Humidity for Long-Term Preservation

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Benefits

Maintaining a stable humidity is vital for long term preservation of materials and artefacts.

Prevents dimensional change

Consistent internal moisture levels avoids degradation from expansion and contraction.

Avoids corrosion and rust

Correct humidity prevents oxidation in metals and susceptible materials.

Prevents damage from pests

Proper humidity control can deter infestations and subsequent damage.

Humidity for long-term preservation
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Managing humidity to prevent dimensional changes

Any hygroscopic material has an internal moisture content that can be impacted by the atmosphere around it. If the air is too dry, moisture will move from the material to the air. If the air is humid, moisture can be absorbed by the material. When preserving objects in places like museums or long-term storage, these fluctuations in moisture content can cause microscopic dimensional changes to the object.

Over time these tiny dimensional changes will degrade an object’s integrity, particularly at the surface where the air has most impact. The result can be warping and cracking on an object’s exterior, loosening of joints, delamination of surface layers and separation of composite materials.

Humidifiers and dehumidifiers are vital to maintain a stable environment for long-term preservation. Understanding the ideal humidity for any given material is essential and once this is understood, any conservation programme must include a humidity management strategy.

Rapid fluctuation more damaging than extremes

When changes in humidity happen quickly, the material exposed to the air has less chance to adapt to changes in moisture content. If dimensional change occurs rapidly, it is much more damaging to the integrity of an object than gradual changes over time.

Leading authorities in the heritage sector recommend humidity in museums and galleries should not fluctuate more than +/-10%RH in any 24 hour period for this reason.

To acheive this, humidity control systems must be able to modulate accurately to changing needs of demand, increasing or decreasing their performance accordingly. Sensors and controls also need to be responsive. If a sensor has a +/-5% accuracy and a humidifier also has +/-8%, the complete drift in humidity control could potentially be +/-13%RH.

Preventing pest infestation damage with dehumidification

Pests such as silverfish and bookworms need a high humidity to thrive and breed. High humidity encourages mould growth, which is a food source, and softens organic materials such as paper and textiles, making them easier to consume.

Using dehumidifiers to maintain a humidity below 55%RH is important for preventing pest infestation. A temperature range of 18-22°C is also beneficial for long-term preservation of materials normally prone to infestation damage, such as books, wooden objects and textiles.

Using dehumidifiers to stop rust and mould

Corrosion risk increases for ferrous metals at humidity above 60%RH. At this level, surface moisture can enable the electrochemical reactions of oxidation. The higher the humidity, the faster these reactions occur, particularly in the presence of pollutants, such as salts that make the moisture more conductive.

The ideal level of humidity for long-term preservation will depend on the materials in question, but typically 35-55%RH is accepted as best practise for mixed collections that include metals.

Condensation occurs when air temperature drops to dew point. At this temperature, the air is saturated and can no longer hold water vapour, so it deposits on to surfaces. For instance, if the air is 20°C and 60%RH, any surface less than 12°C will collect condensation. It is important to understand the relationship between temperature, humidity and dew point for any long-term preservation strategy. Humidity control should be implemented to avoid this, not just to prevent rust but also mould growth on organic materials.

Stable humidity is vital in many industries for preservation

Humidity control for universities
Book old history document manuscript antique
Archives
Concert hall with symphony orchestra
Concert halls and organs
Picture Museum two women
Museums and art galleries
Military storage
Someone playing guitar
Musical instruments

Discover Condair in action

Projects and references

Steinway & Sons showroom, UK

Steinway & Sons has been renowned for producing the finest pianos since 1853. Passion and commitment, perfection and quality, reliability and “ of course “ an inimitable sound are just some of the characteristics people all over the world associate with these high-quality instruments. The impressive showroom in London Marylebone was recently refurbished. Condair™s steam humidifiers are playing a vital role in maintaining the exceptional craftsmanship involved in the production of Steinway™s famous pianos.
Condair in tune with Steinway

Henry Moore Foundation, UK

Two Condair RS steam humidifiers have been installed, by Ceilite Air Conditioning, at the prestigious Henry Moore Foundation in Hertfordshire. Henry Moore was a renowned artist, best known for his figure sculptures.
Henry Moore Foundation, UK

National Army Museum, UK

The National Army Museum is the leading authority on the British Army and its impact on society past and present. Condair has supplied and installed three Condair RS resistive steam humidifiers to maintain the humidity around the exhibits and archives.
The Nationa Army Museum, UK

Paul Klee Museum, Bern, Switzerland

The Kunstmuseum, Zentrum Paul Klee, is located in Bern, Switzerland, in the immediate vicinity of the Schlosshalde cemetery, where Paul Klee™s grave can also be found. The building is dominated by curved arches that blend harmoniously into the surrounding hilly landscape. It houses the comprehensive work of the Paul Klee Foundation and reflects the artist™s complexity through the division into three hills. The North Hill is dedicated to practical art education, conferences, and workshops. The Central Hill is used for collection presentation and temporary exhibitions, the South Hill for research and administration. Condair™s DL hybrid air humidifiers create an optimum indoor climate for visitors and the sensitive works of art.
Paul Klee Museum, Bern

Musée Atelier Audemars Piquet, Switzerland

The Musée Atelier Audemars Piguet invites visitors to explore the heritage of Swiss Haute Horlogerie. Combining striking architecture, living workshops, and a collection of over 300 timepieces, it offers a unique journey into the brand™s past, present, and future.

To ensure that visitors enjoy this journey in perfect comfort, Condair DL hybrid humidifiers maintain an ideal atmospheric humidity. This subtle yet essential technology protects the delicate timepieces on display while creating a pleasant environment for guests ” a perfect balance between preservation and well-being.
Audemars Piguet, Le Brassus - Switzerland

Foundation Michalski, Switzerland

An ideal work site for literature and literati &mdash that was the vision that Vera and Jan Michalski wanted to achieve with the Maison d'Écriture. It is located at the foot of the Vaud Jura Mountains, in the Bois Ditsert in Montricher, with a view of Lake Geneva and the Alps. The site was chosen for its scenic beauty and the quiet surroundings that are supposed to have a positive effect on writers' activities and inspire them to reflect. This location has a very special appeal and a unique atmosphere. Architects V. Mangeat and P. Wahlen were tasked with designing the architecture of the object. They created several buildings for the foundation's numerous activities that fit perfectly into the surrounding nature and form a kind of settlement. Individual living spaces for authors, a dining room, a recreation room, a large library for research, a room with modular space for exhibitions and an auditorium for all kinds of events promise numerous encounters and brisk cultural exchange. Condair DL hybrid humidifiers ensure comfortable atmospheric humidity.
Foundation Michalski in Montricher

Rjiksmuseum, Netherlands

The Rijksmuseum is one of the world™s finest art museums with over 1.5km of galleries and artworks by Rembrandt, Vermeer and Van Gogh. The Condair DL hybrid humidifier is maintaining the ideal humidity for the preservation of paintings such as The Night Watch, The Milkmaid and The Merry Drinker.
Rijksmuseum, Amsterdam - Netherlands

ARoS Aarhus Art Museum, Aarhus

The Aarhus Art Museum was founded in 1859. After several relocations, an architectural competition was held with the support of Queen Margrethe II for a new building, which was won by the Danish architectural firm Schmid, Hammer, and Lassen. The cube-shaped building, with a floor area of 52 by 52 meters and a height of 42 meters, has nine floors with 17,700 square meters of exhibition space, which is primarily dedicated to contemporary art.

The building is recognizable from afar thanks to the œYour Rainbow Panorama, a circular walkway on the roof with a diameter of 52 meters that shines in all facets of the color spectrum. Hybrid humidifiers from Condair ensure comfortable room humidity and preserve the value of over 1,100 paintings, 400 sculptures, and installations.
ARoS Aaarhus Art Museum, Denmark

Musée du Louvre, Paris

The Louvre Museum is a museum located within the Louvre Palace in the 1st arrondissement of Paris, France. It houses some of the most iconic works of Western art, including the Mona Lisa and the Venus de Milo.
With 72,735 m² of rooms and galleries, it is the largest art museum in the world, ahead of the Hermitage Museum (66,842 m²) in Russia and the National Museum of China (65,000 m²).

Various Condair humidity control technologies (Condair DL, RS, ME, DC) help maintain the ideal indoor humidity for the preservation of the exhibits and the well-being of staff and visitors. 
Louvre Museum France - Humidity control

Tongzhou District Library

The library provides free cultural information services such as literature borrowing, lectures and forums, exhibition exchanges, information consultation, youth activities, and cultural leisure to the public. The Condair BFP high-pressure humidifiers create a comfortable air environment for the reading room.

British Museum, UK

The British Museum first opened its doors in 1759, and is now one of the largest and most important culture and history museums in the world. In 1850, it moved to a larger building that was specially built to house its ever-growing collection. At the center of the classically-designed building is a covered square, with the former British Library building at its center. The roof was designed by the English star architect Sir Norman Foster, and is made up of 3,312 glass panes arranged in pairs. They cover the entire square, which at 76,500 square feet is the largest covered public square in all of Europe. Condair steam humidifiers on each of the museum's three floors ensure an ideal indoor climate for visitors and exhibits alike.

Columbus Museum of Modern Art, USA

The Columbus Museum of Art needed precise humidity control to protect priceless artworks and ensure visitor comfort. Condair installed its RS steam humidifiers, integrated with the museum™s HVAC system, delivering consistent humidity in the ideal 50¯Â±¯5¯% RH range. The system™s design allows rapid response to seasonal and daily fluctuations, ensuring paintings, sculptures, and historic artifacts are safeguarded against cracking, warping, or other moisture-related damage. Easy to operate and maintain, the RS units provide reliable, energy-efficient performance while blending unobtrusively into the museum™s infrastructure. By maintaining stable indoor humidity, Condair helps preserve the integrity of the collection, supports optimal conditions for visitors, and provides curators with confidence that their environment meets stringent conservation standards.

Mudac Museum, Lausanne, Switzerland

The mudac in Lausanne, designed by the Portuguese architects Aires Mateus, is an architectural masterpiece that houses two museums. The Museum of Design and Applied Arts and the Elysée Museum of Photography. Its architecture consists of two structures connected by a horizontal glass opening, giving visitors the feeling of being outdoors, no matter where they are in the building.

The upper part of the building rests on just three load-bearing points, which is an impressive feat of engineering and makes the upper structure appear to float. RS resistive steam humidifiers from Condair ensure a pleasant and healthy indoor climate and optimum humidity levels for conservation and value preservation purposes.

Quotes from our customers

Ceilite Air Conditioning

Tim Cheshire

Applications Engineer Technical Manager
We required an efficient and effective method of humidification that could safely raise relative humidity (RH) in a large archive store for priceless artwork – vital requirements that were successfully met by Condair. There were some challenges posed by the space to work in and the infrastructure of the building, but the excellent installation team overcame the issues without any complaint.

Would I specify Condair’s humidifiers again? Yes, without hesitation.
Opera North, UK

Richard Ashton

General Manager
The orchestra spends over 20 hours a week rehearsing and performing here, so it was essential to provide a consistent level of humidity during the times when they use the space. After meeting with Condair, we felt confident that the company understood our specialised requirement, not just the level of humidity, but also the need for reliability, flexibility and cost effectiveness.

Since installing humidification, which we switch on as and when required, our musicians have felt much more at ease regarding the safety and performance of their instruments.
Steinway & Sons, UK

Craig Terry

Managing Director
Incredibly rare and expensive wood is used in some of our models – but actually any type of wood is susceptible to changes in environmental conditions. Dryness is the enemy of pianos so humidity is really important. We need 40% to 50% humidity all the time to protect the wood, whether they’re in the showroom or the workshop. Condair’s units are ideal for the job.

And because we rely so heavily on the reliability of the humidifiers, we also contracted with Condair to service the humidifiers at regular intervals. Would I recommend Condair? Oh yes, they’ve supplied great service.

Frequently asked questions

What is the ideal relative humidity (RH) for material preservation?
How do seasonal changes affect humidity control?
Are there humidity control standards or guidelines for preservation environments?
Get free expert advice

If you want to explore your options for humidity control, Condair's expert sales engineers will visit your site, review your project and talk you through their recommendations.

Alternatively, if you would prefer a call or online meeting, our team are always happy to discuss possible solutions and offer free technical advice.

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