New Idea for Cleaning and Restoring Platinum-Palladium and Gold-Toned Van Dyke Prints: How to Eliminate Warm Casts and Stains Using Sodium Percarbonate

Over time, prints made with contact processes like platinum-palladium or Van Dyke Brown can manifest unexpected color alterations, but utilizing sodium percarbonate offers a reliable restoration protocol to eliminate warm casts and stubborn stains. What begins as a pure, neutral, cool black-and-white print can undergo a progressive “warming” of the highlights toward sepia tones over the years, sometimes accompanied by the appearance of localized brown stains or halos along the margins.

The Causes of Deterioration

The triggers for this phenomenon typically stem from two technical issues:

1. Insufficient or Too Rapid Final Washing: Microscopic residues of toning chemistry or acidic byproducts that were not thoroughly removed continue to react slowly with the paper over the decades.
2. Instability of Ferric Oxalate: In platinum-palladium processes, ferric oxalate historically represents the formula’s “Achilles’ heel.” Its natural chemical variability and sensitivity to storage conditions can generate unstable iron residues. These are responsible for color decay and typical oxidation stains (similar to foxing).

Using classic clearing agents (such as Kodak Hypo Clearing Agent or similar) proves completely ineffective on prints already altered by time. However, an insight shared within the international alternative printing community (and discussed on reference portals like AlternativePhotography.com by printers and industry experts like Sergio Devecchi—colleague of the Gruppo Rodolfo Namias circle—in his studies on recovering noble metal prints) offers a solution that is as effective as it is unexpected: the use of sodium percarbonate.

What Is Sodium Percarbonate and How Does It Work?

Sodium percarbonate is an eco-friendly powder compound (composed of sodium carbonate and crystallized hydrogen peroxide). Upon contact with warm water, it activates, releasing hydrogen peroxide and sodium carbonate.

• The Combined Action: Mild oxygenation coupled with a highly alkaline pH (similar to tetrasodium EDTA) allows it to break down organic oxidation byproducts. It also neutralizes unstable iron and acidic residues trapped within the cotton fibers of the paper—all without attacking the image formed by platinum, palladium, or gold.

The Operational Protocol for Print Recovery

Practical application requires close attention and a bit of “visual patience”:

1. Solution Preparation: Fill a tray with warm demineralized water (approximately 35°C / 95°F) and dissolve a calibrated amount of sodium percarbonate. A tested reference dosage is about 50–55 grams per 2 liters of water. Stir until a slight effervescence begins and the solution becomes slightly milky.
2. Immersion and Treatment: Use the solution at a temperature of around 25°C (77°F). Immerse the altered print and keep the tray under constant, gentle agitation (continuously for the first 2 minutes, then for about 10 seconds every 2 minutes). Treat for a variable time between 15 and 30 minutes, depending on the intensity of the stains.
3. Final Washing: After treatment, immediately transfer the print to a tray with running water for a prolonged wash of at least 30–45 minutes to remove all chemical residues and restore the paper’s neutral pH.
4. The “Psychological” Factor of Drying (Warning!): Immediately following the percarbonate treatment, the prints (particularly gold-toned Van Dykes) will appear to have lost their toning, looking brown and very washed out. This is a temporary optical effect due to humidity and the transient chemical reaction on the metal structure. Do not panic: as the 100% cotton paper air-dries over the following hours, it regains its original structure, and the stabilized original color (along with the original cool or golden tone) returns perfectly.

Frequently Asked Questions About Cleaning Alternative Prints

• Can sodium percarbonate damage platinum, palladium, or gold?
  No. The active oxygen action specifically targets organic stains, foxing, and paper oxidation. It leaves noble metals like platinum, palladium, and gold completely untouched and safe.
• Can I use commercial laundry sodium percarbonate?
  No. It is crucial to use 100% pure sodium percarbonate. Commercial laundry versions contain optical brighteners, perfumes, and surfactants that can permanently ruin fine cotton photographic paper.
• What should I do if the edge stains do not disappear?
  If the stains persist after 30 minutes, do not prolong the chemical bath. It is much safer to let the print dry completely and repeat the treatment the following day with a fresh solution.