Generally speaking most production refining uses a vacuum source for fast and relatively efficient filtering. I had posted a method to build a vacuum system but while that system is great for a production facility it is costly and beyond the means of many hobby refiners on this forum. There are alternatives to vacuum filtering which can give decent results and filter at a reasonable rate for a relatively small investment.
The answer to faster gravity filtration is a speed funnel. The secret to a speed funnel is in the inside surface of the funnel. If you were to fold a piece of filter paper and place it in a standard funnel the results are disappointing. As the liquid passes through the paper it has no place to go easily as the paper is snug up against the smooth glass inside of most funnels. A speed funnel solves this problem by providing small grooves on the inside surface of the funnel which allow the filtered liquid to drain from the funnel. A very simple concept but very effective.
Good rinsing is critical to producing fine gold and most contaminants to fine gold come from metal contaminated water that is not completely rinsed through the gold in the funnel. If the filtration is slow, the biggest contribution to contamination comes from the dirty water. While a speed funnel will never compare to a good vacuum with a buchner funnel it makes a world of difference over a standard smooth funnel.
Schleicher & Schuell (S&S) and Whatman make excellent filter papers for refining. Fold the papers in half to form a half circle and fold that in half again to form a shape of a pie. Then open to form a cone shape and place it in the funnel, a little water will hold it in place. A picture of a speed funnel is below, if you buy one get the biggest you can because it will hold a greater liquid volume. Measure the funnel from the rim down to where the liquid enters the stem of the funnel and double it, that is the biggest paper the funnel will take. S&S makes a paper called sharkskin which is a good general purpose paper with high wet strength. Whatman makes good papers in many grades and ashless which is great for melting the gold and burning off the paper with no residue.
Try it, you’ll like it.
The answer to faster gravity filtration is a speed funnel. The secret to a speed funnel is in the inside surface of the funnel. If you were to fold a piece of filter paper and place it in a standard funnel the results are disappointing. As the liquid passes through the paper it has no place to go easily as the paper is snug up against the smooth glass inside of most funnels. A speed funnel solves this problem by providing small grooves on the inside surface of the funnel which allow the filtered liquid to drain from the funnel. A very simple concept but very effective.
Good rinsing is critical to producing fine gold and most contaminants to fine gold come from metal contaminated water that is not completely rinsed through the gold in the funnel. If the filtration is slow, the biggest contribution to contamination comes from the dirty water. While a speed funnel will never compare to a good vacuum with a buchner funnel it makes a world of difference over a standard smooth funnel.
Schleicher & Schuell (S&S) and Whatman make excellent filter papers for refining. Fold the papers in half to form a half circle and fold that in half again to form a shape of a pie. Then open to form a cone shape and place it in the funnel, a little water will hold it in place. A picture of a speed funnel is below, if you buy one get the biggest you can because it will hold a greater liquid volume. Measure the funnel from the rim down to where the liquid enters the stem of the funnel and double it, that is the biggest paper the funnel will take. S&S makes a paper called sharkskin which is a good general purpose paper with high wet strength. Whatman makes good papers in many grades and ashless which is great for melting the gold and burning off the paper with no residue.
Try it, you’ll like it.
