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CYANOACRYLATE ADHESIVES, often called “super glue,” are
fast-curing, high-strength bonding agents that polymerize rapidly when exposed to trace moisture on surfaces. While they are valued for their speed and versatility, their
archival qualities — i.e., long-term stability, resistance to degradation, and suitability for preservation —
are limited compared to specialized archival adhesives.
Key archival considerations:
- Chemical stability over time:
Cyanoacrylates are generally chemically stable once cured, but they are not inherently archival grade. They can degrade under prolonged exposure to UV light, high temperatures, or certain solvents, which may compromise bond integrity over decades.
- Brittleness and impact resistance:
Standard cyanoacrylates are brittle and have poor shock or impact resistance, which can make them unsuitable for objects that may experience mechanical stress over time. This brittleness can lead to microcracking and eventual bond failure.
- Gap filling and substrate adhesion:
They bond well to many materials (plastics, metals, rubber, ceramics, wood, glass, paper, cloth, cement, tissue), but their poor gap-filling ability means they are best for flat, closely matched surfaces. In archival work, where surface irregularities or gaps may occur, this can limit their use.
- Environmental resistance:
They offer moderate resistance to water and heat, but archival materials often require long-term resistance to humidity, temperature fluctuations, and light. Cyanoacrylates are not designed for the extreme environmental stability needed in museum or library preservation.
- Reversibility and removal:
Once cured, cyanoacrylates are difficult to remove without damaging the bonded surfaces. This lack of reversibility is a major drawback in archival contexts, where non-invasive restoration or future disassembly may be necessary.
- Specialty formulations:
Some archival or conservation-grade adhesives use modified cyanoacrylates (e.g., elastomer-modified) to improve flexibility and reduce brittleness, but these are niche and not standard in consumer or industrial products.
Summary:
Cyanoacrylate adhesives are
not considered archival adhesives in the strict sense. They are fast, strong, and versatile for many applications, but their brittleness, poor gap filling, and lack of reversibility make them unsuitable for long-term preservation of sensitive or high-value objects. For archival work, specialized adhesives designed for flexibility, reversibility, and environmental stability are preferred.
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PARALOID B-72 is a thermoplastic acrylic resin (ethyl methacrylate–methyl acrylate copolymer) widely used in conservation for its
durability, reversibility, and resistance to yellowing. Its archival qualities make it a preferred consolidant and adhesive for cultural heritage materials.
Key archival properties:
- Chemical stability and reversibility – B-72 is a stable acrylic resin that does not require plasticizers to maintain durability, unlike cellulose nitrate. It is considered reversible in conservation, meaning it can be removed without damaging the underlying object.
- Non-yellowing – It resists discoloration over time, preserving the original appearance of artworks and artifacts.
- Adhesion and flexibility – It adheres well to a range of materials (ceramics, glass, wood, metal) and is more flexible than many other adhesives, allowing it to tolerate stress and strain without cracking.
- Durability – Once cured, it forms a hard, wear-resistant film that is stable under normal environmental conditions.
- Compatibility – It is compatible with vinyl, cellulosic, and silicone resins, and can be used as a barrier layer to protect against pollutants and moisture .
- Environmental resistance – It is insoluble in water and oils, and its water absorption is minimal, making it suitable for use in varying humidity environments.
Limitations to consider:
- Requires careful preparation and application to avoid compromising working properties.
- Solvent choice (acetone is best) and ratios affect setting time and final film properties.
- Not all inks are compatible; some may be disrupted by B-72 solutions.
In summary, Paraloid B-72’s archival qualities—
stability, reversibility, non-yellowing, flexibility, and durability—make it a reliable choice for conservation work, provided it is handled and applied according to best practices.
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SHELLAC possesses several
archival and preservation-related qualities that make it suitable for long-term storage and use in sensitive applications.
1. Natural, non-toxic, and biocompatible
Shellac is a natural resin secreted by the lac insect, composed mainly of polyesters of polyhydroxy aliphatic and sesquiterpene acids. Its biocompatibility and non-toxic nature mean it is safe for use in food, pharmaceutical, and archival materials without introducing harmful residues.
2. Chemical stability and aging behavior
In its acid form, shellac is pH-dependent in solubility and undergoes aging, which increases its glass transition temperature and reduces acid value and solubility. This aging process can make it more rigid over time, which may be beneficial for archival applications requiring dimensional stability.
3. Water resistance
As a water-resistant resin, shellac can protect underlying materials from moisture ingress, a key factor in archival preservation. This property was historically used in wood finishes and electrical insulation to block moisture and maintain integrity.
4. Dielectric properties
Shellac has excellent dielectric properties, making it useful in archival electronics or as a protective coating for sensitive components.
5. Film-forming and adhesive strength
Its ability to form clear, adherent films and seal surfaces makes it effective for encapsulating or protecting archival documents, artworks, and objects from environmental degradation.
6. Biodegradability and sustainability
Shellac is biodegradable and derived from renewable sources, aligning with modern archival practices that favor sustainable, environmentally benign materials.
7. Historical and cultural relevance
Shellac has been used for centuries in coatings, insulations, and decorative finishes, giving it a proven track record in preserving materials over long periods.
Practical archival considerations
- Long-term storage: May require monitoring for stiffness changes due to aging.
- Environmental control: Stable in moderate temperatures and low humidity; avoid prolonged exposure to high heat or strong alkaline conditions.
- Application: Best applied in controlled environments to maintain clarity and adhesion.
In summary, shellac’s
natural origin, chemical stability, water resistance, and biodegradability make it a viable archival material for protecting and preserving a range of cultural and scientific objects, provided its aging and environmental sensitivity are managed.
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NATURAL HIDE GLUES — made from animal collagen extracted from hides, bones, and connective tissues—possess several properties that make them valuable in archival and conservation contexts.
Reversibility and Non-Destructive Repair
One of the most important archival qualities is
full reversibility. Unlike many synthetic adhesives, which undergo permanent chemical changes when they cure, hide glue bonds can be cleanly undone with heat and moisture. This allows conservators to disassemble and reassemble objects without damaging the original materials, preserving historical integrity.
Biodegradability and Non-Toxicity
Hide glue is
biodegradable and free from synthetic chemicals, making it safe for use on organic materials such as wood, leather, and plant specimens. Its natural origin also means it does not leach harmful substances over time, which is critical for long-term preservation.
Compatibility with Delicate Materials
Because it bonds without damaging the substrate, hide glue is ideal for
fine antiques, musical instruments, and botanical mounts. It adheres well to wood and other natural materials without causing discoloration or chemical degradation.
Aging Stability
While not as chemically inert as some modern adhesives, hide glue is
stable over centuries when properly applied. Its protein structure resists degradation under normal storage conditions, and its reversibility ensures that future conservation work can be performed without compromising the object.
Historical Authenticity
In archival and museum contexts, hide glue is often preferred because it is
historically authentic—it was used in the same way by craftsmen and conservators of the past. This authenticity supports the preservation of original materials and methods.
Limitations
Hide glue is not immune to environmental factors. It can be affected by high humidity, temperature extremes, and prolonged exposure to light. It also has a finite shelf life and can degrade over time, especially if stored improperly.
Summary
For archival purposes, natural hide glue’s
reversibility, biodegradability, compatibility with organic materials, and historical authenticity make it a preferred choice for mounting, repairs, and conservation. However, its use requires careful handling and storage to maintain its long-term stability and effectiveness.
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NITROCELLULOSE CEMENT — a cellulose nitrate-based binder — has been used historically in archival and conservation contexts, particularly in early photographic emulsions, microscope slide sealants, and some early adhesives. Its archival qualities are shaped by its
chemical structure, physical properties, and long-term stability.
1. Chemical and Structural Basis
Nitrocellulose is formed by nitrating cellulose with a mixture of nitric and sulfuric acids, replacing hydroxyl groups with nitrate ester groups. The degree of nitration (nitrogen content) determines solubility, flammability, and mechanical behavior. For archival applications,
low-nitration grades (10.7–12.6% nitrogen) are preferred because they are less energetic, more chemically stable, and form durable, transparent films.
2. Film-Forming and Adhesion Properties
Nitrocellulose cements form hydrogen-bonded networks upon solvent evaporation, producing
clear, flexible films with good adhesion to glass, metal, and some plastics. This makes them suitable for sealing microscope slides, preserving photographic emulsions, and bonding archival materials.
3. Long-Term Stability and Degradation
- Stability factors: Properly purified nitrocellulose with stabilizers (e.g., diphenylamine) resists premature decomposition.
- Degradation risks: Over time, nitrocellulose can hydrolyze, especially in the presence of moisture, heat, or acidic byproducts. This can lead to yellowing, embrittlement, and loss of adhesion.
- Nitrogen oxide release: If residual acids remain, acid-catalyzed breakdown can occur, producing nitrogen oxides and further instability.
4. Environmental Sensitivity
Nitrocellulose is
highly flammable (flash point ~4.4 °C) and sensitive to heat, light, and oxygen. In archival storage, it must be kept in a
cool, dry, dark environment to minimize degradation and fire risk.
5. Archival Suitability
- Pros: Excellent clarity, strong adhesion, and ability to form thin, uniform films.
- Cons: Requires careful handling and storage; prone to hydrolytic and oxidative degradation over decades.
- Best use cases: Short- to medium-term preservation where transparency and adhesion are critical, and where environmental conditions can be tightly controlled.
Summary:
Nitrocellulose cement’s archival qualities are
good for adhesion and clarity but limited by long-term chemical instability. It is best suited for archival work when
low-nitration grades are used,
stabilizers are present, and
strict environmental controls are applied to prevent hydrolysis, oxidation, and fire hazards. For long-term preservation, modern synthetic resins or acrylic-based cements are generally preferred due to superior stability.
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POLYVINYL ALCOHOL ("PVA") ADHESIVES, formulated for conservation (i.e., marked as neutral ph) are widely regarded as
archival-grade materials due to their stability, reversibility, and compatibility with paper and other archival substrates.
Key archival qualities include:
- Chemical stability and inertness: Archival PVA adhesives are typically acid-free and do not off-gas once dry, making them safe for long-term use in collections. They are chemically stable under normal storage conditions and do not release harmful volatile compounds.
- Resistance to yellowing: Unlike some synthetic adhesives, archival PVA does not yellow over time, preserving the visual integrity of the bonded materials.
- Non-brittleness with age: When stored in appropriate conditions, archival PVA remains flexible and does not become brittle, which is critical for maintaining the structural integrity of paper and other materials.
- Lay-flat properties: PVA adhesives help minimize curling or waviness in paper by providing a strong yet flexible bond, which is important for preserving the original form of documents.
- Reversibility and re-treatability: PVA adhesives are considered reversible, meaning they can be removed or replaced without damaging the substrate, which is a key requirement for conservation treatments.
- Compatibility: They adhere well to most non-metallic surfaces and are suitable for use in mending, hinging, lining, and other conservation applications.
- Controlled drying: Archival PVA can be formulated to dry clear and flexible, and can be mixed with methyl cellulose to slow drying if needed arcare.com.
Conservation considerations:
- Always use archival-grade (Polyvinyl alcohol) PVA (acid-free, non-yellowing, non-brittling) rather than general-purpose PVAc (Polyvinylacetate,) which may contain additives that could be harmful.
- Store in a cool, dry place away from direct light to maintain stability.
- Avoid over-application to prevent cold flow or excess adhesive seepage into the substrate.
In summary,
archival PVA adhesives are stable, reversible, non-yellowing, and non-brittling, making them a preferred choice for long-term preservation in libraries, archives, and museums
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POLYVINYL ACETATE ("PVAc") adhesives are
not widely regarded as archival grade due to their instability, limited reversibility, and incompatibility with paper and other archival materials.
Key archival properties
- Chemical stability: Non-archival PVAc adhesives are not typically acid-free and non-offgassing (Oddy tested), meaning they release harmful volatile compounds that could damage sensitive materials. This is of particular concern with artifacts displayed in cases lacking adequate ventilation.
- Resistance to yellowing: PVAc adhesives may discolor over time under normal storage conditions, affecting the appearance of the bonded materials.
- Long-term stability: When stored in an unstable environment, archival PVAc may become brittle with age and lose flexibility.
- Reversibility: Although PVAc adhesives are considered reversible using isopropyl alcohol and/or heat, such reversibility is often difficult, depending upon the length of cure, which jeopardizes its safe removal or re-treatment if needed.
- Lay-flat properties: PVAc's water content may cause paper curling or waviness or raise wood grain, which interferes with maintaining the flatness of paper and wood surfaces.
- Compatibility: PVAc adhesive adheres well to most non-metallic surfaces.
- Drying characteristics: Many PVAc adhesives do not dry clear nor flexible. Neither Titebond Original, Titebond II, nor Titebond III dries clear, and the colors they dry to are influenced by their water-resistance qualities. Titebond Original dries pretty much to its light yellow color; Titebond II will be a darker shade of yellow, and Titebond III will dry to a dark brown.
Conservation suitability
Non-archival PVAc is
not approved for use by conservators. It is not considered safe for use on paper, board, and other non-metallic archival materials.
Storage and handling
PVAc adhesives should be stored in a cool, dry place away from direct sunlight and extreme temperatures.
In summary,
non-archival-grade PVAc adhesives are not sufficiently stable, reversible, non-yellowing, and non-offgassing, to qualify them as a reliable choice for long-term preservation in libraries, archives, and museums.
T
he adhesives I consider acceptable for use on a model include Roger's three "usual suspects" above, with some reservations, and some additions:
Titebond II (or equivalent PVA) for wood to wood adhesion.
Not suitable for paper or thread. Of all the adhesives I now use on models, I consider PVA to be the least acceptable.
Duco Original Formula nitro-cellulose adhesive for all purposes
only with a mechanical fastener. Reversible with acetone.
Polystyrene plastic (e.g. Styrofoam)
dissolved in acetone only with mechanical fastener - (equivalent to Duco Original Formula.) Reversible with acetone.
Clear shellac in a range of viscosities ("cuts") for all purposes, thin for sealing and for gluing paper-wood, thick for wood-wood but used as an adhesive only with a mechanical fastener. Easily reversible with alcohol.
Paraloid B-72 thermoplastic resin for all purposes except metal to wood, unless a mechanical fastener is used. (Used in a wide range of viscosities: thin as a finish coating through thick for adhesive.) Easily reversible with acetone. Full disclosure: I have not used B-72 as yet but expect I will be using a lot of it in the future. In recent years, B-72 has become
the "go-to" sealer and adhesive for professional fine art conservators, restorers, archaeologists, and just about anybody else in the business of putting lots of little pieces back together. (See:
https://en.wikipedia.org/wiki/Paraloid_B-72)
Liquid hide and fish glues for wood-wood, wood-paper. I avoid these because I find synthetic adhesives more agreeable to use, but they could be preferred for restoration work on antique models at times. (Reversable with hot water.)
CAVEATS:
I only use
epoxy resin adhesives when absolutely necessary because as a practical matter they are
not reversible. Examples of acceptable uses would be repairing a pinned broken spar, assembling small metal to wood subassemblies, or laminating lifts for a solid hull.)
I never use
cyanoacrylate adhesives ("Superglue") on models for the same reasons they are rejected as unacceptable by most all top-tier museum curation and restoration shops that now ban the stuff for a variety of reasons including, but not limited to a lack of easy reversal, poor shear strength, and archival uncertainties.
I have four overarching considerations when picking an adhesive for any particular purpose on a model, in order of importance with the most important first:
1.
Is it reversible and if so, how easily?
2.
What are its archival properties? How long will it last? Will it discolor over time? Does it have acidic properties that are detrimental to the model? Is it compatible with prior or subsequent finish coatings?
3.
How good is its holding power for the given application?
4.
How convenient is its "workability?" Does it dry too slowly, or too fast, or just right? Is its viscosity correct, or better yet, can its viscosity be easily adjusted? Does it require clamping or not?
With the exception of "the new kid on the block," Paraloid B-72, my above choices have been confirmed over the years by experience and keeping a close watch on the "state of the art best practices" of professionals in the fields of conservation and restoration. I am convinced without any doubt that the single most important quality of an adhesive used on a ship model is its reversibility. It isn't just that the builder may make a mistake that he wants to correct, but also, and perhaps more frequently, if (or when) the model suffers damage the repair of which requires deconstruction the damage can be repaired without further damaging the model.
I'm keenly aware there are those who will say, "I could care less how long the glue with which I build my models lasts as long as it outlasts me." I agree with them. If that's how they feel, there's probably no reason why their models need to last any longer than they do.
