Storage Recommendations

A variety of harmful forces can affect collection objects in storage resulting in multiple forms of damage. For digital prints, the primary drivers of deterioration in storage are heat, moisture, and air pollutants, though each print type has its own unique sensitivities. Signs of decay include image fade, paper yellowing, ink bleed, and cracking or delamination of paper layers. Tables 1 and 2 show the types of damage that can result from each environmental factor on two broad categories of digitally-printed collection objects: photographs/fine art and documents/books. Control of temperature, humidity, and air quality can significantly extend the usable lives of these materials.

Table 1. Risk Factors For Digitally-printed Photographs and Fine Art

Risk Factor

Heat

Humidity Air Pollution

Evidence of Decay

Bleed

Cracking

Delamination

Yellowing

Bleed

Blocking

Cracking Curl/cockling Delamination Ferrotyping

Mold

Bleed

Cracking

Delamination

Fade

Yellowing

It should be noted that the sensitivities of digitally-printed photographs and fine art to damage are highly variable and product dependent. At times the behavioral differences between individual objects within a particular category are greater than those between categories. For example, photographs printed with two comparable dye inkjet printers using similar ink and paper types can have radically different deterioration rates due to subtle variations in colorant and paper formulations. For this reason, these objects should be treated as individually as possible with condition assessments made on a regular basis.

Table 2. Risk Factors For Digitally-printed Documents and Books

Risk Factor

Heat

Humidity Air Pollution

Evidence of Decay

Yellowing

Bleed

Mold

Yellowing

Damage to digitally-printed documents and books will mostly be in the form of paper yellowing. Because these objects are usually maintained for their information content as opposed to aesthetic value, some yellowing may be considered acceptable over long periods as readability will be maintained. For these objects, room temperature storage will suffice. For objects of high value, rarity, or on papers containing recycled materials or groundwood, cool to frozen storage will reduce yellowing rates helping to maintain the object’s original appearance.

Temperature and Humidity Recommendations

As with most collection materials, temperature and relative humidity (RH) drive the natural aging rates of digital prints. Extremes of either can cause significant damage that might not occur under proper storage conditions. IPI data has shown that, in the absence of pollutant gases, digital printing inks, dyes, and toners are fairly robust at room temperature and moderate humidity. However, many of the photograph and fine art inkjet printing papers can be prone to significant yellowing and deterioration of the ink receiver coatings. Lower temperatures can reduce these rates of decay. For this reason IPI recommends low-temperature storage for both dye and pigment inkjet photographs and fine art. For documents and books, some slight yellowing may be tolerated so room conditions will be sufficient. If yellowing would not be acceptable then cool to frozen storage is recommended.

The recommended maximum storage temperatures and relative humidity ranges for digitally-printed photographs and fine art are shown in Table 3. The recommended maximum storage temperatures and relative humidity ranges for digitally-printed documents and books are shown in Table 4.

Table 3. IPI’s Recommendations for Digitally-Printed Photographs and Fine Art Storage

Print Type

Maximum Temperature

Relative Humidity Range

Dye Sublimation

20°C  (68°F)

30-50% RH

Digital Electrophotography*

20°C  (68°F)

30-50% RH

Inkjet (dye and pigment)

4°C (40°F)

30-50% RH

 

Table 4. IPI’s Recommendations for Digitally-printed Document and Book Storage

Print Type

Maximum Temperature

Relative Humidity Range

Digital Electrophotography*

20°C  (68°F)

30-50% RH

Inkjet (dye and pigment)

20°C  (68°F)

30-50% RH

*For objects of high value, rarity, or on papers containing recycled materials or groundwood, a temperature of 4°C (40°F) at 30-50% RH may be used to minimize yellowing.
 

Humidity Extremes and Inkjet

High humidity should be avoided to prevent blocking, ferrotyping and mold growth. Inkjet dyes can also bleed severely when exposed to high humidity causing noticeable image blurring and color fringing. The graph below shows the time to bleed for a susceptible inkjet print at 25° C (77° F).  All conditions to the right of or above the line should be avoided. Prints should be safe below 65% RH. However, time to bleed rapidly diminishes as RH increases. Prints at 80% RH or higher can show noticeable bleed in less than 24 hours.

Dye Inkjet Bleed Limits

Very low humidity should also be avoided as it can exacerbate brittleness of some inkjet print layers making handling more risky. Like traditional photographs, digital prints should always be handled in RH conditions above 25%. This will be especially true for prints that have been on display because light and pollution exposure can further increase the brittleness of surface layers over time.

Simplified Multiple Media Storage 

Since few institutions can provide special storage areas solely for digitally-printed materials, these objects will need to be integrated with other collection assets. Fortunately, the basics of traditional paper and photograph care can, with a few exceptions, be applied to digitally-printed materials. The IPI Media Storage Quick Reference (MSQR) provides strategies on thoughtfully merging multiple traditional media types into four or fewer common storage conditions. This approach can be extended to include digitally-printed materials. The MSQR is available free for download from IPI.

Table 5 provides qualitative ratings for each material at each storage condition and Table 6 defines the rating system. The temperatures in Table 5 correspond to general storage categories from the IPI MSQR. These tables can be used to answer the fundamental questions: Are our current storage conditions adequate for digitally-printed materials?Or if not, what new environment would be optimal?

Table 5. Mixed Media Collections

Category

Temp F

Temp C

Digitally Printed Documents and Books*

Digitally Printed Photographs

Inkjet

EP

Inkjet

Dye Sub

EP*

Room

68°F

20°C

Good

Good

No

Good

Good

Cool

54°F

12°C

Very Good

Very Good

Fair

Very Good

Very Good

Cold

40°F

4°C

Very Good

Very Good

Good

Very Good

Very Good

Frozen

< 32°F

< 0°C

Very Good

Very Good

Very Good

Very Good

Very Good

*For objects of high value, rarity, or on paper containing recycled materials or groundwood, cool to frozen conditions may be used to prevent yellowing.

Table 6. Qualitative Rating System

Qualitative Rating System

No

Likely to cause significant damage

Fair

Does not meet recommendations but may be satisfactory for extended periods

Good

Meets minimum recommendations

Very Good

Exceeds minimum recommendations

Even though some digitally-printed photographs and fine art may be safe at room temperature, the highest common “good” or “very good” condition is 40°F (4°C) making this the optimal storage condition for the widest variety of these types of objects. For documents and books, room temperature will be adequate for most materials.

Air Pollution

Pollution comes from a variety of sources including the air within the storage environment, housing and framing products, adjacent collection materials, and even from within the object itself. Of these, the greatest threats to digital prints are air pollution and poor quality/reactive enclosures. Potential enclosure reactivity is addressed more fully in the Selecting Enclosures section of this website.

A variety of gases in the air can cause damage to digitally-printed materials. Oxidizing agents such as ozone can cause fade or yellowing of many print types as well as embrittlement of inkjet paper coatings. Nitrogen dioxide can induce yellowing in most print types and bleed in some dye inkjet prints. The reduced storage temperatures recommended above can help mitigate pollution-induced damage, but they are not equally effective for all gases. Nitrogen dioxide is strongly impeded, while ozone attack is only marginally slowed. Inert plastic enclosures, such as polyester sleeves, can be extremely helpful in reducing the rate of pollutant damage. Paper enclosures, even alkaline buffered, are poor barriers to air pollutants and should not be relied on for protection. A combination of low temperature, moderate humidity, and minimally permeable enclosures will provide the best solution for inkjet-printed photographs and fine art intended for long-term storage.

Managing the Storage Environment for Preservation: Sustainable Practice

A stated above, the storage environment has a significant impact on the preservation of cultural materials, and its careful management is an essential part of good stewardship. At the same time, the cost of energy to heat, cool, and control moisture can be a drain on institutional budgets. IPI has been active in developing and promoting sustainable practices for managing storage environments for many years. To learn more about IPI’s research, recommendations, publications and tools, visit: