The Hidden Problem: Where Does the Gold Go?
One of the biggest frustrations for gold refiners—both beginners and experienced—is collecting the ultra-fine gold powder after the first precipitation with Sodium Metabisulfite (SMB).
This precipitated gold often forms nano-particles so small that they pass straight through ordinary filter paper (like coffee filters or cheap lab paper). As a result, you lose a significant amount of gold and end up with a contaminated filtrate.
Adding to the challenge, the reaction produces nitrogen gas bubbles. These tiny bubbles cling to the powder and make some of your gold float instead of settling, preventing a clean collection.
The solution is simple: follow a precise process of agitation, decantation, and advanced filtration to capture nearly all your gold before moving to the final refining step.
One of the biggest frustrations for gold refiners—both beginners and experienced—is collecting the ultra-fine gold powder after the first precipitation with Sodium Metabisulfite (SMB).
This precipitated gold often forms nano-particles so small that they pass straight through ordinary filter paper (like coffee filters or cheap lab paper). As a result, you lose a significant amount of gold and end up with a contaminated filtrate.
Adding to the challenge, the reaction produces nitrogen gas bubbles. These tiny bubbles cling to the powder and make some of your gold float instead of settling, preventing a clean collection.
The solution is simple: follow a precise process of agitation, decantation, and advanced filtration to capture nearly all your gold before moving to the final refining step.
Step 1: Solving the “Floating Gold” Problem
Before filtering, make sure all gold particles are fully settled.
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Initial Drop: Add SMB to your solution to precipitate gold.
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Critical Agitation (3–4 Hours Later): After precipitation is complete, gently stir the solution or carefully pour it into a clean container. This breaks the surface tension, releasing nitrogen bubbles stuck to the nano-gold.
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Settle Overnight: Once freed from gas bubbles, the gold sinks quickly. Let the solution sit undisturbed for at least 12 hours (preferably overnight) for complete sedimentation.
Before filtering, make sure all gold particles are fully settled.
-
Initial Drop: Add SMB to your solution to precipitate gold.
-
Critical Agitation (3–4 Hours Later): After precipitation is complete, gently stir the solution or carefully pour it into a clean container. This breaks the surface tension, releasing nitrogen bubbles stuck to the nano-gold.
-
Settle Overnight: Once freed from gas bubbles, the gold sinks quickly. Let the solution sit undisturbed for at least 12 hours (preferably overnight) for complete sedimentation.
Step 2: Decantation & Siphoning — The Key to Minimal Loss
Decantation is the most important step to avoid losing nano-gold. The goal is to remove almost all the liquid before it touches filter paper.
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Careful Pouring: Once the gold bed has settled, gently pour off the clear top liquid (filtrate) into a waste container without disturbing the sediment.
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Siphon Method: For more control, use a siphon tube positioned 1–2 inches above the sediment layer to remove liquid slowly.
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Hot Water Washing: After decanting, add hot de-ionized water, stir gently, let settle for a few hours, and pour off again. Repeat this wash 2–3 times to remove salts and acids.
After these washes, you’ll be left with a thick gold slurry—a small volume of liquid mixed with concentrated gold powder—making filtration much easier and safer.
Decantation is the most important step to avoid losing nano-gold. The goal is to remove almost all the liquid before it touches filter paper.
-
Careful Pouring: Once the gold bed has settled, gently pour off the clear top liquid (filtrate) into a waste container without disturbing the sediment.
-
Siphon Method: For more control, use a siphon tube positioned 1–2 inches above the sediment layer to remove liquid slowly.
-
Hot Water Washing: After decanting, add hot de-ionized water, stir gently, let settle for a few hours, and pour off again. Repeat this wash 2–3 times to remove salts and acids.
After these washes, you’ll be left with a thick gold slurry—a small volume of liquid mixed with concentrated gold powder—making filtration much easier and safer.
Step 3: Upgrading Your Filtration Setup
Only filter once your gold is concentrated into a slurry. Standard filters won’t cut it here:
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Fine-Pore Filter Paper: Use lab-grade paper such as Whatman Grade 42 or 44, designed to retain ultra-fine particles.
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Budget Option: Stack 2–3 coffee filters together to reduce pore size if lab paper is unavailable.
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Filter the Slurry: Carefully pour the thick slurry into your upgraded filter system. With little liquid volume, filtration is faster and the risk of gold loss is minimal.
Only filter once your gold is concentrated into a slurry. Standard filters won’t cut it here:
-
Fine-Pore Filter Paper: Use lab-grade paper such as Whatman Grade 42 or 44, designed to retain ultra-fine particles.
-
Budget Option: Stack 2–3 coffee filters together to reduce pore size if lab paper is unavailable.
-
Filter the Slurry: Carefully pour the thick slurry into your upgraded filter system. With little liquid volume, filtration is faster and the risk of gold loss is minimal.
Pro Tip: Save Money on Filters
If you refine regularly, consider buying large Whatman sheets (60 × 60 cm) and cutting them into smaller sizes. This is far more cost-effective than buying small pre-cut filters and ensures you always have high-quality paper ready.
If you refine regularly, consider buying large Whatman sheets (60 × 60 cm) and cutting them into smaller sizes. This is far more cost-effective than buying small pre-cut filters and ensures you always have high-quality paper ready.
Final Word
By applying these three principles—agitation, careful decantation, and fine-pore filtration—you can recover almost all of your nano-particle gold. Not only does this maximize your yield, but it also prepares you for the second refining stage where your gold reaches true high purity.
By applying these three principles—agitation, careful decantation, and fine-pore filtration—you can recover almost all of your nano-particle gold. Not only does this maximize your yield, but it also prepares you for the second refining stage where your gold reaches true high purity.
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