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Weighty Marble Question


kbobam
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Was just reading a topic where a marble was described as 'extremely heavy for its size'.

This got me wondering. The marble in question was approximately 2 inches in size, so how

about we use that for a hypothetical question. If we took every two inch marble (or non-marble

glass sphere) that's ever been made, and weighed them, just how much variation would there be? :huh:

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For the sake of comparing apples to apples we need to remember that the total volume will affect the amount of variation and you're best to describe the variation in terms of percentages and not units of weight.

I would suggest using sodium borrosilicate or soda-lime glass as your standard. These are the most common. Soda-lime glass has a density of 2.52g/cm3.

A cubic centimeter is about the size of a peewee marble. I estimate that your 2" marble would be about 10 cubic centimeters, making a clear soda-lime marble weigh 25.2g

Leaded glass sounds like it would be a good bit heavier. Ingredients like "lutz", which is a metal powder will quickly increase the weight.

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It's a good approach, but my calculations yield ~173 g for a 2" soda-lime glass marble (68.64 cm3 and your s-l density). As for variation, it would really depend on glass density and additives, as suggested. A lead glass 2" could go well over 212 g. And small variations in size are significant - a 2.05 " s-l would be ~186 g.

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Yeah, I guess I was off a little(a lot, lolz) on my volume estimation.

You see what I mean about sizes and the large difference in weight. Going up in size linearly gives you an exponentially increasing mass.

You can compare a 1" marble to a 2" you just have to do it by first comparing the weight of each to a standard(soda-lime) and expressing their weight above or below average as a percentage.

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Originally I was approaching this with the idea of wondering whether a person could pick up different marbles

of a given identical size and say with confidence "Oh yes. This one is definitely heavier than that one!"

But you've both brought up some interesting points.

Hadn't thought about lutz or other compounds that might be in some of them.

And in practice, the idea that an almost unnoticeable increase in size could affect the weight significantly,

could certainly cause a person to think that a marble is 'heavy for its size'.

Was the one calculation actually 'off' on volume, or was it weight?

I made an on-line effort to try to find weights for various glasses, and the figures that people were stating

as 'fact' varied so wildly that it was just ridiculous.

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The weight difference between a 2" soda-lime marble (~173 g) and a 2" lead crystal marble (~186 g) is about a 7%. But it would be like trying to distinguish 34 nickels in one hand from 37 or 38 in the other hand based on weight. I am not sure I could do it.

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The one calculation that was "off" was my guess as to the volume of a 2" marble. I was tired and this thread got me thinking back to highschool when we weighed different spheres of different sizes, quite the same to what you are asking. Anyway I was thinking of the 3/4" or 1" acrylic spheres we used, in that regard I don't think I was off by much.

You are right, seeing the math it is quite obvious that a person is most likely to percieve a marble as being denser than it is by comparing one to another of close but not exact size. I could totally see a discussion over a rare sulphide being fake or not based on its percieved weight as compared with a known rare sulphide. Quite a dangerous situation for the parties involved if they don't realize.

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Ha! Sounds like you appreciate 'aesthetics' and 'technical stuff' at the same time!

I'm that way, and to be honest, it's sometimes a problem.

(Then again, there's little doubt that I worry about stuff more than I should.)

It's just so easy to look at something nice-looking and wonder why it makes you feel happy.

How much are you just 'letting yourself go' and appreciating it in a purely 'artsy-fartsy' way?

And how much are you enjoying the intricate physical details of how this object came to be?

Is either approach somehow more appropriate for any given situation? What's a proper 'balance'?

As often happens, I'm starting to make my brain hurt, so I'm going to shut up. ( :

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I guess for me marbles do satisfy in a couple ways. For one I like precision, like a tool with sharp well defined edges, or the wiring in my computer case being just so, in that way a marble being a perfect sphere is nice. On the other hand they are random and spontaneous, pick one out of a bag and you won't have any clue as to what it will look like. Marbles are kind of like a modern art piece in that they are for the most part splashes of color, and while the artist can pick the colors and the general area they will land he can not choose how they will mix. But on the other hand marbles are timeless, not modern, even the oldest stone marble if well polished would look great sitting on the dash of the sleekest sports car. Even if you picked out one hundred marbles you didn't like, sitting in a pile they would look good.

I dont understand most modern art, I guess I don't have too, the beauty of modern art is that it doesn't have to confine to any one persons idea of aesthetically pleasing. Each person is free to enjoy the piece they like with the relative security that no one else can criticize their choice. There are no definitions as to what modern art has to be, no one can tell you that the piece you like isn't "authentic" or that it doesn't fit the definition you want to give it. Marbles are the original modern art. All of this and yet I don't feel cliche describing them this way as I might if I were to let my self enjoy the details of some other type of art, I don't feel snooty doing it.

I guess you could say I love marbles.

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A density measurement is the only way to compare as far as I can see. Drop the marble in a measuring tube of water and see what the volume is, weigh on some accurate jewellery scales and calculate density g/cm3. Use a mm gauge to obtain the diameter and produce a table of results. I know the volume will be slightly different for same diameter marbles due to how spherical the marble is but a mean could me obtained for each "type" of marble. Just musing.

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A density measurement is the only way to compare as far as I can see. Drop the marble in a measuring tube of water and see what the volume is, weigh on some accurate jewellery scales and calculate density g/cm3. Use a mm gauge to obtain the diameter and produce a table of results. I know the volume will be slightly different for same diameter marbles due to how spherical the marble is but a mean could me obtained for each "type" of marble. Just musing.

Comparing the density of marbles is useful, especially when differentiating between types of ceramic marbles - clay, limestone, agate, stoneware, porcelain, etc. as well as distinguishing between makers. e.g. Standard Toy stoneware marbles are less dense than AMT stoneware marbles. But if you're going to estimate average diameter, you can forgo the water displacement measurement and calculate volume using the formula.

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You could make a table that will give you the density from average diameter and weight, and density can then be easily and quickly determined.

By the way, the formula indicates that the volume of a sphere is proportional to the cube of the radius (and hence diameter).

So a 2" marble, which is 4 times the diameter of a 1/2" marble, will have 4 X 4 X 4 or 64 times as much glass as a 1/2" marble.

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Thanks hdesousa, I was using the volume displacement method for the very reason that the marbles are not spherical with the diameter just being used as a reference size.

Exactly.

The water displacement method can give a precise measurement of volume, but since marbles are not spherical, you have to estimate the mean diameter in order to compare marbles, as you said. It would be just as accurate to estimate a mean diameter by using calipers and averaging several diameter measurements, forgoing the messy water business. But perhaps I misunderstood what you were saying...other than comparing density is the way to go.

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This reminds me of a thought I once had about the type of shooter you may use in tournament play. I would certainly hope that in a game where 9-15year olds compete that the parents wouldn't do this but you could get a ceramic marble of considerable weight. I went so far as to look up the highest density ceramic balls I could find, I believe it was a zinc oxide compound.

http://www.nationalmarblestournament.org/tournament-rules.html

That's a link to the rules. They state it has to be glass and can't be metal but I bet most judges would let you use a ceramic one. Granted if they got their hands on it they would certainly notice a weight difference. The balls I found were 3-4 times heavier than your average glass marble.

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http://www.ortechceramics.com/store/product.asp?prodCategory=17&prodSubcategory=22

21$+ shipping for a 3/4" ball. Looks like a gloss white glass marble to me. I am buying one when I get paid(shh....don't tell the wifey! Lolz). Maybe I can find one in black. One website had translucent ruby red ones but they were 2" spheres.

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This reminds me of a thought I once had about the type of shooter you may use in tournament play. I would certainly hope that in a game where 9-15year olds compete that the parents wouldn't do this but you could get a ceramic marble of considerable weight. I went so far as to look up the highest density ceramic balls I could find, I believe it was a zinc oxide compound.

http://www.nationalmarblestournament.org/tournament-rules.html

That's a link to the rules. They state it has to be glass and can't be metal but I bet most judges would let you use a ceramic one. Granted if they got their hands on it they would certainly notice a weight difference. The balls I found were 3-4 times heavier than your average glass marble.

Ball-mill balls (AKA Atlanta porcelains) are made of a Zn Al ceramic and are much denser than glass. Perhaps that's what you had found.

The rules also allow a marble ground out of stone. I have a small sealed wooden cylindrical container, not unlike some thimble holders, which was reportedly handed out to marble tournament competitors. It supposedly contains a hand ground German agate.

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I feel as though I must get a zirconia shooter.

Ha! That would be a fun 'special concept' marble to have!

Your 'density and legality' ideas have been very entertaining!

But you (and many others) know how marbles can be. ;)

So even though your motives are pure, this could still be a 'slippery slope'.

You could easily progress to absolutely needing to have a 'perfect diamond clearie'!

Bet that one would really go over well with the wife! :lol:

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Yeah, ball mill balls.... I saw those as well but they weren't spherical really. The link I posted was to a precision bearing, If I remember correctly.

I did also see a very nice ruby colored zirconia sphere but alas, it was 2". anything more than an eigth above 3/4" really doesn't interest me. And if it isn't valuable for it's antiquity or rarity, even though i may like the style and color, being over 3/4" means I probably won't buy it. large marbles are an annoyance to me, they are becoming such a pet peeve that at this point if I were to find a marble like this: http://www.phylliswall.com/.a/6a00d8341c4f7d53ef01901cbd2597970b-pi

but in 3/4" I would buy it over new tires for my car simply because you never see the most beautiful creations of todays glass artists in anything under 1.5"

Which brings us to that slippery slope.....My last slide ended about a year ago. What had started as 200$ out of my tax return ended up being 50-100$ a month for six months. And with prices on man made diamonds these days who couldn't justify a diamond taw? lolliez But yeah, I could never tell my wife, the biggest diamond I have gotten her is quite small, the ring as a whole is quite nice though.

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  • 2 weeks later...

Exactly.

The water displacement method can give a precise measurement of volume, but since marbles are not spherical, you have to estimate the mean diameter in order to compare marbles, as you said. It would be just as accurate to estimate a mean diameter by using calipers and averaging several diameter measurements, forgoing the messy water business. But perhaps I misunderstood what you were saying...other than comparing density is the way to go.

I've tinkered with this very question too some time ago, and came up with some data, provisionally. I went with digital calipers, and tried (this is all very problematic, you know) to find the greatest and least diameter, find the average, then get the mass in grams (two decimal places) and use the formula you reference to calculate a provisional volume in order to get the density. I did find some variation (I looked at only pre WWII mibs in this short study) in the density, something like a low end of 2.30 g/cm3 to about 2.72 g/cm3. For machine mades, most came in around 2.35-2.50 g/cm3, while a few ran a bit higher (some Master and Akro). Interestingly, all of the higher density marbles of over 2.60 g/cm3 have turned out to be transitionals, a mix of American and German, but I have had American transitionals also run low (2.42 g/cm3). Not surprisingly, Pelt Rainbos, and their extreme bubbliness makes these run lower in density, as expected, as the glass is replaced with gas in these examples. I also looked at runs of the same type of marble and found that there is also some variation there, but nothing that seems to be important. My wife, who has a good statistics background, ran some simple tests and found no workable significant diagnostic differences within and between groups/types of marbles. In a word, my initial conclusion was that density can't be used in any meaningful diagnostic way, but that there might be useful ranges of densities if enough were measured. Who knows,

I have some concern that these objects, imperfectly round as they are, might be difficult to get a very accurate volume on. I've measured several hundred densities of mibs in this way, but I haven't yet done many that I would like to check: slags, CACs, and swirls, of which, I think I haven't measured any yet. This takes a bit of time.

So, I guess, I would say, yes, they can vary a bit, and some actually are more dense than others..., but not sure a person could actually tell 'in hand.' John

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Has anyone mentioned measuring several marbles at once to minimize the effects of rounding errors?

You could take ten or twenty or more marbles of the same type and get the total volume using water displacement.

If you're just interested in the density of the glass then the diameters of the various marbles aren't needed.

Yeah, watery mess, and all. But that's my contribution to this topic. :)

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Has anyone mentioned measuring several marbles at once to minimize the effects of rounding errors?

You could take ten or twenty or more marbles of the same type and get the total volume using water displacement.

:)

That might be possible, but one problem is that, even for the same marble, there is variation in its construction, and mass. Curiously, when measured in grams to the hundredths position, 0.00g, similar mint marbles, maybe from the 'same run' will have different masses between them (when in mint condition). Also, volume displacement will give you, in the best case, a rounded number to the tenths position only accurately to the tenths position, as near as I can tell. I have graduated cylinders in my lab, but they have to be big enough to accommodate the marble, and then this causes the accuracy of volume measurements to fall. Not sure that I've seen how one could get to the 0.00 position in terms of volume (without cheating!), accurately, by this method. Why does this matter? Well, if I only took density calculation to the tenths because this is all I have for volume precision, then I lose accuracy and most marbles would run up or down and appear to have the same density, when in fact they are different. If one really wants to see how these vary from manufacturer or age, it is best to have as many decimal places that one can...hand calculating volume and mass to 0.00 will give greater precision. I know most people won't care, and that's OK! I still think it an interesting problem. John

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