Manufacturing Processes of Colloidal Metals at a Glance
What processes exist for the production of colloidal metals and where do the advantages and differences lie?
Colloidal metals such as gold, silver or platinum are produced using various methods. Each manufacturing process has its specific advantages and disadvantages, possible applications in the hobby sector and potential risks. Here is an understandable overview of the common methods.
Chemical production
In chemical production, metal ions are reduced to nanoparticles in a solution by reducing agents (e.g. sodium borohydride).
• Advantages: Precise control of particle size, high yield, suitable for laboratories
• Disadvantages: Contamination by chemical residues is a problem, which reduces purity. For the hobby sector, handling chemicals is laborious and expensive.
• Use in the hobby sector: Rare, as specialist knowledge and laboratory equipment are required
• Risks: Health hazards from chemicals and possible toxicity of the colloids if cleaning is improper
Low-voltage electrolysis (9–24 V)
Low-voltage electrolysis uses direct current between two electrodes (e.g. silver rods) in water to release metal ions; ionic solutions are produced (reactive ions). Some colloids can also form.
• Advantages: Simple and inexpensive, ideal for hobby users with silver generators
• Disadvantages: Mostly produces ionic solutions instead of true colloids, inefficient with metals that have high lattice energy (e.g. gold: only 1 ppm in 24 hours)
• Use in the hobby sector: Very popular, as devices are affordable and require no expertise
• Risks: Toxic compounds (e.g. silver nitrates) can form with impure water; hardly practicable with metals such as gold or platinum
High-voltage electrolysis (up to 10,000 V)
This manufacturing process uses higher voltages to dissolve more metal ions.
• Advantages: More effective than low voltage, can dissolve harder metals such as gold
• Disadvantages: Mainly produces ionic solutions, no stable colloids; high energy consumption
• Use in the hobby sector: Rather rare, as high-voltage devices are expensive and dangerous
• Risks: Risk of electric shock, instability of the solutions and reactivity of the ions with water
High-voltage plasma process (Bredig process)
In the high-voltage plasma process (1–10 kV), an arc vaporises metal under water into neutral nanoparticles.
• Advantages: True colloids, smallest particles (1–20 nm), high purity, effective for all metals. Proven since 1898
• Disadvantages: Complex equipment (e.g. high-voltage transformer), high effort
• Use in the hobby sector: Possible with construction instructions, but technical know-how and safety precautions are required
• Risks: Risk of electric shock, requirement for purest water, otherwise ineffective
Proton resonance process
This process uses vibrations to dissolve metal particles in water through “natural resonance”, without direct current flow.
• Advantages: High stability and small particle size (nano range), supposedly precisely controllable
• Disadvantages: Technical details are lacking, scientific evidence is thin, devices are expensive and not accessible
• Use in the hobby sector: Hardly possible, as it is proprietary technology that hobbyists cannot build themselves
• Risks: Unclear energy transfer; without a transparent presentation of the process, difficult to assess
Laser ablation
A laser beam vapourises metal in a liquid to form colloids.
• Advantages: Very pure, stable colloids, precise particle size, established since the 1990s
• Disadvantages: Expensive laser technology, high energy consumption
• Use in the hobby sector: Practically ruled out, as professional equipment is required
• Risks: Low, but improper laser operation can be dangerous (eye damage)
For hobby users, low-voltage electrolysis is the simplest option among the manufacturing processes, despite its limitations with hard metals and the restriction that only ionic solutions are produced. The high-voltage plasma process offers high-quality colloids and is feasible with effort, while laser ablation is reserved exclusively for professionals. The procedure for the proton resonance process is not sufficiently documented to allow reliable statements about it. Chemical production and high-voltage electrolysis are less practicable. Risks such as electric shocks or contamination should always be taken into account.
More on the topic: Production of colloidal metals
• Colloidal metals are not produced by electrolysis
• Differences between electrolysis and the high-voltage plasma process
• Colloids: Which ppm value is the most effective?
• Application and dosage of colloidal metals