An excellent, simple filtering setup. Buy a standard plastic filtering funnel from Walmart's auto department. I prefer about a 6" dia. one that I can use for everything. For good refining filter papers, my favorite (and fairly cheap) is S&S 596. They may not make them any more. If they do, you'll have to order them from the factory. Second best and, the cheapest paper around, is S&S Sharkskin. Don't buy Whatman #42 or another company's equivalent. They're OK but, are expensive and, slow as molasses. A perfect size paper is twice the depth of the top part of the funnel. If you use coffee filters, you can buy big ones cheap from a restaurant supply. You can also buy big stainless spoons, for things like stirring stuff while burning small amounts or, for uses while working around nitric acid. Leave most of your money at home when going to a restaurant supply.
Get a very clean or new bucket. I don't like using soap to clean buckets, except to remove oils or grease. I use a Scotch Brite pad and water. Soap residue can generate much foam when doing reactions that foam even without using soap. One time, I filled 7, 7 gallon plastic trays with foam from 2 gallons of aqua regia. To get those heavy gold powder residues off of the inside of a bucket and into the filter, first cut about a 3/4" square of Scotch Brite. Put a squirt of water in the bucket and scrub the bucket with the wet pad. Rinse the pad and fingers into the bucket with water. Using a lab type squirt bottle - all others are worthless - tilt the bucket towards you and rinse down the inside of the bucket. Still maintaining the tilt, move it to the filter and rinse the gold from the bucket, into the filter. It doesn't all come out easily.
Get a square piece of 1/2" or 3/4" plywood, sized to cover a bucket. In the middle, cut a hole so that the funnel will sit in it with an inch or two sticking out the top of the board. Most of the funnel will stick out the bottom. Instead of plywood, you can cut a hole in the top of a bucket lid. If you're using coffee filters, open them up flat. Fold the circle in half. Fold it again but, this time, don't fold it all the way - stop about 1/2" short on a regular size coffee filter. Open up the paper so that it's cone shaped and place it in the hole in the bucket. Put it all on the bucket.
Before filtering, wet down the paper, slightly, with the squirt bottle. Pour in whatever you are filtering to near the top of the paper. Keep it filled.
When filtering most things with a lot of volume, like aqua regia solutions, it's much easier and faster to let it settle, siphon off as much clear solution as you can, and then filter only the remaining residues. When you learn how to do it, siphoning can eliminate 90% of your filtering time. Filtering is always the bottleneck in refining operations. There are many tricks to speed things up.
When you first start filtering things like aqua regia solutions or gold mud, some of the solids will almost always pass though the paper. After a while, the paper will start clogging and the solution coming through will run clear of solids. You can tell when it runs clear by observing the drips at the tip of the funnel. When the drips are running clear, transfer the board and funnel to another clean bucket and re-filter the stuff in the first bucket. If you don't do this while filtering aqua regia, your final gold will be off purity. It's a good habit to get into, no matter what you're filtering.
I always have 6 or 8 of these bucket/funnel setups going, for the various things that always seem to require filtering. They're cheap and are easy to make.
I've owned several vacuum filters in my lifetime but, for most things, I prefer the filtering setup like I've described above. Vacuum filters are expensive and are a pain to use. They pull the solids down tight on the paper and seem to clog fast, especially with things like solver chloride. With certain plastic vacuum funnel designs (Bel-Art comes to mind), it's almost impossible to get the paper to seal. But, when you're filtering very large volumes of unsettled solutions, vacuum filters can speed things up.
A friend of mine had a unique way of filtering large volumes. He put about 15 restaurant coffee filter papers into a plastic kitchen colander. When the top filter paper became clogged, he would carefully remove it, exposing a fresh paper. It was messy but, it worked pretty good.
Get a very clean or new bucket. I don't like using soap to clean buckets, except to remove oils or grease. I use a Scotch Brite pad and water. Soap residue can generate much foam when doing reactions that foam even without using soap. One time, I filled 7, 7 gallon plastic trays with foam from 2 gallons of aqua regia. To get those heavy gold powder residues off of the inside of a bucket and into the filter, first cut about a 3/4" square of Scotch Brite. Put a squirt of water in the bucket and scrub the bucket with the wet pad. Rinse the pad and fingers into the bucket with water. Using a lab type squirt bottle - all others are worthless - tilt the bucket towards you and rinse down the inside of the bucket. Still maintaining the tilt, move it to the filter and rinse the gold from the bucket, into the filter. It doesn't all come out easily.
Get a square piece of 1/2" or 3/4" plywood, sized to cover a bucket. In the middle, cut a hole so that the funnel will sit in it with an inch or two sticking out the top of the board. Most of the funnel will stick out the bottom. Instead of plywood, you can cut a hole in the top of a bucket lid. If you're using coffee filters, open them up flat. Fold the circle in half. Fold it again but, this time, don't fold it all the way - stop about 1/2" short on a regular size coffee filter. Open up the paper so that it's cone shaped and place it in the hole in the bucket. Put it all on the bucket.
Before filtering, wet down the paper, slightly, with the squirt bottle. Pour in whatever you are filtering to near the top of the paper. Keep it filled.
When filtering most things with a lot of volume, like aqua regia solutions, it's much easier and faster to let it settle, siphon off as much clear solution as you can, and then filter only the remaining residues. When you learn how to do it, siphoning can eliminate 90% of your filtering time. Filtering is always the bottleneck in refining operations. There are many tricks to speed things up.
When you first start filtering things like aqua regia solutions or gold mud, some of the solids will almost always pass though the paper. After a while, the paper will start clogging and the solution coming through will run clear of solids. You can tell when it runs clear by observing the drips at the tip of the funnel. When the drips are running clear, transfer the board and funnel to another clean bucket and re-filter the stuff in the first bucket. If you don't do this while filtering aqua regia, your final gold will be off purity. It's a good habit to get into, no matter what you're filtering.
I always have 6 or 8 of these bucket/funnel setups going, for the various things that always seem to require filtering. They're cheap and are easy to make.
I've owned several vacuum filters in my lifetime but, for most things, I prefer the filtering setup like I've described above. Vacuum filters are expensive and are a pain to use. They pull the solids down tight on the paper and seem to clog fast, especially with things like solver chloride. With certain plastic vacuum funnel designs (Bel-Art comes to mind), it's almost impossible to get the paper to seal. But, when you're filtering very large volumes of unsettled solutions, vacuum filters can speed things up.
A friend of mine had a unique way of filtering large volumes. He put about 15 restaurant coffee filter papers into a plastic kitchen colander. When the top filter paper became clogged, he would carefully remove it, exposing a fresh paper. It was messy but, it worked pretty good.
R (too long didnt read) on another one of your awesome posts but what do you think of a filter flask with buchner funnel and vac, goldsilverpro? Im new to the hobby and I met someone at back yard metal casting.com who is helping me out and learning me and he led me down the path of using chemistry glassware. Having only used this the one time I played with silver it ran well except for the small quantites i was using always getting stuck on the filter paper. Also either i need practice or a better was bottle but getting stuff from one container or another is needlessly time consuming at times it seems.
