# Sweeps burner- detailed wanted



## grainsofgold (May 15, 2008)

In Roland Loewens book - Small Scale Refining of Jewelers Wastes- he has a diagram for a sweeps burner made out of large diameter pipe that resembles an outdoor grill of sorts on Page 25. It is fueled by natural gas with an afterburner set up. 

The diagram is not detailed enough for me to follow to try to make one. Does anyone have more detailed plans for a sweeps burner like this one?

I would like to make one to slow burn buffing wheels and floor sweeps-

Thanks

Grains of gold


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## GeeDub (Feb 20, 2009)

Ghetto Sweeps Burner:

Take 1 large cast iron frying pan. Spread sweeps evenly around inside of pan. Add enough Methanol to make everything damp. toss in a match.

After it burns down, put pan on a grill with lots of charcoal. Light coals and fry the sweeps to make sure you oxidized everything. 

This works for polishing sweeps which generally do not have fines carried off in the air. (The wax from the polishing compounds melts first, and traps really fine stuff.) Something like dried paper towels with solution spills should be kept in an enclosed area with a screen above to stop paper floaters.


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## Harold_V (Feb 21, 2009)

Here's something to think about. 

I incinerated polishing wastes, filters, old buffing wheels and floor sweeps on a regular basis for over 20 years. 

I avoided cast iron like the plague. 

Here's why. It's desirable to raise the temperature of the ash near a red heat to insure you eliminate all traces of carbon. Hard to do when you're heating a cast iron pan. 

I had excellent success with old stainless pans, which are relatively thin, and resist oxidation well. Steel doesn't hold up well at all due to the excessive temperature. 

Harold


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## GeeDub (Feb 21, 2009)

Harold_V said:


> It's desirable to raise the temperature of the ash near a red heat to insure you eliminate all traces of carbon. Hard to do when you're heating a cast iron pan.


Actually, it's not hard at all. A pile of briquettes will get it dull red if the pan is placed directly on the coals. Also, most gas burners such as found on a home stove, will get a small to medium sized pan red hot. A gas fired barbecue will do it too, if the pan is close to the flame. Use a pan large enough to spread out the sweeps, do not pile them high in a cone. You want an even coat on the pan.

That being said Harold, _stainless is a good idea_. I was just suggesting the cheapest way to set up. A thin stainless pan will warp, and then the bottom can spring upon the next heating, bumping stuff out of the pan. A heavy stainless pan will cost more but will work fine. 
I guess the best idea is to pick up heavy stainless used stuff from the Salvation Army. In fact, that is what I did 2 months ago for some experiments i am doing.

BTW this is only for small lots. Large lots we just burned in out gas fired incinerator.


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## Harold_V (Feb 22, 2009)

GeeDub said:


> Harold_V said:
> 
> 
> > It's desirable to raise the temperature of the ash near a red heat to insure you eliminate all traces of carbon. Hard to do when you're heating a cast iron pan.
> ...


For the occasional incineration, perhaps. I refined on a daily basis, processing polishing wastes routinely. Charcoal would have been worthless in my case. 



> Also, most gas burners such as found on a home stove, will get a small to medium sized pan red hot.


Yes, they will, but only in a given area. I used burners exactly like you describe, taking advantage of 1 pound of natural gas pressure (my natural gas service was installed to serve my refining business----it was not the typical 4 ounce delivery). I adjusted the flame to maximum, strictly for incineration. When the pan was as hot as it was going to get, and burning had subsided, it required torch heating to increase the temperature so remaining carbon would ignite. There were no exceptions. That was with thin pans. Cast iron would have been far worse. 



> A gas fired barbecue will do it too, if the pan is close to the flame.


From my experience, I'd say that is a poor idea. Incineration causes dusting, and dusting results in losses. To incinerate without some means of capturing potential losses was not a good idea, and proven in practice by having a filtered hood. Cleaning out the hood on about a two year cycle resulted in a recovery of roughly eight ounces of gold. That does not take into account the amount of gold that was trapped in filters. 



> Use a pan large enough to spread out the sweeps, do not pile them high in a cone. You want an even coat on the pan.


I used the largest diameter pans I could acquire from second-hand stores. Always stainless. It was not unusual to have a yield of a half gallon of ash after incineration. 



> That being said Harold, _stainless is a good idea_. I was just suggesting the cheapest way to set up.


That's why I used stainless pans. Not only were they inexpensive ($1.00 maximum), but they are far easier to heat to redness. The amount of energy it would take to heat a cast iron pan is enormous, and playing a torch on one would most likely result in a cracked pan. Cast iron does not enjoy uneven heating, something that is very obvious to anyone that has done any cast iron welding. 



> A thin stainless pan will warp, and then the bottom can spring upon the next heating, bumping stuff out of the pan


Interesting comment, but not true in practice. Like I said, I used stainless pans for more than twenty years. Never had that problem, although they do tend to deform somewhat. 



> A heavy stainless pan will cost more but will work fine.


Not likely to be encountered. Stainless is a poor conductor of heat as compared to many metals. When they are thicker, they become less desirable. What you will encounter is stainless pans with copper bottoms, or even aluminum bottoms, on the outside, of course. They were not the best choice, due to the red heat I spoke of. 



> I guess the best idea is to pick up heavy stainless used stuff from the Salvation Army. In fact, that is what I did 2 months ago for some experiments i am doing.


Indeed! I did exactly that, then when the pans had finally corroded to the point of having a pinhole, they would be transferred to the stock pot, where they slowly dissolved, resulting in recovery of traces of values. 

Everything but the squeal was my motto. I was rewarded handsomely for my process methods. 



> BTW this is only for small lots. Large lots we just burned in out gas fired incinerator.


Depends on what you call small lots. I had only my hood for incineration, and it served me perfectly well for the entire run of my humble refining business (more than 20 years, including processing carpets). I processed thousands of ounces of gold. It's a matter of running more than one pan when necessary. It's like eating an elephant - a bite at a time. 

Harold


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## GeeDub (Feb 22, 2009)

Harold_V said:


> That's why I used stainless pans. Not only were they inexpensive ($1.00 maximum), but they are far easier to heat to redness.


Well, we won't get into a pissing match over this one... 
You liked stainless. I used cast iron, stainless, and even large steel campfire pans. They all worked. I just gravitated toward the cast iron over time. 

My instructions were for a cheap setup for a beginner. That is what most guys on this forum seem to want to do. Haven't seen the post where the guy says I have half a million to set up a refinery, what should I do? 

If you are doing polishing sweeps from individual jewelers, many will be small lots. I did each separately on a pan on a gas stove under a hood. Didn't have to always use the gas. Sometimes just alcohol was enough. Larger stuff like rugs, wood flooring, etc., went in the incinerator.

As far as dusting, the presumption was for setting up on the cheap. Working in a room away from the (high) window will have the dust land within the room. Every refiner should have a doormat outside of his refining area to wipe his feet on to recover dust and spills. The cheapest (free) is to go to a carpet store and ask for a few of the old sample pieces they have.
-Gee


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## GeeDub (Feb 25, 2009)

After reading through this topic again I have come to the conclusion that it may be confusing for people new to the game. Please understand that Harolds' and my methods are 2 different solutions to the same task. 
They also appear to be designed for people in different stages of ability, capitalization and equipment.
Since the topic began with a reference to a book designed for the casual jeweler, my suggestion was tailored to that level of use.
You may be tempted to take what you think are the best of both ideas and combine them, I do not believe this is a good idea. Parts of each are mutually exclusive. I do not think you can synthesize a new process by combining the 2. 
Let me "flesh out" some of the basic things in my method. I invite Harold to do the same, and provide more detail on his method for the inexperienced. I also realize he is a moderator and has to read and answer lots of posts, so we can only hope he gets some spare time.
Since polishing sweeps can be easily divided, you can easily try both ways, and make your own choice.

The post was about polishing sweeps, therefore my answer is tailored to polishing sweeps.
First, let me point out that for those sweeps (my method) you do not *need* to heat the pan on a stove after the alcohol burn. It is nice, and it does help, but in this particular case it is not *absolutely* necessary.
The carbon in those sweeps is generally from the waxes in the polishing compounds, the fiber from the buffing wheels, and the felt and wax from the lap wheel (if used). This carbon can be adequately burned with just an alcohol burn, it just will have to be repeated a number of times.
The other thing I want to point out is, unlike the other method, do not use a torch. It will only serve to blow metal out of the pan.
Choose a large shallow pan over a small tall one. If you have a lot of sweeps, use larger pans or break into smaller burns. You want to cover the pan evenly with a layer of about (a maximum) of 2 inches of unburned sweeps.
How much Methanol? Wet the lot totally. You don't want to make a soup, but there can be slight pools of alcohol in the depressions. The purpose of the alcohol is not just to burn the wax of the polishing compounds. It is also to raise the temperature of the mass so that it has sufficient heat content to support independent combustion of the cotton or felt fibers. Think of it as burning wood. You get the fire hot enough to create self sustaining embers which slowly oxidize. Before you get to the fibers, you have to burn off the volatiles. Think of them as like a candle. As the candle wax burns through capillary action, the wick also burns down because of the heat in the center of the flame. The alcohol, although being a low temperature flame, has enough heat to volatize the waxes, which burn alongside the alcohol adding BTU content and raising the temperature.
That is why I gravitated toward a cast iron pan. The pan will heat more slowly, but the specific heat of cast iron works to hold the heat and radiate it back to the mass being processed ensuring that it stays hot long enough to oxidize embers. In burning, it is not the temperature, but the heat content which is important.
There is no reason to stay and watch the burn, nothing spectacular is going to happen. You can leave the room and go have a cup of coffee. I had a small window in the door, so I could see when it was finished.
When it is done (no smoking or embers lit), the pan will still be warm. That is good. It won't be hot enough to spontaneously combust the next batch of alcohol. Smoking at the end of the burn is a sign another burn is needed. On each successive burn, the pan will be warmer because it will take you less time to turn over the burnt sweeps (assuming you didn't go walk the dog).
Take a large spoon or spatula. Break up any clumps you see by gently mashing them down and breaking them apart. Then turn over everything in the pan, so that what was on the bottom (and not as well burned) is now on the top. This is why you use a shallow pan, you want ambient air to reach the sweeps and burn as embers. Do not pick up and drop while you are turning, you're not mixing cake batter. The edge of the turner need never leave the pan. Check your technique, If you do the turning over a clean piece of sheetrock, and dust falls outside the pan onto the sheetrock, you are being too vigorous. If you choose to stir, be gentle, stirring will raise dust. Being gentle cuts down on dust. (If you vacuum your work area regularly, it's not that big a worry.)

Wet with alcohol, burn again, turn again.

Repeat again as needed.

Also note, if you do it in a closed room (with a window high and away, and the door closed), you don't need a fume hood to catch the dust. The amount of dust raised will be negligible, and you can vacuum the room every 6 months. I am presuming you are starting on a budget. Fume hoods aren't free. If somehow a few dollars worth of metal drifted out the window, how many lots would you process to break even on the cost of the hood? *I am not saying don't (ever) get a fume hood, I am just saying for this procedure, it is not your first priority.* I am inferring from the initial post, this will only be done a few times a year.

Methanol is not the only alcohol you can use. Use what you get cheapest. I used to buy out the chemical rooms at auctions. Got all types of alcohols for pennies a gallon. They all work. Some burn hotter than methanol.
-G


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## Harold_V (Feb 25, 2009)

Excellent presentation of your method. 

The method I pursued required a hood, plus a setup that is fire resistant. No accelerant was required. Because the temperature of the pan is critical, unlike your example, I can see why you felt cast iron served adequately. It would not be by the method I pursued, which included heating the pan to a dull red heat. My one attempt with an iron pan proved a failure, so I avoided them religiously from that point forward. 

You alluded to the hazard of heating the waste material directly with the torch, but that was not a problem in that a low velocity flame was used when that was necessary, so little, if any, dusting occurred. A direct flame was generally used only to ignite the heated material, which often would not self ignite. I also played oxygen on the material towards the end, insuring that any traces of carbon were consumed. It served as a measure of the completeness of the incineration process. If any pockets of carbon remained, they were readily identified. End product, assuming it was heavy in value, was a nice deep purple color, absent of black. The sole exception would be with materials from benchmen that used the green buffing compound instead of rouge and Tripoli. 

I'm not suggesting for a moment that my method is the only way to incinerate, but it provided a product absent of carbon. Not a bad idea considering carbon has the ability to absorb values, so eliminating all carbon was top priority for me. 

I designed my operation around incineration. Nothing got processed without seeing heat first, even if it was nothing more than to burn off oils that are common to items that have been handled. 

The one distinct advantage to my method is the ability to convert a pan full of waste to ash in short order. By heating the pan from below, the oils and waxes, of which you speak, liquefy, at which point they burn well. There is a reasonable amount of smoke, however, so this method would not be suited to processing without a hood. It could be performed in the open, but I was always concerned about losses, thus the filtered hood. 

Many of my customers sent their polishing wastes, along with filters, in a large plastic bag. In order to process the lot with minimal loss, I incinerated the bag. They don't burn well until they have been converted to oil, at which time they burn with a vengeance. That is one of the reasons I preferred the method I chose. 

I also benefited greatly by the excessive heating in that fiber glass filters were reduced to a fine dust easily. 

As you have alluded, assuming we were discussing polishing wastes, I, too, leached for values. I paid no attention to silver unless the material came from a silversmith. If so, my process was entirely different than for wastes from a goldsmith. I didn't process for silver in that case, giving the resulting waste material a heavy boil in HCl, then a series of rinses until the rinse was clear of color. At that point I processed for values. 

By giving materials of this nature a boil in HCl, the resulting pregnant solution will filter without issues. The difference in doing so, or not, was so pronounced that when I processed silver bearing materials, I'd remove silver with nitric, then I'd incinerate the solids once again, to kill the nitrates, then they would be screened a second time, then subjected to a boil in HCl to improve the handling qualities of the resulting solution. 

If readers don't get a single thing of value from these posts, the one thing they should understand and use is the HCl wash. It truly is the magic bullet one seeks when filtration is troublesome. 

Harold


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## lazersteve (Feb 25, 2009)

When I process bench sweeps I use a method like Harold's. I work outdoors because the amount of smoke is huge. I cover the stainless steel pan with a stainless steel grease splash guard to prevent stray embers from escaping the pan. I avoid breathing the toxic smoke by handling the frying pan with a long PVC pipe extension slipped over the handle of the frying pan. I only do this on a day when there is a strong wind and I process the lot in batches of 1 pound of sweep material or less.

Once the sweeps are reduced to fine ash, I pass the ashes through a stainless steel mesh to collect any metal objects, gemstones, and unburnt items. I re-burn the items that are combustible until the whole lot is a consistent color. I typically see purple or green ash as an end result of this process. I use an old paint brush to gently coax the ash through the stainless steel mesh.


I have a video of the entire process that needs editing and posting.

I'll try and extract some photos from the footage and post them here soon.
Steve


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## goldsilverpro (Feb 25, 2009)

We had a large steel box incinerator about 4' x 3' x 6' tall. We put the sweeps in large SS trays, about 4" - 6" deep, with a screen on them, and used a 50/50 mix of gasoline/diesel (or gasoline/kerosene) to burn the sweeps. We let everything cool and settle overnight before slowly opening the door. Very little was lost. After removing the tray, the inside was vacuumed. The ash was then ball milled, screened, and a magnet was used to remove the steel.

We ended up with what is known in the trade as "prepared sweeps". The sweeps were fire assayed for all PMs and these plus the oversize and magnetic fractions were sent to a large refiner. The settlements were excellent and their assays were within a percent, or so, of mine. I don't remember who the refiner was.

All sweeps were purchased and we didn't have to account to anyone.


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## GeeDub (Feb 25, 2009)

Harold_V said:


> If readers don't get a single thing of value from these posts, the one thing they should understand and use is the HCl wash. It truly is the magic bullet one seeks when filtration is troublesome.Harold


I know I have said something to the effect of "how many posts of I agree" does a forum need?. 
However, I have to say it here. 
Your one post here will save a newbie soooo much time, anger and frustration, that you deserve a medal just for posting it. A lot of guys will have trouble on their early sweeps leaches. My Commendations Sir.

I am also very pleased with the direction this post has gone. As we have shown, there are many ways to do these things. We now have several very distinct methods that newcomers can apply according to their needs and circumstances.


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## hosef (Mar 6, 2009)

Just a question. What is the purpose of incineration?


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## Harold_V (Mar 7, 2009)

hosef said:


> Just a question. What is the purpose of incineration?


To eliminate unwanted substances that can be troublesome, including carbon. Oils of all types are another example. Anything that is absorbent and combustible is another. 

Incineration just makes sense. It is ultra critical if you refine jeweler's wastes, where polishing compounds, hair, fingernails, bits of wood, string, buffing lint, cat hair, part of someone's lunch, and countless other substances and objects get included in the refining lot. 

Harold


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## grainsofgold (Mar 7, 2009)

cat hair, part of someone's lunch,


.......body parts of jewelers that didnt quite make the grade......


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## peter i (Mar 9, 2009)

...organic matter when refining dental waste!
[img:64:32]http://www.nordisk-forum.dk/images/smilies/icon_puke.gif[/img]


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## Noxx (Mar 9, 2009)

peter i said:


> [img:64:32]http://www.nordisk-forum.dk/images/smilies/icon_puke.gif[/img]



Where is that coming from lol ?


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## Harold_V (Mar 9, 2009)

peter i said:


> ...organic matter when refining dental waste!
> [img:64:32]http://www.nordisk-forum.dk/images/smilies/icon_puke.gif[/img]



Oh, yeah! But you have to be careful! It is common to find gold crowns that have been installed over teeth that have silver amalgam fillings. I highly recommed teeth be broken with a hammer before incineration to insure that one does not breath any mercury vapors. 

Harold


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## peter i (Mar 11, 2009)

@ Harold
Yes, dental waste is ugly in all aspects.

Should I do it again, I think I would start with a good long boil in strong sodium hydroxide to break down any organics. Then sort it carefully.
















Noxx said:


> peter i said:
> 
> 
> > [img:64:32]http://www.nordisk-forum.dk/images/smilies/icon_puke.gif[/img]
> ...



its a .gif like the others.

Right click it, "save as", then you can add it to the smiley-file.




Sorry for going off-topic! (I have a few others that I would not dare to add, even though it's tempting)


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## Harold_V (Mar 12, 2009)

peter i said:


> @ Harold
> Yes, dental waste is ugly in all aspects.
> 
> Should I do it again, I think I would start with a good long boil in strong sodium hydroxide to break down any organics. Then sort it carefully.


Excellent idea. One must consider the ramifications of dealing with dental wastes. Hepatitis C and AIDS being amongst the possibilities. 

Harold


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## Anonymous (Mar 15, 2009)

I understand and appreciated both process's in getting the polishing waste to the burnt and shifted state. Once all carbon and trash has been removed, Whats next. I saw a mention of a HCL wash, and something about a leach. Knowing this material will be full a different kinds of abrasive grit, can it be processed in one of the traditional manners. Which one is best. Too, my bench sweeps are about 80% volume boric acid ( flux dripping into my pan). What method is best for processing this, and do I need to remove the boric before processing.


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## Harold_V (Mar 15, 2009)

I processed floor sweeps, filters and polishing wastes together. After incineration, the glass filter material readily crumbles to dust. After screening and removing any large pieces for processing by inquartation, or discarding magnetic pieces (to the stock pot----which was where I sent saw blades after incineration and mulling in a mortar). That way if there are traces of values on the surfaces, they are not discarded.

Once I had the material screened, it was given a boil in HCl and water. I used a roughly 50/50 mix, using tap water. Cover the material by a couple inches. You have to be vigilant to keep stirring the material as it heats, so you don't get localized drying. The material will readily stick and bake on to the beaker if you don't keep it in suspension. Once that happens, you get a hot area that cracks when you stir the container again. Because the material can be difficult to stir, and will often break a large glass stirring rod, I used a fiber glass rod instead. It seems to work well, but I didn't leave it in the solution. It was used then removed each time to avoid subjecting it to boiling acid for a prolonged period of time. 

Be advised that this process puts some bad miles on your vessel. They get severely scratched from the abrasives included, and eventually fail from abrasion, but you can run a large number of batches before the beaker is lost. Also, don't use a beaker that has been through this process for precipitation. The roughed up surface of the beaker will make recovery of the precipitated gold very difficult. It tends to adhere doggedly to any scratches or other rough spots in the beaker when it is precipitated. 

After you have boiled the material for a given amount of time (I usually gave it about 15 minutes), it was removed from the burner, then the container filled with tap water and stirred well. It should be allowed to settle well because you are dealing with extremely fine particles of gold, which may not settle immediately. 

When the solution has settled well (next day is good), decant using a hose, then fill the container with tap water and stir well, then allow to settle once again. I did this routine until the rinse water was fairly clear of color. Often just one water rinse after the digest will be enough. 

When the final rinse has been decanted, add AR to the lot, using one ounce of nitric and 4 ounces of HCl for each ounce of gold you expect to recover. The color of the material is a fair indicator of concentration, but it can be deceiving as well. 

When you add the AR, you should see an instant change in color, from pink/purple to a creamy yellow color. That is a sign that you are dissolving the gold, so you can use that as a guide to needing more acid. A small excess is advised, and a low boil is also advised, so if any filings have found their way to your polishing wastes, they'll be dissolved as well. Even karat gold will cooperate, due to the small size. By the time enough hard silver chloride might form, the acid has penetrated the entire particle, so all of the gold should be liberated. 

Add a little water after the boil, stir, then allow solids to solution to settle. Your solution should be a rich orange/yellow color. 

After it has settled, decant the pregnant solution, then add more water and stir well once again. You can repeat this process until the rinse comes off testing barren. Get the remains in a filter, using a fast paper (I liked S&S Sharkskin), removing the last traces of fluid. 

The remaining dirt will still contain values. It will contain silver, and it may even contain tiny bits of un-dissolved gold, although it should not. It likely will contain traces of platinum if any was included in the lot. I saved it for future processing in cyanide, then it was sold. Even after two processes, it still had value. It's hard to get everything from so much dirt, so you will spend only the amount of time you feel appropriate. 

This process should recover the vast majority of the values. 

As for bench sweeps, I'm assuming you're discussing filings and other material that accumulates in the pan. 

Such material was incinerated, then screened. Large pieces of value were removed and inquarted for separate processing. Filings were cleaned with a magnet, then they were given a prolonged boil in dilute nitric. I used 70% nitric and used it at roughly 50/50 with tap water. I was not concerned about creating traces of silver chloride. If you are, use distilled or purified water instead of tap water. 

This process will dissolve some of the silver contained in the filings, but it may not dissolve all of it. The filings will be much cleaner after the boil, but certainly not clean. Because the solution from this process tends to be very dirty, it is the once case where I produced silver chloride instead of cementing the silver with copper. You may choose a different course. There is no right or wrong method in this case. User's choice. 

After you've rinsed the filings (until the rinse is clear), dissolve the material using AR at the same ratio as above. Again, use an ounce of nitric for each ounce of gold you expect to recover. Heat until everything is in solution (you should expect to see particles of abrasive, which will not dissolve). Finish up by the method of your choosing. I evaporated, using a button of gold to consume any free nitric acid. That it got reduced in size was evidence that I had not left any gold behind. 

Gold from filings tends to be quite dirty after the first refining. You should find your now barren solution quite dirty, colored anywhere from a dark green to a dark blue color. Test it for platinum metals before discarding.

I found no problems from processing materials that included either borax or boric acid. The only big problem you may experience is if you try to filter the wash solutions. It is for that reason I suggest decanting (using a small hose). Most of these solutions are very difficult to filter, and there's no good reason you should have to.

Small hose: I used a short length of 3/8" ID vinyl tubing. It's easy to rinse, and is flexible enough to allow easy use. I used 1/8" wall thickness to avoid collapse of the tubing when making bends. You can prime the hose with water to begin transfer. Do not suck on the end with your mouth! :wink:

Hope this helps.

Harold


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## Lou (Mar 15, 2009)

Great post Harold. Thanks!


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## Harold_V (Mar 16, 2009)

Lou said:


> Great post Harold. Thanks!


High praise, coming from you, Lou! :wink: 

Thank you!

Harold


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## Anonymous (Mar 16, 2009)

WOW! thanks You answered all of my follow up questions as well. I am really excited about the refining process. My family are all jewelers and we have several shops, we have been getting the shaft for the last 20 years or so from our "guy". For the last several years I have been stockpiling sweeps, dust, plating solutions ect. , just about everything but hard AU scrap. I have always been a little leary of the acid after a bad burn as a kid, but the amount of material we go through demands more attention. Harold I sincerely thank you for your well detailed description, I can tell you really enjoyed your work and took pride in your end product. Regardless of which area of the precious metals field your in, love and pride in your work equals art. If I can ever be of any help to you, please let me know. Again thanks


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## Harold_V (Mar 16, 2009)

You're very welcome, Greg. If, when you get started, you need a little guidance, feel free to contact me, or to post your questions on the board, where others can respond as well. I always contribute my opinion when it comes to familiar territory. 

My entire refining career revolved around jeweler's wastes, so there's not much I haven't seen or processed. I don't claim to know it all, but I never found anything I couldn't process, including plating solutions and all kinds of wastes, including carpets. My experience is limited to gold, silver, platinum, palladium and retorting mercury. 

I truly enjoyed refining, but it, too, wore out its welcome due to prolonged hours in the lab. It's fun at first, but eventually becomes a chore. On an occasional basis, I think you'll enjoy every experience, and you'll be pleasantly surprised at the amount of value the waste contains. 

Harold


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## goldsilverpro (Mar 16, 2009)

Good article, Harold! Your method is probably the best way to do it.

As I have said before, I usually shipped the prepared sweeps, after incineration, ball milling, screening, magnetics removal, and blending and got pretty good returns on all metals from a large refiner (Heraeus, I think). I always fire assayed for all PMs before we shipped. We also shipped the magnetic fractions separately and always got a fair amount from them. We often bought large 200# lots of buffing dust from large jeweler manufacturers and preparing and shipping was the simplest, fastest way, although probably not the best.

I don't know how the large refiners handle the prepared sweeps. The old standard way was to melt it with lead (litharge) and other ingredients and then use large cupel furnaces to remove the lead.

One time, I experimented with direct flux smelting the prepared sweeps. The main problem was dealing with the Fe, Ni, and Cr oxides in the buffing compounds. I treated it like ore and and ended up with about 6 or 8 weighed flux ingredients. The flux was formulated by a detailed study of the fire assay texts. I remember it had quite a bit of fluorspar and silica in it. There was no lead. I think I used a little copper as a collector. I have the formula somewhere, but haven't been able to find it. It took a lot of flux - maybe 5 to 10 times the amount of prepared dust.

It worked well. Essentially, 100% of the Au, Ag, Pt, and Pd was collected. The slag was assayed and was totally barren. However, the experiments were small scale and were done in 30 gram assay crucibles. I never tried to gear it up. I just wanted to see if I could do it. The amount of flux could most probably be reduced with further experimentation. When I experiment, I often use a little overkill at first and then zero in on the right amounts later.


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## Harold_V (Mar 16, 2009)

goldsilverpro said:


> I remember it had quite a bit of fluorspar and silica in it. There was no lead.


That sounds similar to the flux formulation I came up with when I ran my waste materials. You were fortunate to have some manuals to which you could refer. I recall going to the UofU library, plus to the SLC Library to find anything I could on smelting. In the end, what I did was make a judgment on what I should use, all done by gut feel. I was lucky, for what I ended up with worked quite well. No prills, and slag that was so low in value that it wasn't acceptable to be processed with litharge. 

I found that part of extraction to be rather fascinating. It was always fun to mix together what appeared to be nothing more than dirt, and get back something of value. 

Thanks for the nice comments, Chris. 

Harold


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## Palladium (Mar 20, 2012)

Good read!


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