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Author Topic: classifying screens  (Read 6814 times)

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Offline camper-2012

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classifying screens
« on: September 22, 2012, 02:47:44 PM »
 Does anybody know where I can find size 100 -150 - 200 mesh screening anywhere around Edmonton for classifying concentrates????

Offline overtheedge

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Re: classifying screens
« Reply #1 on: September 22, 2012, 06:06:31 PM »
You are aware that screening concentrates smaller than 60 mesh (250 micron) is tedious at best? I quit screening gold at 100 mesh (150 micron). Another thing to keep in mind is that you must screen in increments due to the fragile nature of the finer screens. A 200 mesh (75 micron) screen will hold water and 75 micron is just about the limits of unaided eyesight.

Never try to screen damp material: either wet or dry. When using screens damp material just plugs 'er up.
eric


Offline GollyMrScience

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Re: classifying screens
« Reply #2 on: September 22, 2012, 07:03:55 PM »
Bedrock Supply might have 100 and maybe 120 mesh but as overtheedge says its a pain to do by hand. Usually dry and a paint brush to swipe back and forth across the screens to aid passage. My lab sieves and tapping mechanism are way easier but way too expensive.
A company called Plainsman Pottery Supply - south side Edmonton - sell fine sieves for classifying powders. I use both their hand sieves (small 6.5" sieve that go 100, 120, 200) and a manual system that has a rotary paddle brush setup and fits in a five gallon pail for larger amounts -the sieve screens in it are removable to change sizes. I think its called the Talisman Rotary Sieve of something close to that. Its still a pain - just less of one.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline camper-2012

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Re: classifying screens
« Reply #3 on: September 22, 2012, 07:09:24 PM »
Greetings - Overtheedge - Thanks for the info, the reason I need the screening is that I want to get a screen fine enoegh to separate the flake gold from that real fine black sand. When trying to pan out the gold, the flakes like to skate around the pan and won't stay put so I can use the snuffer bottle to pick them up. The fine flour gold I don't seem to have a problem with. The concentrates come from the North Saskatchewan river.
    I do have a 20 mesh screen, so I thought that I would need something a lot finer.

Offline camper-2012

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Re: classifying screens
« Reply #4 on: September 22, 2012, 07:23:51 PM »
   Thanks - GollyMrSience - I'll have to give Bedrock a call & find out what screens they have. Also (I was thinking?) if I was to use varsol instead of water would the sand go through the screen any easier? (out in the open air though).

Offline GollyMrScience

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Re: classifying screens
« Reply #5 on: September 22, 2012, 10:56:20 PM »
The varsol will cause problems with gold floating and an unacceptable coating on grains when you try to clean them up after. Most solvents will cause problems one way or another.
I would suggest alcohol though.
Rum, Whiskey, Vodka, ...maybe wine. In a large glass to help keep the classifier operator lubricated as they sit there swishing dry grains around with a paint brush. Nothing worse than a squeaky classifier operator I say.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!

Offline coolshivers

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Re: classifying screens
« Reply #6 on: September 23, 2012, 11:14:28 AM »
bedrock has a few -100 left. Maybe a -70 not sure. I was there friday.
Piles of jobe sluices but limited classifier stock.
Me and the short guy still waiting on Tom's revision.  ;D

Offline camper-2012

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Re: classifying screens
« Reply #7 on: September 23, 2012, 12:27:16 PM »
Hello Deadwood - - maybe I should of explained it better. The gold settles to the bottom ok but then when I start working the black sand around and off the gold, the gold flakes (being flat and larger) seem to get caught in the current so to speak and skate or tend to move with the black sand before I can get all that real fine black sand moved. Its the real fine black sand that gives me trouble.

Offline camper-2012

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Re: classifying screens
« Reply #8 on: October 08, 2012, 11:38:46 PM »
at what point (size of classifier screen) can you retain the flakes in the screen and let only the flour gold and fine sand fall through.
                    Ken

Offline GollyMrScience

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Re: classifying screens
« Reply #9 on: October 09, 2012, 05:12:36 PM »
Hmmmm.... thats a bit like asking how high is up because what people call flour gold isn't a clearly defined size.
I can tell you in commercial practice I generally do a split on the 30 mesh wet screen and everything passing that goes to the shaker table.
If working with a clean up sluice or blue bowl then many operators add in one size finer - often 50 mesh. Some screen on narrower bands as well.
It depends on how picky your recovery system is.
A Miller Table likes to have stuff in splits like minus 30 plus 50 and minus 50 plus 100 and then a minus 100 for instance but since most recovery systems like sluices are wimping out pretty quick at the minus 150 mesh the need to get real fancy at the bottom end for the minority of the gold weighs against the work to get it.
For most of my work on even fine gold from sluicebox cons I have done ok on a minus 1/4 plus 1/8, minus 1/8 plus 16, minus 16 plus 20, minus 20 plus 30, minus 30 plus 50, minus 50 and only very occassionally a minus 50 plus 80 then a minus 80. I only very rarely ever haul out the 100 mesh because number one its a pain and number two the minus 100 seems to do ok recovery in the minus 80 split. Others may have a different take on the optimum splits from their experience.
Then again as I mentioned earlier on a shaker table I usually just head for a minus 30 split and take everything that passes the 30 as one fraction because the shaker is pretty forgiving.
What the heck - lets just keep mixin' stuff together till it blows up or smells REALLY bad!