Exploring Potassium Oxalate Developer: A Comprehensive Look at Its Use in Platinum and Palladium Printing

Potassium oxalate has long been a favored developer for platinum and palladium printing due to the unique aesthetic qualities it imparts to prints. Its ability to produce warm, rich tones and enhance subtle details makes it a go-to choice for many fine art photographers and printmakers.

However, as with many photographic chemicals, potassium oxalate has safety considerations that cannot be overlooked. This article explores potassium oxalate, including its benefits, potential risks, and best practices for safe handling.

Chemical Safety Disclaimer

The information provided in this article is for educational purposes only and is not a substitute for professional advice or training in chemical safety. Always follow the manufacturer’s safety guidelines, use appropriate personal protective equipment (PPE), and adhere to local, state, and federal regulations for handling, storage, and disposal of chemicals. Improper use of photographic chemicals can result in serious health risks or environmental harm. Consult a qualified professional or safety expert for guidance specific to your situation. The author assumes no responsibility for any injuries, damages, or violations resulting from the information provided.

What Is Potassium Oxalate?

Potassium oxalate, with the formula K2C2O4, is a chemical compound. It is a crystalline salt of oxalic acid and is commonly used in the photographic process as a developer for platinum and palladium prints. Its high solubility and chemical stability make it ideal for the controlled development of these prints.

As a developer, potassium oxalate reacts with the exposed light-sensitive platinum or palladium salts on the coated paper. This reaction reduces the metal salts to their metallic forms, creating the final image with unparalleled tonal range and depth.

Why Potassium Oxalate?

Potassium oxalate is prized for several reasons:

Warm Tones: Unlike some developers that yield cooler tones, potassium oxalate produces warm, brownish tones that enhance the richness of platinum and palladium prints. This characteristic is especially sought after in fine art photography.

Smooth Gradations: It provides smooth tonal transitions, allowing subtle details to shine, particularly in shadow areas.

Stability: The solution remains chemically stable over time, making it convenient for extended use.

Versatility: It works well with both platinum and palladium printing processes, making it a versatile choice for artists who work with both metals.

I recently made a new platinum/palladium print for my Solitary Witnesses project using potassium oxalate as the developer as shown in the video below.

If you enjoy slowing down with film, darkroom printing, and meaningful photography, consider subscribing to my YouTube Channel. I share new videos each week focused on simple tools, timeless techniques, and the quiet joy of analog.

On December 2nd, I shared a new video where I used the same calotype paper negative to make new prints using Ammonium Citrate and Sodium Citrate developers. All of the variables such as sensitizer formula, paper, developer temperature, etc. were identical for all three prints and the only difference in materials was the developers used.

The Toxicity of Potassium Oxalate

While potassium oxalate offers aesthetic advantages, its use carries inherent risks due to its toxicity. Understanding these risks is essential to effectively mitigating potential health hazards.

Toxic Ingestion: Potassium oxalate is highly poisonous if ingested. It can cause severe poisoning, leading to symptoms such as nausea, vomiting, and damage to internal organs, particularly the kidneys.

Skin and Eye Irritation: Prolonged or repeated contact with the skin can cause irritation. If it comes into contact with the eyes, it can lead to severe damage, including chemical burns.

Respiratory Hazards: Inhalation of potassium oxalate dust or fumes can irritate the respiratory tract, potentially causing coughing, difficulty breathing, or more severe respiratory issues.

Chronic Exposure Risks: Repeated exposure to potassium oxalate may lead to systemic toxicity, particularly affecting calcium metabolism in the body. It binds with calcium to form calcium oxalate crystals, which can accumulate in the kidneys and lead to kidney stones or renal damage.

Safety Considerations When Using Potassium Oxalate

To safely use potassium oxalate as a developer, it is essential to adopt stringent safety measures:

Personal Protective Equipment (PPE):

• Always wear nitrile or chemical-resistant gloves to prevent skin contact.
• Use safety goggles or a face shield to protect your eyes from splashes.
• Consider wearing a lab coat or apron to shield clothing and skin.

Proper Ventilation:

• Work in a well-ventilated space to minimize inhalation risks, ideally with a fume hood.
• Avoid creating dust or aerosolized particles when handling the powder.

Safe Handling Practices:

• Always mix potassium oxalate solutions slowly and carefully to avoid splashing.
• Store the chemical in a clearly labeled, sealed container away from children and pets.

Emergency Preparedness:

• Keep calcium gluconate gel or a similar antidote for potential skin exposure.
• Be aware of emergency procedures for chemical exposure, including rinsing eyes or skin with water and seeking immediate medical attention.

Proper Disposal:

• Do not pour used potassium oxalate down the drain without neutralizing it first, as it can harm the environment.
• Follow local hazardous waste disposal regulations to discard used solutions safely.

Alternatives to Potassium Oxalate

Alternative developers are worth exploring for photographers concerned about the toxic nature of potassium oxalate. I am beginning my tests with sodium citrate because I made deep, rich chocolate brown Kallitype prints with this developer. I have used ammonium citrate for platinum/palladium and will include it in my tests.

I will make a print with all three developers at the same temperature and then compare the prints. All other variables will be the same; the only difference between the three prints will be the developer.

Sodium Citrate:

• A less toxic option, sodium citrate produces cooler tones and offers a safer working environment.

Ammonium Citrate:

• Similar to sodium citrate but with slightly warmer tones, ammonium citrate is another viable alternative.

Custom Blends:

• Experimenting with blends of citrate-based developers can help approximate the warmth of potassium oxalate while reducing health risks.

While sodium citrate and ammonium citrate are considered safer alternatives to potassium oxalate for platinum and palladium printing, they still require careful handling. Both developers are less toxic but can still irritate the skin, eyes, and respiratory system if proper precautions are not taken. I always wear eye protection and an organic respirator when developing my platinum and palladium prints. I make a lot of prints, and I am exposed to them regularly, so I understand the possibility of long-term exposure and the potential impact on my health. For only $20, the respirator is a minimal price to protect your health. The replacement cartridges are readily available. Based on my unique conditions, I change my cartridges every 3 months. I also keep an extra mask as a backup to have on hand.

Sodium citrate, a mild irritant, can cause discomfort upon prolonged skin contact or inhalation of its dust, and it should be used in a well-ventilated area.

While less hazardous, ammonium citrate may release ammonia fumes during use, which can irritate the respiratory tract and eyes, particularly in poorly ventilated spaces. Always wear gloves and safety goggles to minimize risks and work in a well-ventilated environment.

Dispose of any waste solutions according to local environmental regulations to avoid potential harm to waterways and ecosystems. While these developers pose fewer health risks than potassium oxalate, they still require diligence and respect in handling.

Balancing Aesthetic Goals with Safety

Ultimately, choosing potassium oxalate comes down to balancing the aesthetic benefits against the potential health risks. Artists who work with this developer should prioritize safety and consider alternatives where possible. With proper precautions and an informed approach, enjoying the unparalleled beauty of platinum and palladium prints without compromising personal health is possible.

Conclusion

Potassium oxalate is popular for platinum and palladium printing because it produces stunning, warm-toned prints. However, its toxic nature necessitates a disciplined and informed approach to handling and use. By following safety guidelines and considering alternatives, artists can continue to create breathtaking prints while safeguarding their health and the environment.

If you have experience with potassium oxalate or other developers, please share your thoughts in the comments below. Let’s continue the conversation on safe and creative photographic practices.