The Home Archivist – Dust, Mold, and Adhesives, Part II

      1 Comment on The Home Archivist – Dust, Mold, and Adhesives, Part II

Home-Archivist-300x170 2By Jessica Dunkin

In the last post, I introduced readers of the Home Archivist to two institutions committed to the preservation of Canada’s documentary heritage, Library and Archives Canada’s (LAC) Preservation Centre and the Canadian Conservation Institute (CCI), and two professionals at work in the field of paper conservation, Doris St-Jacques and Greg Hill. I also provided readers with a list of safety equipment and tools that paper conservators use to process historical documents. In part two, we will explore how conservation professionals put those tools to use when they encounter paper documents affected by dust, mold, soot, adhesives, and other accretions.

Greg and Jess 127737-0006

Conservator Greg Hill and Author Jessica Dunkin at the Canadian Conservation Institute {Photo Credit: © Government of Canada, Canadian Conservation Institute, CCI 127737-0006}

A quick disclaimer, these posts are not intended as an instruction manual for the home conservator, but rather to increase public awareness of heritage conservation and to demonstrate the technical skill required to perform conservation treatments on paper. LAC and CCI have specialized facilities designed for the conservation and preservation of a wide range of archival materials. No home laboratory, however well equipped, can stand in for these kinds of facilities. Nor can a blog post replace the training and technical expertise of a professional conservator, especially when dealing with potentially hazardous substances like mold and animal accretions or performing delicate work like tear repair. To locate a conservator in Canada, please contact the Canadian Association of Professional Conservators (CAPC).

*     *     *     *     *

Before turning our attention to treatment options for the MacKendrick letters, I want to pause briefly to consider three guiding principles in the field of heritage conservation. Recognizing that historically some treatment practices and materials have been damaging to documents and artifacts, and that current practices may also prove to be harmful, conservators should only perform treatments that are reversible. They should also adhere to the principle of minimal intervention, which, to borrow from the Saskatchewan Heritage Foundation, “means to do as much as necessary and as little as possible.” The objective here is to preserve the document for future users without compromising the integrity of the original. For paper documents, some cleaning, typically surface cleaning, is advisable to improve readability. It may also be necessary to remove substances such as dust, soot, and adhesives that hasten deterioration.

Work on archival documents should take place in a well-ventilated space. Most institutional laboratories are equipped with sophisticated ventilation and exhaust systems, and have fume hoods and mold cabinets. Properly worn particulate respirators and gloves, used only once to avoid the transfer of contaminants, provide additional protection, especially when working with documents that are particularly dirty or affected by mold.

Fume Hood

Fume Hood, Duke University

Conservation work should be performed on a large flat surface, ideally covered with large sheets of white paper that can be changed frequently. Greg stages his work, so that different parts of the treatment process happen in different locations, thereby keeping the documents clean and, in the case of moldy items, preventing cross contamination and re-molding. Conservators often have a camera handy while they work, so they can document the items before, during, and after treatments. CCI has in-house photographers for this very purpose.

You’ll recall that I brought two bundles of letters from the MacKendrick collection with me when I met with Doris and Greg, as well as a two loose letters. The conservation treatments these letters received orient the following discussion.

Caption: The Letters (Photo Credit: © Government of Canada, Canadian Conservation Institute, CCI 127737-0001 and Jessica Dunkin)

The Letters (Photo Credit: © Government of Canada, Canadian Conservation Institute, CCI 127737-0001 )

Dirt and Dust

Dirt and dust, you may recall from an earlier post, are abrasives. Dust can also attract moisture, which encourages mold growth. Thus, dirty paper documents should be thoroughly cleaned before they are organized and re-stored.

We began by cleaning the exterior of the bundle, to avoid mess during later stages of the work. With the exposed surfaces of the stack clean, we used scissors to cut the string holding the bundle together. (Unless this material will be of interest to an archivist or historian, there is no need to keep it.) We then turned our attention to cleaning individual letters, starting with the front and back of the first envelope. When the outside was clean, we removed the letter in order to attend to the envelope’s insides; dust and dirt from within will eventually find its way into the folder where the letters and envelopes will be stored. With the envelope complete, we cleaned each individual page of the letter, taking special care because folds are often brittle (see below for a discussion of flattening letters).

A vacuum is ideal for removing larger particles of dirt and dust. Doris vacuums on an angle to reduce the suction power of the vacuum and the potential damage to a document. If she encounters a particularly fragile item, she places a square of plastic screen over the document to protect it while she works.

A soft paintbrush is an alternative to a vacuum. Greg demonstrated how to brush from the centre of the envelope to the edges. This protects the edges, which are often the most fragile and vulnerable to damage during treatments. If the conservator encounters a tear, they brush with the grain of the tear, so as to not exacerbate the damage. Brushes that are flat and of medium width with lightly coloured bristles (to indicate when the brush is dirty) are best for this purpose. A clean piece of fabric or a blotting paper can be used to remove dirt from the brushes.


(Photo Credit: Jessica Dunkin)

Greg and Doris use different paintbrushes and sponges depending on the nature of the surface dirt. A soft brush does the least surface damage and works well for materials with loose dust. Stiffer brushes should only be used if mud is caked onto the document and needs to be dislodged. Sponges remove residues that would otherwise smear. If the paper is fragile or has a soft surface, cleaning may be limited to light dusting with a soft brush.


Because the MacKendrick collection survived a fire, a number of the letters are covered with soot. Soot is carbon black, a stable compound which on its own will not harm a paper document. It is, however, hydroscopic, meaning it absorbs moisture, and oily (read: messy). Dry sponges (Absorene or a make-up sponge) are good for removing soot. Doris demonstrated how to gently dab at the affected area in small concentric circles. She used different corners of the sponge as it became dirty to avoid smearing.


(Photo Credit: Jessica Dunkin)


To the trained eye, mold is easily recognized, less so to the layperson. Neither Doris nor Greg identified mold on the letters that I brought to them, a relief given the health risks associated with mold exposure. Mold can exacerbate existing health conditions such as asthma and allergies. Some species of mold contain mycotoxins, which can cause rashes, dizziness, immunosuppression, and cancer. CCI has produced a technical bulletin on mold that readers may find useful.

Conservators at both institutions conduct mold treatments in a mold cabinet outfitted with a HEPA filter. The cabinet does the work of containing the mold, so a N95 particulate mask is sufficient. If a mold cabinet or fume hood is not available, the conservator wears a respirator with a HEPA filter (3M N100 filter).

If you discover mold on documents, seal the affected item(s) in a bag and place the bag in a freezer for a minimum of 48 hours. Sub-zero temperatures do not kill mold. They do, however, render it inactive, which prevents it from spreading. This will give you time to arrange for treatment.

Because of the potential health risks, Doris advises readers of The Home Archivist to have a professional conservator treat all documents affected by mold. Greg, on the other hand, is of the opinion that if there is only a very small amount of mold, the work can be undertaken by a lay person provided they wear the appropriate safety equipment (gloves and a mask with a HEPA filter) and perform the work outside in a well-ventilated area away from building air intakes. Tools used for mold treatments, including the vacuum, must be sanitized afterwards to avoid cross-contamination.

Animal Accretions

Letters 2

Photo Credit: Jessica Dunkin

One of the stacks that I brought with me had what looked like the remnants of a mouse nest or mouse vomit on the top of the stack. Work with these documents should be undertaken in a well-ventilated space wearing a N100 respirator because of the potential health risks. As with other hardened deposits, animal accretions are best removed bit by bit with a metal microspatula. Using a fine paintbrush or a Q-tip that has been dipped in water and blotted, we introduced a small amount of moisture to a part of the affected area. This softened the deposit, making it easier to remove with the spatula.

As we will see, moisture is an important tool for conservators. However, too much will do more harm than good. Water should always be used sparingly and with caution.

Stuck Letters

On a handful of occasions, I discovered letters in the MacKendrick collection that were stuck inside of their envelopes. These letters can be steamed to loosen the adhesive or accretion that is preventing the letter’s removal. However, this has the potential to damage the paper and the surface media. Alternatively, a small amount of moisture can be introduced to the affected area with a paintbrush or Q-tip, and a micro-spatula used to gently coax the pages apart. It is best to do this a bit at a time and to place something, a Teflon spatula for example, between the affected sections so they don’t re-attach.

Flattening Letters

Paper, Greg informed me, has incredible memory. It long remembers folds, creases, and curls. Relaxing and flattening are common conservation treatments to make paper documents consultable. According to Doris, my practice of dry flattening the MacKendrick letters using folders and the Catholic Encyclopaedia, while not ideal or particularly effective, did not damage the items because of the relatively good condition of the paper.

Humidifying documents is a more effective treatment because it relaxes the paper, making it more supple and able to be manipulated. It also reduces the potential for damage; the drier the paper, the more brittle it is. Humidification should be avoided for heavily coated paper, parchment, vellum, and materials with highly soluble inks, pigments, or other colours. It should only be undertaken after a document has been cleaned. Otherwise, surface dirt can become permanently ingrained in the paper fibres, or it can turn to mud, rendering the document more difficult, if not impossible to clean in the future.

Paper documents that are in good condition can be flattened with minimal effort. At LAC, conservators use large mat boards for this task. The mat boards are lightly misted with water (too much water can damage the letters and disfigure the boards). The documents are then spread in a single layer over the board and a second board is placed on top. The process is repeated in multiple layers until there is a good stack of document-covered boards that can be weighted. You can see an example here.

One of the MacKendrick letters that I brought with me was rolled up and a little squished. It was also more fragile than the others. This letter needed to be humidified in order to be unfolded. Before a conservator humidifies a document, they test the surface materials using a tiny amount of water on a small section of the writing. My rolled-up letter was written in graphite pencil, so humidification could proceed. If the author had used a copying pencil, which are made of methyl-violet, exposure to humidity may have turned the writing purple.

In the lab, humidification work is undertaken in a humidification chamber. I tried to approximate this chamber at home using this article as a guide. I found two cake tins, one smaller than the other. I put a small amount of warm water in the larger of the two pans before resting the smaller tin inside it. I placed the letter in the inner pan, taking care to not let it come into contact with the water, and covered the whole contraption with plastic wrap. The process can take up to several hours. Keep an eye open for condensation forming on the plastic wrap.

Humidification Chamber

DIY Humidification Chamber (Photo Credit: Jessica Dunkin)

For those wanting more information on humidifying and flattening paper, this article may be useful.


Repairing tears, like treating mold, is work best reserved for a professional conservator. Most of the tear treatment products available through archival suppliers like University Products and Carr MacLean do more harm than good. To keep a document with tears consultable, Doris suggested making a photocopy or placing the document in a clear mylar (polyester) sleeve. Greg advised against vinyl sleeves (typically labelled PVC) because vinyl is a less stable plastic.

I want to thank Greg and Doris for taking the time to share their knowledge and technical skills with me. I learned so much during our meetings and came away with a renewed enthusiasm about my work with the MacKendrick letters. In the next post, I will discuss theories and practices of archival management with an eye to creating an organizational system for the collection.


Jessica Dunkin is a SSHRC Postdoctoral Fellow in the School of Kinesiology and Health Studies at Queen’s University. Her doctoral dissertation, “Canoes and Canvas: The Social and Spatial Politics of Sport/Leisure in Late Nineteenth Century North America” (Carleton University, 2012), explored the annual encampments and regattas of the ACA from 1880 to 1910. In addition to working with the MacKendrick letters, Jessica is researching physical activity programming for urban working-class women in Canada in the decades around the turn of the twentieth century. You can follow her on Twitter at @dunkin_jess.


Creative Commons Licence
This work is licensed under a Creative Commons Attribution-NoDerivatives 4.0 International License. Blog posts published before October  28, 2018 are licensed with a Creative Commons Attribution-NonCommercial-ShareAlike 2.5 Canada License.

Please note: encourages comment and constructive discussion of our articles. We reserve the right to delete comments submitted under aliases, or that contain spam, harassment, or attacks on an individual.