Looking for advice counting sand particles

[gatorgrabber]

I'm looking for a better way to count the number of 800 micron sand particles in 1ml sample containers. I plan on using Image J software to do the actual counting and need a simple microscope setup to capture the required photo. The plan is to place the 1ml sample on a petri dish and add a bit of water to get separation of the particles. A 3-4" dish will give me plenty of room. Then, using the TBD microscope, taking a photo of the full sample plate for Image J to evaluate. This is a bit of a hostile environment (saltwater), so I can't risk expensive equipment. I was thinking about one of the low-cost digital scopes used for evaluating coins but I'm concerned that I can't pull back far enough to grab a photo of the entire sample plate. I have a colleague who actually uses a flatbed scanner for something similar. I'm afraid the harsh environment will make short work of one of those!

Any suggestions? Thanks!

[Hobbyst46]

ImageJ (as Fiji for example) does the job very well and, using the Watershed tool, can even identify individual particles that touch each other.

A flatbed scanner does the job very well and efficiently, at 600x600 dpi you can get an image of 1000-2000 grains. It will be about the same order of magnitude as the number of grains in your 1ml container. PROVIDED that the grains are large enough.

I presume from your post that the particles are ~800 micrometer diameter ? or was it ~800 particles, each of which is ~1 micrometer diameter ?

[gatorgrabber]

Thanks for getting back to me so quickly! For clarity, the individual particles are around 800 microns per particle. A 1ml sample usually has around 1800 individual particles per sample, which can vary widely. The scanner seems like a simple idea, I'm just concerned about killing it with leaked water getting into it. Still, it might be the better solution. I was hoping to find a low magnification, digital camera that I can use to aim downwards at the sample. Many that I've looked at so far have far higher magnification than I will require. I'm trying for a simple solution with as few moving parts as possible. Thanks!

[Hobbyst46]

For 800um particles, a scanner is really logical. For a microscope with even a 10x objective, the field of view diameter is ~20mm, so the number of particles in the image is too small.
Perhaps you can spread the particles on a sheet of white filter paper (or dark paper if they are white) for drying, then spread the loaded sheet on the scanner bed.

[gatorgrabber]

Excellent point regarding the limited field of view. I'll try a few more options with a scanner and see how it works out. Since what I'm doing is very basic, I'll just find a small/cheap scanner that I can easily replace if and when it gets soaked. Thanks again!

[MichaelG.]

I totally agree that using a flat-bed scanner is a near ideal arrangement.
… aside from anything else, they are flat-field and don’t suffer vignetting, so you should get good clean data.

If, however, the harsh conditions make it impractical … forget microscopes, and look for a “document camera” or “visualiser”

There are plenty to choose from, at a prices for every budget.

Just check-out the specifications, and preferably get a demonstration, before you buy.

MichaelG.

[gatorgrabber]

If the scanner just doesn't survive, I'll take your advice and look at the document scanners out there. Thanks for the advice!

[patta]

Since the sand grains are so large, I would sieve the sample and weight the fraction around 800 um.
Depending what else you have in the sample. It may be possible to simply wash the sample with a lot of water; the heavy sand particles aren't washed away and settle on the bottom. Dry and weight.

If you have only sand and water, you can weight the whole sample and calculate the % of sand (quartz) based on density

All the above because I believe that sand and saltwater are the worst enemies of optics and mechanics.

[ldflan]

Since the sand grains are so large, I would sieve the sample and weight the fraction around 800 um.
Depending what else you have in the sample. It may be possible to simply wash the sample with a lot of water; the heavy sand particles aren't washed away and settle on the bottom. Dry and weight.

If you have only sand and water, you can weight the whole sample and calculate the % of sand (quartz) based on density

All the above because I believe that sand and saltwater are the worst enemies of optics and mechanics.

At the risk of derailing the discussion a little, I just wanted to say that this thread and this particular post interest me a lot. They are interesting because they show that we have now gotten to the point where essentially disposable imaging and calculating machines, perhaps even cell phones that we carry in our pockets, can be used to count (in seconds) a large number of tiny objects of a specified set of dimensions or optical qualities such as sand grains in a properly prepared sample. That is some extraordinarily powerful technology!

Not 20 years ago, anyone tackling the problem would have done as suggested here - they would have isolated the grains from other components in a standard sample and calculated their number mathematically by first determining mass. But this takes a good deal of human effort (though it's far less and more reliable than having a human count grains of sand), and today (for now) it would probably be far more costly to hire a person to sieve, dry and weigh samples than it would be simply to sacrifice an old flatbed scanner to the cause.

I guess you could say that there is an interesting change in thinking about problem solving that comes along with the new technology. This is dramatically true, I think, in all sorts of ways...

[gatorgrabber]

I really appreciate the interest in this. I will be trying several different approaches to this issue over the next few days. Since there's a commercial aspect to this, it's important that a develop a solution that's both accurate and easy to teach to others. I'll report back regarding how it goes. Fingers crossed!

[MichaelG.]

As there is obviously some general interest in this topic … this is worth a look

https://www.petrog.com/ws2/steppingstage.html

Obviously, the present task can be fairly simply done in software, but these stages have a long and fascinating history

MichaelG.
.

Edit: __ I think this milestone also deserves a mention:
https://fdocuments.net/document/compute ... tml?page=1

[Hobbyst46]

Not 20 years ago, anyone tackling the problem would have done as suggested here - they would have isolated the grains from other components in a standard sample and calculated their number mathematically by first determining mass. But this takes a good deal of human effort (though it's far less and more reliable than having a human count grains of sand), and today (for now) it would probably be far more costly to hire a person to sieve, dry and weigh samples than it would be simply to sacrifice an old flatbed scanner to the cause.

Commercial grain processors and manufacturers of powder-based or grain-based products have already tackled this issue of the quantification of size distribution without recourse to old-fashioned sieving. Unfortunately, each method has its limitations. For example, think of sieving rod-shaped particles... Some detectors for on-line scanning of grains on a conveyor belt relay on two different camera sensors, one for coarse and the other for fine particles.

[MichaelG.]

Edit: __ I think this milestone also deserves a mention:
https://fdocuments.net/document/compute ... tml?page=1

.

In case anyone is inspired to build the little control board described in that document … I have roughly scaled the appalling photograph of the component-side.
.

5388B1CE-17A1-4E1B-AA08-F61B23C28DAE.jpeg (132.73 KiB) Viewed 1734 times

.

It only then remains for you to scale the tracks such that the leg-spacing on the chip is 0.1” [ 2.54mm ]
… a trivial job for any microscopist.

MichaelG.

[MichaelG.]

gatorgrabber

Acting upon my own advice [ ] I have purchased a 'Visualiser' and offer this image as a first proof-of-concept
.

Genee_crop.png (162.28 KiB) Viewed 1651 times

.
The device will handle "focus_free" subjects from A3 down to about the 33mm diameter of this plastic cell
... I have cropped the picture to enable posting here

the subject is some of the famous Dog's Bay foraminiferous sand

https://www.sandatlas.org/dogs-bay-in-connemara/

Even this visualiser [with is enormous range] shows potential ... so I am convinced that you could find something to suit your requirement.

MichaelG.