Archival Terms and Definitions for Preservation of Documents, Photos, and Paper Collections

Understanding Key Preservation Terms

If you're trying to keep books, documents, photos, or other old items in good shape, you need to know what you're working with. This guide breaks down common archival terms in plain English. You don’t need a background in conservation to understand this. Whether you're protecting family records or building a personal archive, the terms below will help you choose the right materials and avoid the ones that can cause damage.

 

A

What Is Acid and Why It Matters in Preservation

Acid is a chemical that forms hydrogen ions when mixed with water. You don’t have to understand the science deeply, but here’s what matters: acid eats away at paper, cardboard, cloth, and other materials made from cellulose. It breaks them down, makes them brittle, and shortens their lifespan.

Acid can get into materials in different ways. Sometimes it’s there from the start because cheap or poor-quality ingredients were used. Other times, it spreads from nearby materials that contain acid. It can also come from pollution in the air. Acid doesn’t always stay where it starts. It moves. That’s where acid migration comes in, and that’s a problem too.

What Acid-Free Actually Means

When something is labeled acid-free, it means the material has a pH of 7.0 or higher. That sounds scientific, but just think of it as meaning it doesn't have active acid that will eat away at paper or photos.

People often confuse acid-free with buffered or alkaline, but those aren’t the same thing. A material can be acid-free without being alkaline. And being alkaline means it has something added to fight off acid over time.

Even if a product is acid-free when it's made, that doesn’t mean it will stay that way forever. Chemicals used in the making process, like chlorine for bleaching or aluminum in sizing, can leave traces that react later. Plus, pollution in the air can lead to acid forming again unless something in the material fights it off. That’s why buffering with an alkaline compound is important for long-term storage.

What Acid Migration Means for Your Collection

Acid migration is when acid moves from one material to another. It happens when acidic materials are touching something that isn’t acidic.

For example, let’s say you put a clean document inside an old box or wrap it in cheap packing paper. If those materials are acidic, the acid can spread into your document and damage it.

This process happens slowly, but the damage adds up. That’s why even the containers and folders you use to store things matter. You want to avoid anything that might carry acid.

Understanding this helps you avoid using materials that quietly destroy the very things you're trying to protect.

Acrylic in Archival Use

Acrylic is a type of plastic that's strong, clear, and long-lasting. It’s lightweight, holds up well outdoors, and doesn’t fade or change color when exposed to light. These features make it useful for many things, but in preservation work, its real value comes from how stable it is.

Unlike some other plastics, acrylic doesn't break down or give off harmful chemicals over time. That matters when you're using it to protect things like artwork, documents, or photos. You don’t want the container or frame causing damage.

Acrylic comes in different forms. You can get it as solid sheets, thin films, or as part of resin-based adhesives. Sheets are often used in display cases and picture frames because they let you see the item clearly while keeping dust and pollutants out. Films may be used to line boxes or wrap fragile items. Acrylic adhesives are used when items need to be fixed or sealed without adding moisture or harmful chemicals.

If you're looking for a safe, clear, and stable material to use around sensitive items, acrylic is usually a smart choice. But not all plastics are safe, so knowing you're using acrylic makes a difference.

Why Alkaline Materials Are Important for Preservation

Alkaline materials have a pH level above 7.0. This might sound technical, but the takeaway is simple: alkaline substances help protect things from acid damage. They can either neutralize acid that’s already there or stand by as a buffer to fight off acid that might form later.

Buffers are chemical compounds added to paper, board, or other materials to hold off future acid formation. The most common ones are magnesium carbonate and calcium carbonate. These are often added during manufacturing or during a special process called deacidification, which treats old paper to make it last longer.

When you see that a paper or storage material is buffered, it usually means it contains one of these compounds. This gives the material an extra layer of defense, especially in areas with pollution or when the item might come in contact with acidic materials.

Using alkaline-buffered products is a key way to keep archives, records, and collections from breaking down over time.

Alpha Cellulose and Its Role in Longevity

Alpha cellulose is a pure form of cellulose that comes from cotton. This matters in preservation because paper made from alpha cellulose tends to last longer than paper made from wood pulp or lower-grade fibers.

Cellulose is the main building block of most paper. But not all cellulose is the same. Alpha cellulose is the most stable kind. It's strong, doesn't break down easily, and doesn’t carry the extra chemicals found in regular wood pulp.

When you see paper or board made with a high percentage of alpha cellulose, it usually means it’s a better choice for long-term use. It won’t yellow or fall apart as quickly.

Cheaper paper includes other parts of the wood that cause it to weaken faster. So if you're storing something important, look for paper products that mention alpha cellulose. It’s one of the best indicators that the material will hold up over time.

What “Archival” or “Archival Quality” Really Means

The term “archival” or “archival quality” gets used a lot, but it’s not an official standard. It’s more of a general idea. It suggests that the material is safe to use for long-term storage and won’t damage the items it touches.

When a material is called archival, it usually means it's durable, chemically stable, and doesn’t contain things like acid or harmful additives. That includes paper, boxes, adhesives, and plastics. But here's the problem: the word itself doesn't tell you exactly how long it will last. No rules or tests back up the term. So while "archival quality" is a helpful sign, it’s not a guarantee.

If you're serious about preservation, look past the label. Check the details. Make sure the material is acid-free, lignin-free, and buffered when needed. Look for materials made with alpha cellulose or tested for long-term stability.

The word archival can guide you, but it shouldn't be the only thing you rely on. Always read the full description when choosing products for storing or protecting valuable items.

 

B

What Basis Weight Means and Why It Matters

Basis weight tells you how heavy a type of paper is. It’s based on the weight of 500 full-sized sheets of that paper, measured in pounds. But not all paper is cut the same size, so the base size depends on the type of paper being measured.

This is important when you're picking paper for storage, printing, or preservation. Heavier papers are usually thicker and stronger. They’re better for long-term storage because they don’t bend, tear, or wear out as easily. Lighter paper can be useful too, especially for things like interleaving sheets or separating documents inside folders, but it’s not always sturdy enough to protect delicate items on its own.

When looking for preservation-grade paper, don’t just go by feel. Look at the basis weight. It helps you understand how the paper will hold up over time, especially when it comes to storing fragile documents, rare prints, or historic photos.

Understanding What Board Means in Archival Use

When people in preservation talk about board, they usually mean two kinds: fiberboard and solid board. Both are thicker and stronger than regular paper or cardstock. They’re used to make archival boxes, backing boards, folders, and other storage supplies that need to be sturdy and long-lasting.

Fiberboard is often made by compressing fibers together into a thick sheet. Solid board is more uniform and made from a single material. Both types can be found in acid-free and buffered forms, which is what you want for archival purposes.

The key thing to remember is that not all boards are safe for preservation. Regular cardboard, like what you see in shipping boxes or cheap folders, often contains acid and breaks down fast. Always choose archival-quality board when you're protecting collections. It keeps items flat, blocks light, and guards against bending and wear.

What Buffering Is and When It Matters

Buffering is a method used in archival paper and board to slow down acid damage. A buffering agent is added to the material during manufacturing. Calcium carbonate is the most common one used. Its job is to neutralize acids that come from pollution, other materials, or even from the stored item itself.

Buffered materials create a stable environment for books, papers, and most photos. The buffer acts like a shield, keeping acid from breaking down the cellulose fibers in the material. This helps prevent brittleness and decay.

But buffering isn’t always safe for everything. Some items, especially those made from natural animal materials like wool, silk, or leather, can be sensitive to the chemicals used in buffering. In those cases, unbuffered materials are better. The same goes for certain historic or rare photo processes like dye transfer prints or cyanotypes. These are delicate and can react badly to buffered enclosures.

One thing to keep in mind: unbuffered materials don’t block acid. In fact, they can soak it up from the air or from other items nearby. Over time, they might become acidic themselves. That’s why it’s important to match the storage material to the item you’re trying to protect. Use buffered materials for most things unless you’re working with sensitive textiles or specialty photographs. Then, unbuffered is the safer choice.

Knowing the difference between buffered and unbuffered materials helps you avoid mistakes that can lead to long-term damage. Choosing the right one can protect your collection for decades instead of years.

 

C

Calcium Carbonate: A Critical Buffer Against Acid

Calcium carbonate is one of the most trusted materials used in preserving paper-based items. It's a naturally occurring compound that acts as a buffer. This means it helps neutralize acid, which is one of the biggest threats to paper, photographs, and fabric artifacts.

During the paper-making process, calcium carbonate is often added directly into the pulp. When it's included at that stage, the finished paper has a built-in defense against acid. This buffering agent keeps the paper from breaking down as fast when exposed to environmental pollutants, aging, or other acidic materials.

In archival storage, you'll also find calcium carbonate in folders, boxes, sleeves, and other containers. Its job there is the same: to block acids from forming or spreading. So even if acid enters the environment later (from pollution, nearby objects, or human handling), calcium carbonate can slow down or stop the damage.

This compound doesn’t just protect items from their own internal chemical decay, it guards them from the outside world. That’s why it’s considered essential for long-term preservation.

Caliper: Measuring Paper Thickness the Right Way

When it comes to paper, not all sheets are equal. One key detail is thickness. That’s where caliper comes in. Caliper is a unit used to measure how thick a piece of paper or board is. It’s measured in points, and each point equals one one-thousandth of an inch.

So, if a sheet has a caliper of 10 points, it's 0.010 inches thick. This matters in preservation because the thickness of storage materials like folders, boxes, and interleaving sheets affects both protection and space.

Thicker paper can offer more protection, but it also takes up more room and might not be flexible. Thinner materials save space but might not shield fragile items from pressure, light, or handling. Knowing the caliper helps you choose the right material for what you're storing.

Archivists rely on caliper measurements to get the balance right between durability and fit. That’s why it's a key part of preservation planning.

Cellulose: The Foundation of Paper and Plant-Based Materials

Cellulose is a natural compound found in the walls of plant cells. It's what gives plants their structure. When it comes to preservation, cellulose matters because it’s the main ingredient in paper, cardboard, and even some textiles.

Any product made from wood, cotton, or other plant fibers will have cellulose in it. High-quality paper used in archives often comes from purified cellulose sources, especially cotton, because it lasts longer and breaks down slower than paper made from wood pulp.

But cellulose is sensitive to its surroundings. Over time, it can break down, especially in the presence of acid, heat, light, or pollution. That breakdown leads to brittleness, yellowing, and weakness.

To keep cellulose-based materials stable, it’s important to control the environment they’re stored in. Use acid-free containers, avoid direct light, and keep humidity low. Understanding what cellulose is helps explain why so much care goes into choosing archival materials.

Chemical Stability: A Material’s Resistance to Change

Chemical stability means a material doesn't react easily to other substances. It doesn’t fall apart or change when exposed to light, oxygen, or pollution. That’s exactly what you want when storing something for the long haul.

Materials with high chemical stability don’t degrade quickly. They stay intact even after years of use or storage. In preservation, this trait is vital. It helps protect books, photos, papers, and textiles from becoming brittle, discolored, or crumbly.

When archivists choose folders, boxes, or sleeves, they look for ones made from chemically stable materials. These are sometimes described as inert or stable, meaning they won’t react with whatever they’re in contact with.

Stable materials are the opposite of reactive ones. They’re safe for storing delicate items because they don’t speed up the decay process. That’s why chemical stability is a top requirement for anything that comes in direct contact with your collection.

Conservation: The Work of Keeping Original Materials Intact

Conservation is about actively taking care of valuable items so they last longer. It’s the hands-on process of repairing, cleaning, and stabilizing things like old books, artworks, museum pieces, or historical documents.

Unlike simple storage or basic care, conservation often involves direct treatment. This could mean flattening warped paper, mending torn pages, or deacidifying brittle materials. The goal is to make sure the original object survives, not to replace or recreate it.

Conservation work is guided by a respect for the item’s history. The goal is always to keep as much of the original material and structure as possible. That’s why conservators use materials and methods that don’t harm the object and can be reversed if needed.

This work plays a major role in museums, archives, and libraries. But even private collectors benefit from understanding what conservation is and when it's needed. If something is falling apart, you have to stabilize it so it can continue to exist in its original form.

 

D

What Deacidification Really Does for Paper Preservation

Deacidification is a chemical process used to stop acid from breaking down paper. Over time, paper made from wood pulp or poor-quality materials becomes acidic. This makes it turn yellow, grow fragile, and eventually fall apart. Deacidification slows that down. It works by neutralizing the acid that's already inside the paper. Then, it leaves behind an alkaline substance that acts like a buffer, which helps guard against new acid forming later.

This process is mostly used on books, documents, newspapers, and other paper items at risk of acid damage. It’s especially important for older items made before acid-free paper became common.

But while deacidification helps stop further damage, it doesn't reverse what's already been done. If the paper is already brittle, dry, or falling apart, this treatment won’t make it strong again. It won't bring back flexibility, either. Think of it as hitting pause on the decay, not rewinding it.

There are different methods for deacidifying materials. Some are done by hand with sprays or baths, and others are done in bulk using machines, especially in libraries or archives. The goal is the same: keep the acid from eating away at the paper any further.

 

E

How Encapsulation Protects Flat Objects Like Paper and Photos

Encapsulation is a way to protect flat materials like documents, posters, or photos without gluing or mounting them. It involves sealing the item between two sheets of clear polyester film. The edges are sealed shut, which creates a barrier between the item and the outside air. This shields it from dirt, moisture, and physical wear.

Encapsulation works well for fragile items that are at risk of tearing or breaking during handling. Since the item isn’t glued down, it stays loose inside the plastic. That means you can always open the seal later and remove the item without damage. You just cut open the edge of the film.

It’s important to know that encapsulation doesn’t fix problems like acid damage. If the paper or photo inside wasn’t deacidified before sealing, it can keep getting worse over time, even inside the plastic. The polyester film protects the outside, but it doesn’t stop internal decay. That’s why proper prep is key. Deacidify first, then encapsulate.

This method is often used in archives, libraries, and museums to safely display or store fragile items while still keeping them accessible. It's simple, reversible, and non-invasive, which makes it a good option for materials that need extra care.

 

F

What Fiber Content Means and Why It Matters

Fiber content tells you what a material is made from. When you look at a sheet of paper, a folder, a box, or even book cloth, you're seeing a mix of fibers that were pressed and treated during manufacturing. The fiber content is usually listed as a percentage, and it shows what kinds of fibers were used and in what amounts.

This isn’t just technical detail. The type of fiber in a material directly affects how long it lasts and how well it holds up to age, light, heat, and moisture. It also affects whether the material stays chemically stable or breaks down over time.

Archival-quality materials usually use high-grade fibers like cotton, linen, or purified wood pulp. Cotton is especially favored because it’s strong, naturally acid-free, and doesn’t get brittle as quickly. It’s often referred to as “rag content.” Paper or board with 100% cotton fiber content is very durable and is considered a top choice for storing valuable or irreplaceable items.

On the other hand, materials made from low-grade or unrefined wood pulp may contain lignin, a substance that breaks down and becomes acidic over time. Lignin can also darken the paper and speed up its deterioration. That’s why cheap office paper or cardboard is not a good choice for long-term storage, even if it feels sturdy at first.

Knowing the fiber content gives you a clearer picture of what you're working with. It’s not just about feel or thickness. You need to know what’s inside the material if you want to trust it with your collection.

What Fiberboard Is and How It’s Used

Fiberboard is a thick, sturdy type of paperboard. It’s made by pressing layers of dense fiber sheets together under high pressure. This process creates a tough, heavy material that holds its shape and resists bending.

You’ll often see fiberboard used in storage boxes, conservation enclosures, and book covers. It can take a lot of wear and tear, which makes it good for protecting fragile contents. But not all fiberboard is created equal. Some types are made with poor-quality fibers or harmful adhesives that give off acids or other pollutants over time.

For archival use, you want fiberboard that is acid-free and, ideally, buffered. That means it won’t introduce acid into your storage environment, and it has an extra layer of protection against airborne pollutants and acid migration.

If you’re storing rare books, manuscripts, prints, or photos, using the wrong kind of fiberboard can slowly damage what’s inside, even if everything looks fine on the surface. That’s why it’s worth checking how the fiberboard was made and what kind of fibers it contains.

Choose materials labeled specifically for archival or museum use. These are made with stable fibers and are processed in a way that prevents acid from forming later. That extra step matters when you're aiming to preserve something for years, decades, or generations.

 

G

Grain Direction in Paper and Why It Affects Preservation

Grain direction refers to the way the fibers in a sheet of paper line up during the manufacturing process. When paper is made, pulp flows in one direction on the machine. As it dries, the fibers settle mostly along that flow. That direction becomes the "grain" of the paper.

This matters more than most people think. Paper reacts differently depending on how you fold, store, or handle it in relation to the grain. It folds more cleanly and strongly when you fold along the grain. That’s called folding "with the grain." If you fold against it, the crease may crack or the fibers might tear unevenly. You’ll feel more resistance when trying to fold across the grain.

Paper can be labeled as long grain or short grain. That has to do with which edge the fibers run parallel to. If the fibers run along the longer side of the sheet, it’s long grain. If they run along the shorter side, it’s short grain. Knowing this helps you decide how to store or cut sheets, especially if you're binding books or making folders for storage.

Choosing the right grain direction becomes essential in archival work. It impacts how stable a box or folder stays over time. It also affects whether pages lie flat or curl. When preserving fragile materials, the last thing you want is added stress from folding or storing paper the wrong way. Always match grain direction to your intended use. It saves trouble and extends the life of what you’re trying to protect.

 

I

Inert Materials and Chemical Stability in Preservation

The term "inert" describes something that does not chemically react with other substances. In the world of preservation, this is a big deal. You want the containers, sleeves, and display supports you use to be chemically stable. That means they won't break down over time or release gases that could harm paper, photos, textiles, or film.

An inert material won’t interact with the item it touches. That’s why archivists use polyester, polypropylene, or polyethylene for storing things like photographs or documents. These plastics are known for being chemically neutral. They don’t release acid, and they don’t trap moisture. They just sit there and do their job without affecting the object.

When you see "inert" on a supply list, think of it as a safe zone. The point is to avoid materials that change over time or cause damage slowly. Some plastics, foams, or coated papers can seem fine at first, but they break down and give off harmful byproducts as they age. Inert materials avoid that risk.

Using chemically stable, inert products is one of the best ways to keep your collection safe for the long haul. It’s not just about what looks clean or sturdy. It’s about what will stay harmless over decades. That’s the real goal in archival storage.

 

L

Lignin and Why Lignin-Free Paper Matters for Preservation

Lignin is a natural compound found in plants. It's what gives trees and other woody plants their strength and stiffness. Without lignin, stems and trunks wouldn’t be able to stand upright. So, in nature, lignin serves a clear purpose. But in the world of paper and preservation, lignin causes problems.

When paper is made from wood pulp, lignin is usually part of the mix unless it’s been taken out. Over time, lignin reacts with light, heat, and oxygen. This reaction causes paper to darken, yellow, or turn brittle. You’ve probably seen this before in old newspapers. They age quickly because they’re full of lignin. They lose color, break down, and crumble because lignin speeds up the decay process.

That’s why many archival and conservation experts prefer lignin-free paper for storing important documents, photographs, or books. When paper is made without lignin, or when most of it is removed, it holds up better over time. It stays whiter, more stable, and less likely to crack or fall apart.

Lignin-free paper usually goes through extra processing to remove as much lignin as possible. This is common in higher-grade or archival-quality paper. If you’re trying to preserve anything long-term, lignin-free materials are a safer choice. They help keep your collection from breaking down early or suffering damage from inside the material itself.

When shopping for storage boxes, folders, or any other paper-based products for preservation, always check if the material is lignin-free. If it’s not stated, assume it may contain lignin unless it also says it’s archival or conservation-grade.

 

M

Understanding Mil: A Key Thickness Measurement in Archival Materials

A mil is a very small unit of measurement. One mil equals one thousandth of an inch. It’s often written as .001 inch. So if something is listed as 2 mils thick, it’s .002 inches.

You’ll see this term used a lot when talking about plastic sleeves, polyester film, or other clear enclosures made for storing documents, photographs, or film. The mil rating tells you how thick and durable the material is. Thicker materials offer more support and are less likely to tear or wrinkle, but they also tend to be stiffer. Thinner ones are more flexible, but they might not protect as well against pressure or wear.

For example, a 3 mil polyester sleeve is pretty thin and works well for handling flat documents that aren’t moved much. A 5 mil sleeve gives more support and is better for fragile or valuable items that need extra protection. You might even see thicker options used for heavy-duty needs, like oversized maps or high-use archival material.

Knowing how to read mil thickness helps you pick the right enclosure for what you're storing. You don’t want to overdo it and risk bending or stressing the item, but you also don’t want something so thin that it doesn’t really protect anything.

 

N

What Neutral Means in Archival Storage

When a material is labeled as neutral, it means its pH is right around 7. That’s the middle point on the pH scale. It’s not acidic and it’s not alkaline.

This matters because materials with a neutral pH are stable. They’re not actively breaking things down or reacting with other items. They’re generally safe to use around delicate materials like paper, photographs, or fabrics, at least in the short term.

But neutral doesn’t mean protective. It won’t cause immediate damage, but it also doesn’t guard against acid over time. That’s where buffered or alkaline materials are more useful. If you’re storing something valuable for years, neutral might not be enough.

 

P

What Permanence Really Means for Archival Materials

Permanence gets thrown around a lot, especially with paper products. But it’s not as clear-cut as it sounds. You can’t measure permanence with a single number. It’s more about how resistant a material is to chemical breakdown over time.

When you see "permanent paper," that usually means the paper was made to last. Most of the time, it’s an alkaline paper produced under specific guidelines, like those set by ANSI (the American National Standards Institute). These standards focus on durability, acid-free properties, and other factors that reduce the chances of decay.

But even permanent materials have limits. If they’re stored in a humid room or near something acidic, they’ll still age and weaken. Permanence isn’t a guarantee. It’s a sign that something was built to last, but it still depends on how and where you store it. Long-term survival needs both good materials and the right environment.

How the pH Scale Affects Paper and Preservation

pH stands for the "presence of Hydrogen," and it measures how acidic or alkaline something is. The pH scale goes from 1 to 14. A pH of 7 is considered neutral. Anything below 7 is acidic, and anything above 7 is alkaline.

The closer a material is to 1, the more acidic it is. The closer it is to 14, the more alkaline. And these changes aren’t small. Every step on the scale means a tenfold difference. So, a paper with a pH of 4 is ten times more acidic than one with a pH of 5.

For preservation, pH matters a lot. Paper with a pH below 5 is considered highly acidic. It will yellow, become brittle, and fall apart faster. That’s why acid-free or buffered paper is used for storing anything valuable. The higher the pH (within reason), the better the material is at fighting off acidic damage.

Knowing the pH of a material helps you decide if it’s safe for long-term storage. If it’s too acidic, even short-term contact with other items can lead to damage.

What the Photo Activity Test (PAT) Tells You

The Photo Activity Test, or PAT, is a lab test used in conservation. It simulates what happens to a photograph over time when it's stored with certain materials. The goal is to figure out if a storage product, like paper, plastic, glue, or ink—will harm a photo down the line.

It does this by speeding up the aging process in a controlled setting. It’s like fast-forwarding time to see what kind of reaction will happen between your photos and whatever’s touching them.

This test is essential for anything that comes into contact with photographs, negatives, or film. Just because a material feels smooth or clean doesn’t mean it’s safe. Some plastics off-gas harmful chemicals. Some adhesives break down and leach into the image. Some paper types contain trace acids or optical brighteners that can trigger decay.

If a storage product passes the PAT, that means it’s been proven not to react in a way that harms photographic items. If it hasn’t been tested or fails the test, it’s risky to use around photos.

For photo preservation, always go with PAT-passed materials. It’s one of the few reliable ways to make sure your storage choices won’t quietly ruin your images over time.

What Polyester Means in Archival Storage

Polyester is a type of clear plastic that’s stable and safe for long-term use. It doesn’t break down easily, and it won’t react with the items it’s protecting. That makes it one of the most trusted materials for creating archival sleeves, covers, or enclosures.

The name “Mylar D” used to be the gold standard for this kind of plastic. It became popular because of its clarity and stability. But the company that made it stopped using that brand name and switched to a new one: Mellinex. Mellinex is still the same type of high-grade polyester. It works just as well for preserving paper, photos, or other fragile materials.

Even though Mylar D is no longer made, that doesn’t mean polyester has gone away. Other brands make uncoated polyester that’s also good for archival work. What matters is that the polyester is uncoated and chemically stable. As long as it doesn’t have added coatings or plasticizers, it will not react with what you’re storing. That makes it a solid choice for anything you want to keep protected over the long haul.

Why You Should Avoid Polyvinyl Chloride (PVC)

PVC is another type of plastic, but it’s one you want to stay far away from if you care about preservation. When PVC starts to age or break down, it gives off hydrochloric acid. That acid is bad news. It can slowly destroy paper, photographs, or other materials nearby.

You can often tell something has PVC in it by the smell. It has that strong plastic scent, like a new shower curtain. That odor is a sign that the plastic is off-gassing, which means chemicals are being released into the air. Those same chemicals can seep into your stored items and cause staining, fading, or brittleness.

This is why PVC should never be used in archival storage. It might look like it’s doing the job, but over time, it will damage the very items it's meant to protect. Always double-check what kind of plastic you're using, especially if you're buying sleeves, binders, or storage boxes. If it contains PVC, skip it.

What Makes Polypropylene Safe for Archival Use

Polypropylene is a much safer plastic when it comes to storing or displaying fragile items. It’s inert, which means it doesn’t react chemically with papers, photos, or film. That’s why it’s often used in photo sleeves, negative holders, or display pages in albums and scrapbooks.

It’s not as stiff as polyester, but it still does the job well. It’s clear, it doesn’t off-gas harmful chemicals, and it’s affordable. Polypropylene is especially popular for storing items that get handled often, since it’s more flexible and less likely to crack.

If you're putting together an archive at home or organizing old family photos, polypropylene pages are a safe option. Just make sure they’re not mixed with PVC or other harmful plastics. Pure, uncoated polypropylene is a solid choice for everyday preservation needs.

Understanding Polyvinyl Acetate (PVA) and Its Use in Adhesives

Polyvinyl acetate, or PVA, is a type of plastic that shows up most often in adhesives. If you’ve heard of PVA glue, that’s what we’re talking about. It’s clear, solid, and commonly used in bookbinding and conservation work.

Not all PVA adhesives are the same, though. Some are designed specifically for conservation. These are internally plasticized, meaning they’re flexible and don’t become brittle over time. That flexibility, along with chemical stability, makes them safer to use on items that need to last.

PVA glues used in conservation are also reversible in some cases, which means they can be undone without damaging the material. That’s a key factor in archival work. If you’re repairing a book or mounting something fragile, always make sure you’re using the right kind of PVA. Generic white glue isn’t the same thing.

What Preservation Means in Archives and Libraries

Preservation is the general term for everything done to protect and keep materials usable over time. It’s not just about physical care. It includes everything from storage conditions and handling practices to digital scanning and format conversion.

For example, if a library moves its collection to acid-free boxes and keeps the temperature and humidity low, that’s preservation. If a museum digitizes old photos to reduce wear on the originals, that’s also preservation.

Preservation is different from conservation. Conservation usually refers to hands-on repair or treatment. Preservation is broader. It includes planning, storage choices, and preventive care.

If you’re building your own collection, preservation is what helps you keep it safe without having to fix things later. Choosing stable materials, avoiding harmful plastics, and storing items properly are all part of it. It's about keeping things from getting worse in the first place.

 

R

Understanding Reversibility in Conservation Work

Reversibility means being able to undo a treatment or repair without causing any harm to the original object. In archival preservation, this idea matters a lot. Whenever a conservator treats a book, document, photo, or artifact, they try to use methods and materials that can be removed later if needed.

The reason is simple. As techniques improve or materials age differently than expected, someone down the line might need to fix or redo the treatment. If the original repair can't be taken apart without damaging the item, it limits future options and could make things worse.

But reversibility isn’t always a clear yes or no. It exists on a scale. Some treatments can be mostly reversed, some only partly, and some not at all. The key is to aim for the safest approach that still protects the object. Sometimes, a more permanent fix is needed to stop further damage, so conservators have to weigh the pros and cons.

For example, if a torn page in an old book is repaired with a water-soluble adhesive, it can be removed later by applying water. That’s a reversible treatment. But if a strong synthetic glue is used, it might not come off easily and could stain or tear the paper. In that case, the repair may protect the book short-term but limit future repairs.

Good preservation work respects the original item. Reversibility helps make sure nothing done today prevents better care tomorrow.

 

S

What Solid Board Means in Archival Materials

Solid board is a type of paperboard that’s the same all the way through. It’s made from one type of pulp or fiber blend, pressed into a thick, sturdy sheet. This is different from boards that are made by layering different materials together, like combination boards or laminated boards.

Because it’s uniform throughout, solid board offers even strength and consistent quality. It doesn’t have weak spots between layers or fibers that might pull apart over time. This makes it a strong, reliable choice for archival boxes, folders, backings, and other supports where durability matters.

Solid board is often used in conservation because it holds up well under pressure and resists warping. It can handle environmental changes better than some cheaper, layered boards that might split or bend when exposed to moisture or heat.

Another advantage is predictability. Since the material is consistent, it behaves in a stable, known way when cut, folded, or exposed to adhesives. That helps when precise work is needed, like building custom enclosures or creating mounts for fragile items.

 

T

Thermo Hygrometers and Why They Matter

Thermo hygrometers are tools used to measure both temperature and humidity inside a space. If you’re storing anything valuable like old books, photographs, letters, artwork, or any kind of fragile document, you need to know what the air around it is doing. That’s where these devices come in.

They help you understand if the room is too hot, too cold, too dry, or too damp. Any of those conditions can slowly damage paper, cloth, leather, and other materials. Over time, high humidity leads to mold. Low humidity dries things out and causes cracking. Big swings between warm and cold can make bindings split, adhesives fail, or materials warp and buckle.

To keep a collection safe, the environment has to stay stable. That means no big temperature changes and no spikes or drops in humidity. Thermo hygrometers make it possible to keep an eye on that.

Older versions were simple, but new ones are much more accurate. Today, you can buy affordable digital models that store data and track changes over time. These are called data loggers. They’re small, easy to use, and give you a clear view of what’s happening inside a storage room.

If you care about preserving anything over the long haul, regular environmental monitoring is non-negotiable. Thermo hygrometers give you that information in real time. They’re one of the simplest and most important tools in any preservation setup.

 

U

Protecting Your Collection from Ultraviolet Light

A UV filter is a material designed to block ultraviolet radiation from passing through light sources. Ultraviolet light isn’t visible to the human eye, but it’s part of sunlight and also shows up in fluorescent and incandescent bulbs. The problem is, UV light breaks down organic materials. That includes paper, cloth, dyes, inks, and photographs.

Exposure to UV radiation speeds up fading, yellowing, and overall decay. If you leave something under these light sources for too long without protection, it will change. You might not notice right away, but the damage builds up. Once it happens, it can’t be reversed.

That’s why UV filters matter. These filters can be added to the glass in frames, display cases, and exhibit panels. They can also be applied directly to windows, or used as sleeves around fluorescent light tubes. Anywhere light hits your items, you want a barrier in place to cut out the UV part of the spectrum.

Even in storage areas where lights aren’t on all the time, UV protection is still worth using. Sunlight coming in through a window, or even overhead lights that get switched on for just a few hours a day, will add up.

Keeping ultraviolet light away from your collection is one of the easiest ways to slow deterioration. You can’t stop light from doing damage completely, but you can limit it. Using UV filters is a smart move to make your books, documents, and artifacts last longer without fading or falling apart.