How Climate Change Threatens Our Historical Photographs
The delicate beauty of 19th-century albumin photographs is facing a silent crisis, accelerated by the very air we breathe.
Imagine holding a historical albumin photograph from the 1870s. Its rich sepia tones and glossy surface offer a window into another time. Yet, this tangible connection to our past is increasingly fragile. As climate change alters our environment, it unleashes a complex web of pollutants and physical threats that accelerate the degradation of these irreplaceable cultural artifacts. The battle to preserve our visual history is now being fought against an invisible army of chemical compounds and shifting environmental conditions.
Albumin printing, the dominant photographic process from the 1850s to the turn of the 20th century, revolutionized how the world was documented. The process involved coating paper with a mixture of egg white (albumin) and salt, then sensitizing it with silver nitrate. This created the light-sensitive surface that produced the rich, detailed images treasured by historians and collectors today.
The very composition that gives these photographs their beauty also makes them vulnerable. The paper base consists primarily of cellulose, a natural polymer that forms the structural backbone of the image. The photographic emulsion layer containing silver particles is bonded to this cellulose foundation. When the foundation weakens, the image itself is threatened.
Albumin printing dominates photographic documentation
Paper base (cellulose) + Albumin coating + Silver nitrate sensitizer
Cellulose structure susceptible to environmental degradation
Climate change is not a single threat but a multiplier of existing risks to photographic heritage. Three primary pathways of damage work in concert to accelerate deterioration.
Rising global temperatures and humidity fluctuations create ideal conditions for physical degradation 1 .
VOCs emitted by photographic materials themselves accelerate degradation 3 .
Data adapted from study on American archives 9
Groundbreaking research has quantified how VOCs damage paper-based materials. A crucial 2023 study exposed paper samples to two common VOCs—acetic acid and hexanal—for 90 days in controlled environments to simulate long-term deterioration 3 .
Researchers employed a systematic approach to measure VOC damage:
The findings provided compelling evidence of VOC-induced damage, with different compounds attacking paper through distinct mechanisms.
| Property Measured | Reference Sample | Acetic Acid Exposed | Hexanal Exposed | % Decline (Hexanal) |
|---|---|---|---|---|
| Tensile Index | 45.2 N·m/g | 38.5 N·m/g | 31.8 N·m/g | 29.6% |
| Tear Index | 7.9 mN·m²/g | 6.8 mN·m²/g | 5.9 mN·m²/g | 25.3% |
| Burst Index | 3.6 kPa·m²/g | 3.1 kPa·m²/g | 2.6 kPa·m²/g | 27.8% |
| Parameter | Reference Sample | Acetic Acid Exposed | Hexanal Exposed |
|---|---|---|---|
| pH | 6.8 | 5.2 | 6.1 |
| Carbonyl Groups | 12.3 μmol/g | 18.7 μmol/g | 15.2 μmol/g |
| Degree of Polymerization | 1250 | 980 | 850 |
Understanding and combating photographic degradation requires specialized materials and methods. The following table outlines key reagents and their functions in preservation research.
| Reagent Solution | Function in Research |
|---|---|
| Sodium chloride | Controls relative humidity in closed vessels for accelerated ageing studies 3 . |
| Hexanal | Used in exposure experiments to simulate aldehyde VOC degradation effects 3 . |
| Acetic acid | Applied in studies to assess acidic VOC impact on cellulose-based materials 3 . |
| Cupriethylenediamine (CED) | Solvent for viscosity measurements to determine cellulose polymerization 3 . |
| Silver nitrate | Reference compound for understanding image metal deterioration in photographs. |
The experimental results demonstrated that hexanal was more destructive than acetic acid regarding mechanical strength loss, despite acetic acid causing a more significant increase in carbonyl groups (evidence of oxidation) 3 . This suggests that hexanal attacks the paper structure through different chemical pathways that more severely compromise physical integrity.
Confronting this multifaceted threat requires integrated strategies. As climate change continues to alter our physical environment, the need for proactive, science-based preservation strategies becomes increasingly urgent.
"Heritage is really the cumulative memory of humankind... It anchors us to place. It is something from which we derive our identity."
When photographic heritage is lost, we lose tangible connections to our collective past. The experimental evidence clearly demonstrates that invisible chemical threats pose real dangers to our photographic heritage. By understanding these mechanisms and implementing protective measures, we can work to ensure that future generations will still be able to look into the faces of their past.
The experimental evidence clearly demonstrates that invisible chemical threats pose real dangers to our photographic heritage. By understanding these mechanisms and implementing protective measures, we can work to ensure that future generations will still be able to look into the faces of their past.