  2. Most wallpaper paste usually has a mould inhibiter which is obviously a benefit in reducing the likelihood of mould or foxing developing on a poster.
  3. Wallpaper paste is less likely to be a food source for insects as opposed to some wheat pastes which can attract insects.
  4. The mix is professionally controlled and mixed consistently as opposed to the potential of inconsistent and varying mixing of wheat paste by some linen backers.
  5. Clients who have movie posters linen backed generally want the cost kept as low as possible. The use of wallpaper paste helps reduce costs.

However, the use of wallpaper paste is not the preferred method for qualified conservators. According to Michael Lee:

“Wallpaper paste will contain a variety of ingredients that may adversely affect the cellulose in paper. Since many commercial wallpaper adhesive products are proprietary the conservator is reluctant to use a product with questionable aging properties and ingredients including preservatives that they are unfamiliar with. I would never risk applying wallpaper paste to an artifact valued at $25K or a woodblock print by Katsushika Hokusai.

Linen Backing Movie PostersThe other distinction is that wallpaper paste and wheat starch paste are two chemically different products. Most wallpaper pastes are made of cellulose ethers such as methyl cellulose. High grade, high purity methyl cellulose is regularly used by conservators as an adhesive. It has very different working properties than wheat starch paste. Again wheat starch paste adhesives are a modified starch which is very different from a cellulose ether based adhesive. All water based adhesives that are “reversible” with water will most likely have hygroscopic properties including commercial wallpaper paste.

I have used 4% methyl cellulose to mount period Zuber wallpaper in historic buildings. Methyl cellulose was chosen for its working properties and it is less likely to be a food source for insects and mold.”

One important point that I would make is that I have had linen backed posters stored for more than twenty years. I know that some of them were backed using wallpaper paste. Those posters show no signs of any deterioration or ageing at all.

It is a fact that some of the most well respected linen backers of movie posters use wallpaper paste. It would be interesting to hear their thoughts on the subject.

It should also be considered that many of the movie posters sold at major auctions have been linen backed using wallpaper paste. You can put any interpretation that you choose on that.

Wheat Paste

PSYCHO LINEN backed daybillIt can be misleading to simply say that a restorer uses “wheat paste”. An ad campaign in Australia some years ago had the slogan “Oils aint Oils” referring to the massive difference in grades of motor oils. The way in which wheat paste is mixed is also very important. According to Michael Lee …..

“Wheat starch paste just like “wallpaper paste” comes in a variety of grades. Conservators will always choose the highest quality wheat starch paste with the highest purity such as Aytex-P or Zin Shofu. Aytex-P is a highly refined, unmodified food grade product. That means it is strictly the wheat starch not wheat flour and there is no gluten, no additives, fillers or preservatives. Dried wheat starch paste adhesives will not grow mold once dry unless it is exposed to moisture or high humidity for an extended period of time. Conservators know what the aging properties are for quality wheat starch paste adhesives that is why we use it.”

Michael also made further comments on the forum about the way in which paste is mixed and applied:

“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.”

Some things to consider about the use of wheat paste:

  1. Which grade of wheat paste did the restorer use?
  2. Did the restorer mix the wheat paste correctly?
  3. Did the restorer use tap water or distilled water?

Ideally, posters backed with a high quality wheat paste using “Best Practice” methods would be the way to go. However, you cannot be certain that all linen backers of movie posters to use best practice materials and methods.

Should linen backers disclose which paste they use?

This is certainly something worth considering. However, I do know of one linen backer at least who would not consider doing this. His policy is that he uses his own paste and the “formula is proprietary”. However, I am aware that he purchases drums of wallpaper paste and adds a small ingredient to the mix which, he feels, entitles him to say that he uses his own mix of paste.

My opinion

Linen Backing Movie PostersIn a “best practice” scenario and from a conservation point of view, I believe that a high quality wheat paste would be more desirable than using wallpaper paste. The purist professional conservator would frown on using wallpaper paste in linen backing movie posters.

However, from a purely personal point of view, I believe that there is less likely to be problems with posters that have been backed using wallpaper paste, particularly based on the fact that some linen backers of movie posters have different skill sets, qualifications, standards and methods.

Speaking purely as a customer looking to get posters linen backed, I would probably feel more comfortable retaining the services of someone who used wallpaper paste rather than wheat paste, bearing in mind the mould inhibitor in wallpaper paste and the fact that it is less likely to attract insects.

I would not be entirely confident in someone who used a wheat paste mix unless they had very strong conservation credentials. This is based on my experiences of finding that movie posters that were backed by restorers who used a form of wheat paste have deteriorated over time.

However, I am sure that some of the qualified linen backers who use high grade wheat paste do exceptional work. I guess the most important thing is to try to find a highly competent linen backer who has experience and the necessary credentials to do a good job. They are not always easy to find.

Who is at fault when problems occur?

Linen Backing Movie PostersMy previous article on linen backing highlighted posters that I had linen backed some years ago that have developed severe foxing and have been basically ruined. The cost of re backing the posters will be somewhere in the region of $15,000.00. I am not the only one to have experienced problems with linen backed posters deteriorating over time.

The excuse has often been “You must have stored the posters in a humid environment that has attracted mould” or “You live in a humid climate”.

If they are saying that living in a humid climate is a problem for storing linen backed movie posters then that would exclude half the world’s population from getting their posters backed.

It is easy to say that it is the customers fault. It is interesting that I have never heard of any linen backer providing a disclaimer or notice advising how posters should be stored.

However, there is no doubt that humid conditions can encourage the growth of mould and it is always going to be very difficult to determine exactly how and why some linen backed posters might have deteriorated or developed foxing issues. I can only say that my posters are all stored in a very cool dry environment. Other posters stored over a similar time frame have not developed mould or foxing and remain in the same condition as  the day they were backed.

I asked Michael Lee about storing linen backed posters:

“Good preservation practices always start with the proper storage environment whether it is in the home, museum or historical society. Guidelines for proper storage follow;  http://www.conservation-us.org/about-conservation/caring-for-your-treasures/paper#.VAXcl2MmXHQ

Linen Backing Movie Posters If damage occurs after treatment and while in a proper environment then that is usually an indication that poor quality or contaminated materials were used during treatment. The offending contaminants could even have originated from the linen depending on the manufacturer.

Foxing is technically localized spot stains that develop from metal inclusions in the paper during the manufacture of the paper. As the metal inclusions corrode they create rust stains. The term is often used interchangeably to include spot stains from mold. If an object is treated aqueously with unfiltered water (tap water) that contains metal particulates or even soluble metals then the potential for foxing to occur is high. Water used to mix adhesives or perform treatment steps must be filtered to remove particulates, soluble metals, organic contaminants, chlorine and not be overly boosted to a pH above 8.5.

The foxing spots that occurred on your posters post-treatment most likely originated from contaminants in either the water or the linen. Properly made wheat starch paste adhesive will not on its own result in foxing spots after it has dried completely and has remained dry.”

I am reasonably convinced that the restorer used inferior quality materials resulting in the damage to my posters over a long period of time but that is only my opinion. I cannot be absolutely certain of the cause of the foxing.

Standards for Conservators and Restorers

Linen Backing Movie PostersMichael Lee provided some information ….

  1. Restorers and conservators are all human. There are very good restorers and conservators and there are average to poor restorers and conservators.
  2. In the “Conservation Profession” we draw a distinction between restorer and conservator. The conservator is required to abide by a code of ethics and standard of practice. The core document on the code of ethics from the American Institute for Conservation (AIC) are contained in the following link, http://www.conservation-us.org/about-us/core-documents/code-of-ethics#.VAXGjGMmXHQ
  3. In some countries, conservators are vetted and/or certified by their peers and associated professional organizations. The following is from the AIC Q&A web page.
  4. How do I know the conservators listed are qualified?

The only conservators listed in Find a Conservator are Professional Associates and Fellows of AIC. The minimum requirements for a Professional Associate are two years of professional conservation experience and an undergraduate degree. The minimum requirements for a Fellow are ten years of professional experience and at least three years of graduate-level education in a conservation-related field. Additionally, applicants to both categories must be approved by a panel of their peers.

  1. Conservators are required to use time tested and scientifically tested materials with good aging properties; http://www.conservation-us.org/about-us/core-documents/commentaries-to-the-guidelines-for-practice/22#.VAXJpmMmXHQ
  2. Many conservation materials used on paper based artifacts must also pass the photo activity test (PAT) for use with photographic materials to prevent fading or any other adverse chemical reaction. PAT approved materials are all scientifically tested by the Image Permanence Institute.

I am not sure if these standards apply to linen backers of movie posters or not but maybe it would be worth developing a set of standards for all linen backers of movie posters to adhere to.

I hope this article helps in shedding some light on linen backing movie posters. When choosing a linen backer you should not necessarily base your choice on the lowest price but be mindful that some backers are much more skilled than others and consider their qualifications and the materials that they use.

About John Reid

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