Please explain mesh

[2020hindsite]

I was hoping someone could please explain mesh sizes to me.
I see alot of people mentioning 100 mesh and others say -100 mesh?
For instance gold cube claims to catch 400 mesh... Would that be really big and not small?
I though +400 was huge and -400 was tiny?

What is the smallest speck you can see by eye in a gold pan? -400?

I'm not too concerned with learning bigger mesh sizes but I need to better understand fine gold sizing.
Thanks

 

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[nmhunter]

Mesh size refers to the number of holes in an inch. The gold cube for instance requires the use of a screen with 8 holes per inch, a #8 classifier. Anything that goes through the screen is -8 and anything that is larger than the screen is +8. I use 1/2 " or #2 classifier for my drywasher and then wash the larger material, +2, with a #8 to retain the -8 and process later with my Gold Cube.

If you stack several classifiers than you can run specific size materials and be very deliberate in your panning or maximize your use of something like a blue bowl. In a stack that has a #100 classifier followed by a #150 classifier the -100 and the +150 would be the same material.

Hope this helps

 

[Goodyguy]

Nm hunter nailed the answer.

Just so you are clear, if the material fits through a 100 mesh screen that means that it is -100 mesh. If the particles do not fit through a 100 mesh screen then they are +100

Of course you do not refer to half inch material as +100 even though technically it is. 1/2" material would be referred to as 2 mesh

Smallest you can see naked eye in a gold pan with 20/20 vision is around 400 mesh.

For more on the subject click the link: PARTICLE SIZE AND SHAPE DEFINED


GG~

 

[2020hindsite]

Thank you NM, I kind of understood then goody guy clearified beautifully.
So what mesh material is BEST to put through a 3 stack to catch all my 400 mesh?
I'm guessing -30 mesh?
Look at me talking in meshes!

 

[Goodyguy]

Thank you NM, I kind of understood then goody guy clearified beautifully.
So what mesh material is BEST to put through a 3 stack to catch all my 400 mesh?
I'm guessing -30 mesh?
Look at me talking in meshes!

-30 material is a good start to classify down to your +400 mesh material.

However going from +30 down to -400 would normally take 5 classifiers. Depending on your method of gold recovery you could get by with 3


The 3 stack would have results like this, considering you are starting with -30 material:

Top classifier 60 mesh ..... Particle size after screening = -60 to +150
Second classifier 150 mesh = -150 to +400
Bottom classifier 400 mesh = -400

As you can see the three stack leaves a lot to be desired as far as classification is concerned.
but Ok for running down a miller table.


The (preferred) 5 stack would have results like this:

30 mesh .....Particle size after screening = -30 material to +60
60 mesh = -60 to +100
100 mesh = -100 to +200
200 mesh = -200 to +400
400 mesh = -400

Much better when using a blue bowl for recovery

GG~

 

[2020hindsite]

Are you saying to recover all my gold down to 400 mesh size I need to run 5 separate classifications of materials through the gold cube?
I thought you could throw dredge cons classified down to -30 mesh into a gold cube and it could do the rest?
Is a blue bowl better at recovering very fine as long as I'm willing to classify?
Is there ANYTHING that requires little to no classification and will recover 400 mesh?
Bare with me and thank you goody guy so far

 

[nmhunter]

Glad it was helpful 2020.

I only use the 1/2 classifier on my dry-washer which is more of a grizzly than classifier and then a #8 classifier for material I will be running through the Gold Cube. So far, I do not have much need to classify smaller than that except on rare occasions when I have a large amount of ultra small material, time, and bad weather. I then screen down using scrap window screening before panning just to satisfy my itch.
I do plan to get a Blue Bowl and will follow GoodyGuy's advice on the 5 stack system, but currently plan to add a 150 mesh classifier. Not sure if that is over kill or if I need to also add something between 200 and 400. For now I just pan, remove gold and save the black sand cons for latter more precise processing.

Kevin in CO pans his -100 material effectively by hand. I also plan on trying that prior to getting the Blue Bowl to see if its cost is justified. I would rather save the funds and pick up a MD like the Falcon MD20 to eliminate the need to wash my drywashing rocks.

 

[Goodyguy]

Are you saying to recover all my gold down to 400 mesh size I need to run 5 separate classifications of materials through the gold cube?
I thought you could throw dredge cons classified down to -30 mesh into a gold cube and it could do the rest?
Is a blue bowl better at recovering very fine as long as I'm willing to classify?
Is there ANYTHING that requires little to no classification and will recover 400 mesh?
Bare with me and thank you goody guy so far

Sorry for the misunderstanding.

For the gold cube you can run anything under 1/8" (16mesh)
After running the gold cube you will be left with super concentrate that can be processed from there by panning. Or you can use any other method you choose to separate the gold from the concentrate.

Most methods require further classification to maximize efficiency. The blue bowl works best when all the particles being run are of the same relative size.

In fact all methods work best that way however most are not as sensitive as the blue bowl, such as a miller table but even then classification is the key to maximum efficiency.

[video=youtube;GU4YKblYctE]http://www.youtube.com/watch?feature=player_embedded&v=GU4YKblYctE#at=35[/video]


GG~

 

[2020hindsite]

Thanks, very helpful NM and Goody
So then why a blue bowl or why a gold cube over the other?
Is it just preference?
If the cube catches all 400 mesh from -16 mesh the why the need for the blue bowl?
It seems slower to do the same job...

 

[Goodyguy]

Thanks, very helpful NM and Goody
So then why a blue bowl or why a gold cube over the other?
Is it just preference?
If the cube catches all 400 mesh from -16 mesh the why the need for the blue bowl?
It seems slower to do the same job...

Not the same job.........

The gold cube is a super concentrator, it will not separate the gold from the black sand.
The blue bowl is a separator, with it you can eliminate everything lighter than gold leaving only the Gold.

Watch the above video to see how the Gold Cube works and also learn to do the rub your head pat your belly method of fine gold recovery using just a pan.

GG~

 

[nmhunter]

GG is right on. Very different jobs. The cube is a very effective concentrator. I save at least 5 buckets of concentrates screened to -8 then run them through the Gold Cube and end up with 1 pan of super concentrates. I then remove all the gold I can and save my concentrates to rerun later.

The Blue Bowl is used for very small amounts of material, about a cup full or less from what I have seen. You can then very precisely control the water flow and remove all the material leaving only your gold behind. Because of the fine tuning and precision you need all the material to be as close to the same size as possible to allow the specific gravity of each material to regulate how quickly it is washed up and out of the bowl.

 

[KevinInColorado]

Ok, here's the theory on the gap between each mesh size:

If you think about what gets caught in each screen...and therefore panned or blue bowled separately, it is a range of sizes from for example 1/50 of an inch down to just over 1/100 of an inch if using a 50 and a 100 mesh classifiers. So with that range of sizes, a 1/100 inch piece of gold is still heavier than a 1/50 inch piece of "other heavy stuff"...since gold has a specific gravity of 17-19 and silver/lead/iron based sands are s.g. of 5-9. We need the gold to be heavier than the particles around it so our finish separation process is not disrupted a a piece of non-gold blocking a lighter piece of gold from moving the way it should in our pan or crashing into a lighter piece of gold and pushing it when we want the gold to sit still. This teaches us that each mesh should be 2X the prior one and adding more screens wont really change much about the process beyond that..

Of course on the big end (low mesh numbers) none of this is relevant to finish processing...there it is about what works with your field equipment (2-4 mesh for a sluice, 8 for a gold cube...or no mesh for a Bazooka). At home I do 20 and 40 mesh separations after every trip and then once in a while I will take all the non magnetic heavies left over from my routine finish work and run it thru a 50 and a 100 mesh. I posted results from the 100 mesh recently to make the point that all you need to separate the -100 gold (and -200 remembering our relative weight discussion above) is a 100 mesh screen and a pan. With the shake and tap method, that's as quick as a blue bowl or slate table and almost as fast as a $4,000 shaker table...but not quite!

Oh and remember to enjoy the journey!

Ps: yes I know it is silly to go from 40 to 50 mesh but those are the screens I have right now...I could go from 40 to 80 but I don't have one of those...

 

[Oakview2]

Cube don't do that

 

[AZADAM]

I like mesh potatoes

 

[2020hindsite]

So I THINK I understand both mesh and the difference between the cube and the blue bowl.
My question now is why is the blue bowl necessary?
If you run buckets and buckets of dredge cons down to a few cups of super concentrate witha gold cube then why the blue bowl?
Who can't pan a few cups? It seems lazy to me, Why spend the money on a blue bowl instead of just panning what little bit comes out of the cube?
Am I missing something?

 

[KevinInColorado]

So I THINK I understand both mesh and the difference between the cube and the blue bowl.
My question now is why is the blue bowl necessary?
If you run buckets and buckets of dredge cons down to a few cups of super concentrate witha gold cube then why the blue bowl?
Who can't pan a few cups? It seems lazy to me, Why spend the money on a blue bowl instead of just panning what little bit comes out of the cube?
Am I missing something?

Both Mike Pung (co-inventor of the gold cube) and little ole me will tell you to go from cube to pan. However, panning fine gold is a skill that takes time to learn...and some people can't or won't do that.

 

[nmhunter]

I do not have a Blue Bowl yet and not sure when and if I will be getting one in the future. Lots of other items are higher on my priority list. Blue Bowls are very well liked by nearly everyone I have talked too, but with my extremely limited budget I still have not taken the plunge since I pan out VERY small materials even without the extra classifiers I would need to get anyway before the blue bowl would be effective.

 

[B H Prospector]

Hi 2020 and welcome. This is how I run my opperation. I classify 1/2" for my sluice or 1/4" for my drywasher. After I do a clean up and pan the cons into a safety pan to get the larger gold out I take the cons home for further processing with the blue bowl. I stack the following classifiers sarting with the top one first. 1/4" or #4 mesh, 1/8" or #8 mesh, a #20, a #30, a #50, and a #100. There is no reason to go any finer mesh than a 100 with a blue bowl as it will capture the smaller gold anyway if done properly unless you are into wasting money on extra classifiers. BTW before I do the above mentioned classifying I will let the cons dry and run a magnet through them to mremove as much of the magnatite as possible. Helps in the efficentcy of the bluebowl. That much less black sand.

Good Luck!

BH Prospector